LTM4605

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8055fbFor more information www.linear .com/L TM8055 TYPICAL APPLICATION FEATURES DESCRIPTION 36VIN, 8.5A Buck-Boost µModule Regulator The LT M®8055 is a 36V IN, buck- boost µ Module ® (micromodule) regulator. Included in the package are the switching controller, power switches, inductor and support components. A resistor to set the switching frequency, a resistor divider to set the output voltage, and input and output capacitors are all that are needed to complete the design. Other features such as input and output average current regulation may be implemented with just a few components. The LTM8055 operates over an input volt - age range of 5V to 36V, and can regulate output voltages between 1.2V and 36V. The SYNC input and CLKOUT output allow easy synchronization. The LTM8055 is housed in a compact overmolded ball grid array (BGA) package suitable for automated assembly by standard surface mount equipment. The LTM8055 is RoHS compliant. Buck-Boost Selection Table LTM8054 LTM8055 LTM8056 VIN (Operation) 36 36 58 VIN Abs Max 40 40 60 VOUT Abs Max 40 40 60 IOUT (Peak) 24VIN, 12VOUT 5.4 8.5 5.5 Package 15 × 11.25mm × 3.42mm BGA 15 × 15mm × 4.92mm BGA Pin and Function Compatible 12VOUT from 5VIN to 36VIN Buck-Boost Regulator

APPLICATIONS

n Complete Buck-Boost Switch Mode Power Supply n VOUT Equal, Greater, Less Than VIN n Wide Input Voltage Range: 5V to 36V n 12V/3A Output from 6VIN n 12V/6A Output from 12VIN n 12V/8.5A Output from 24VIN n Up to 97.5% Efficient n Adjustable Input and Output Average Current Limits n Input and Output Current Monitors n Parallelable for Increased Output Current n Wide Output Voltage Range: 1.2V to 36V n Selectable Switching Frequency: 100kHz to 800kHz n Synchronization from 200kHz to 700kHz n 15mm × 15mm × 4.92mm BGA Package n High Power Battery-Operated Devices n Industrial Control n Solar Powered Voltage Regulator n Solar Powered Battery Charging L, LT, LT C, LT M, Linear Technology, the Linear logo, µModule and Burst Mode are registered trademarks of Analog Devices, Inc. All other trademarks are the property of their respective owners. Maximum Output Current and Efficiency vs VIN VIN (V) OUTPUT CURRENT (A) EFFICIENCY (%)

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11.0k

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22µF 25V 68µF VOUT 12V 4.7µF 50V V IN 5V TO 36V fSW = 600kHz 36.5k 100k

8055fb For more information www.linear .com/L TM8055 PIN CONFIGURATIONABSOLUTE MAXIMUM RATINGS FB, V M 5°C (Note 1) BANK 2 VOUT A IOUT LL CLKOUT RT FB SS MODE SYNC COMP CTL K J LH G F E D C B BGA PACKAGE 121-LEAD (15mm × 15mm × 4.92mm) BANK 1 GND BANK 3 VIN TOP VIEW SVIN IIN RUN IINMON IOUTMON GND TJMAX = 125°C, θJA = 17.1°C/W, θJCbottom = 7.8°C/W, θJCtop = 17.5°C/W, θJB = 7.1°C/W, WEIGHT = 2.8g, θ VALUES DETERMINED PER JEDEC JESD51-9, 51-12 ORDER INFORMATION PART NUMBER TERMINAL FINISH PART MARKING* PACKAGE TYPE MSL RA TING TEMPERATURE RANGE (SEE NOTE 2)DEVICE FINISH CODE LTM8055EY#PBF SAC305 (RoHS) LTM8055Y e1 BGA 3 –40°C to 125°C LTM8055IY#PBF SAC305 (RoHS) LTM8055Y e1 BGA 3 –40°C to 125°C LTM8055IY SnPb(63/37) LTM8055Y e0 BGA 3 –40°C to 125°C LTM8055MPY#PBF SAC305 (RoHS) LTM8055Y e1 BGA 3 –55°C to 125°C LTM8055MPY SnPb(63/37) LTM8055Y e0 BGA 3 –55°C to 125°C Consult Marketing for parts specified with wider operating temperature ranges. *Device temperature grade is indicated by a label on the shipping container. Pad or ball finish code is per IPC/JEDEC J-STD-609.

• Terminal Finish Part Marking: www.linear.com/leadfree
• Recommended LGA and BGA PCB Assembly and Manufacturing Procedures: www.linear.com/umodule/pcbassembly
• LGA and BGA Package and T ray Drawings: www.linear.com/packaging http://www.linear.com/product/LTM8055#orderinfo

8055fbFor more information www.linear .com/L TM8055 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. RUN = 1.5V unless otherwise noted. (Note 2) PARAMETER CONDITIONS MIN TYP MAX UNITS Minimum Input Voltage VIN = SVIN l 5.0 V Output DC Voltage FB = VOUT Through 100k RFB = 100k/3.40k 1.2 V V Output DC Current VIN = 6V, VOUT = 12V VIN = 24V, VOUT = 12V 8.5 A A Quiescent Current Into V IN (Tied to SVIN) RUN = 0.3V (Disabled) No Load, MODE = 0.3V (DCM) No Load, MODE = 1.5V (FCM) 0.1 100 µA mA mA Output V oltage Line Regulation 5V < VIN < 36V, IOUT = 1A 0.5 % Output Voltage Load Regulation VIN = 12V, 0.1A < IOUT < 6A 0.5 % Output RMS Voltage Ripple VIN = 12V, IOUT = 3A 25 mV Switching Frequency RT = 453k RT = 24.9k 100 800 kHz kHz Voltage at FB Pin l 1.188 1.176 1.2 1.212 1.220 V V RUN Falling Threshold LTM8055 Stops Switching l 1.15 1.25 V RUN Hysteresis LTM8055 Starts Switching 25 mV RUN Low Threshold LTM8055 Disabled 0.3 V RUN Pin Current RUN = 1V RUN = 1.6V 2 3 5 100 µA nA IIN Bias Current 90 µA Input Current Sense Threshold (IIN-VIN) l 44 56 mV IOUT Bias Current 20 µA Output Current Sense Threshold (VOUT-IOUT) V CTL = Open l 54.5 61.5 mV mV I INMON Voltage LTM8055 in Input Current Limit 0.96 1.04 V IOUTMON Voltage LTM8055 in Output Current Limit 1.14 1.26 V CTL Input Bias Current VCTL = 0V 22 µA SS Pin Current VSS = 0V 35 µA CLKOUT Output High 10k to GND 4 V CLKOUT Output Low 10k to 5V 0.7 V SYNC Input Low Threshold 0.3 V SYNC Input High Threshold 1.5 V SYNC Bias Current SYNC = 1V 11 µA MODE Input Low Threshold 0.3 V MODE Input High Threshold 1.5 V Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: The LTM8055E is guaranteed to meet performance specifications from 0°C to 125°C internal. Specifications over the full –40°C to 125°C internal operating temperature range are assured by design, characterization and correlation with statistical process controls. The LTM8055I is guaranteed to meet specifications over the full –40°C to 125°C internal operating temperature range. The LTM8055MP is guaranteed to meet specifications over the full –55°C to 125°C internal operating temperature range. Note that the maximum internal temperature is determined by specific operating conditions in conjunction with board layout, the rated package thermal resistance and other environmental factors. Note 3: The LTM8055 contains overtemperature protection that is intended to protect the device during momentary overload conditions. The internal temperature exceeds the maximum operating junction temperature when the overtemperature protection is active. Continuous operation above the specified maximum operating junction temperature may impair device reliability.

8055fb For more information www.linear .com/L TM8055 TYPICAL PERFORMANCE CHARACTERISTICS Efficiency vs Output Current (12VOUT) Efficiency vs Output Current (18V OUT) Efficiency vs Output Current (24V OUT) Efficiency vs Output Current (36V OUT) Input Current vs Output Current (3.3V OUT) Input Current vs Output Current (5V OUT) Efficiency vs Output Current (3.3V OUT) Efficiency vs Output Current (5V OUT) Efficiency vs Output Current (8V OUT) TA = 25°C, unless otherwise noted. OUTPUT CURRENT (A) EFFICIENCY (%) 100

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OUTPUT CURRENT (A) EFFICIENCY (%) 100

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OUTPUT CURRENT (A) EFFICIENCY (%) 100

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OUTPUT CURRENT (A) EFFICIENCY (%) 100

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OUTPUT CURRENT (A) EFFICIENCY (%) 100

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OUTPUT CURRENT (A) EFFICIENCY (%) 100

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OUTPUT CURRENT (A) EFFICIENCY (%) 100

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OUTPUT CURRENT (A) INPUT CURRENT (A)

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OUTPUT CURRENT (A) INPUT CURRENT (A)

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8055fbFor more information www.linear .com/L TM8055 TYPICAL PERFORMANCE CHARACTERISTICS Input Current vs Output Current (24VOUT) Input Current vs Output Current (36V OUT) Maximum Output Current vs VIN Maximum Output Current vs VIN Temperature Rise vs Output Current (3.3V OUT) Temperature Rise vs Output Current (5V OUT) Input Current vs Output Current (8V OUT) Input Current vs Output Current (12V OUT) Input Current vs Output Current (18V OUT) TA = 25°C, unless otherwise noted. OUTPUT CURRENT (A) INPUT CURRENT (A)

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OUTPUT CURRENT (A) INPUT CURRENT (A)

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OUTPUT CURRENT (A) INPUT CURRENT (A)

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OUTPUT CURRENT (A) INPUT CURRENT (A)

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OUTPUT CURRENT (A) INPUT CURRENT (A)

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VIN (V) OUTPUT CURRENT (A)

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3.3VOUT 5VOUT 8VOUT VIN (V) OUTPUT CURRENT (A)

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OUTPUT CURRENT (A) TEMPERATURE RISE (°C) 100

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OUTPUT CURRENT (A) TEMPERATURE RISE (°C) 100

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8055fb For more information www.linear .com/L TM8055 TYPICAL PERFORMANCE CHARACTERISTICS Temperature Rise vs Output Current (24VOUT) Temperature Rise vs Output Current (36V OUT) Output Voltage Ripple, Unmodified DC2017A Demo Board 12VOUT Maximum Output Current vs CTL Voltage, Unmodified DC2017A, 12V IN Start-Up Behavior, DC2017A, 24V IN, 3A Resistive Load Temperature Rise vs Output Current (8V OUT) Temperature Rise vs Output Current (12V OUT) Temperature Rise vs Output Current (18V OUT) TA = 25°C, unless otherwise noted. OUTPUT CURRENT (A) TEMPERATURE RISE (°C) 100

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OUTPUT CURRENT (A) TEMPERATURE RISE (°C) 100

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OUTPUT CURRENT (A) TEMPERATURE RISE (°C) 100

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OUTPUT CURRENT (A) TEMPERATURE RISE (°C) 100

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OUTPUT CURRENT (A) TEMPERATURE RISE (°C) 100

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500µs/DIV NO CSS CSS = 0.022µF CSS = 0.22µF CTL VOL TAGE (V) OUTPUT CURRENT (A)

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(BUCK) 100mV/DIV 12VIN 6A LOAD (BUCK-BOOST) 100mV/DIV 6VIN 3A LOAD (BOOST) 100mV/DIV 8055 G240.5µs/DIV MEASURED WITH HP461N 150MHz AMPLIFIER

8055fbFor more information www.linear .com/L TM8055 PIN FUNCTIONS GND (Bank 1, Pin L1): Tie these GND pins to a local ground plane below the LTM8055 and the circuit components. In most applications, the bulk of the heat flow out of the LTM8055 is through these pads, so the printed circuit design has a large impact on the thermal performance of the part. See the PCB Layout and Thermal Considerations sections for more details. Return the RFB1/RFB2 feedback divider to this net. VOUT (Bank 2): Power Output Pins. Apply output filter capacitors between these pins and GND pins. V IN (Bank 3): Input Power. The VIN pin supplies current to the LTM8055’s internal power switches and to one terminal of the optional input current sense resistor. This pin must be locally bypassed with an external, low ESR capacitor; see Table 1 for recommended values. I OUT (Pin D1): Output Current Sense. Tie this pin to the output current sense resistor. The output average current sense threshold is 58mV, so the LTM8055 will regulate the output current to 58mV/RSENSE, where RSENSE is the value of the output current sense resistor in ohms. The load is powered through the sense resistor connected at this pin. Tie this pin to V OUT if no output current sense resistor is used. Keep this pin within ±0.5V of VOUT under all conditions. LL (Pin F1): Light Load Indicator. This open drain pin indicates that the output current, as sensed through the resistor connected between V OUT and I OUT, is approxi- mately equivalent to 6mV or less. Its state is meaningful only if a current sense resistor is applied between V OUT and IOUT. This is useful to change the switching behavior of the LTM8055 in light load conditions. SVIN (Pins F10, F11): Controller Power Input. Apply a separate voltage above 5V if the LTM8055 is required to operate when the main power input (V IN) is below 5V. Bypass these pins with a high quality, low ESR capacitor. If a separate supply is not used, connect these pins to VIN. CLKOUT (Pin G1): Clock Output. Use this pin as a clock source when synchronizing other devices to the switch - ing frequency of the LTM8055. When this function is not used, leave this pin open. MODE (Pin G2): Switching Mode Input. The LTM8055 oper- ates in forced continuous mode when MODE is open, and can operate in discontinuous switching mode when MODE is low. In discontinuous switching mode, the LTM8055 will block reverse inductor current. This pin is normally left open or tied to LL. This pin may be tied to GND for the purpose of blocking reverse current if no output current sense resistor is used. RT (Pin H1): Timing Resistor. The RT pin is used to program the switching frequency of the LTM8055 by connecting a resistor from this pin to ground. The range of oscillation is 100kHz to 800kHz. The Applications Information section of the data sheet includes a table to determine the resistance value based on the desired switching frequency. Minimize capacitance at this pin. SYNC (Pin H2): External Synchronization Input. The SYNC pin has an internal pull-down resistor. See the Synchroni- zation section in Applications Information for details. Tie this pin to GND when not used. FB (Pin J1): Output Voltage Feedback. The LTM8055 regulates the FB pin to 1.2V. Connect the FB pin to a resistive divider between the output and GND to set the output voltage. See Table 1 for recommended FB divider resistor values. COMP (Pin J2): Compensation Pin. The LTM 8055 is equipped with internal compensation that works well with most applications. In some cases, the performance of the LTM8055 can be enhanced by modifying the control loop compensation by applying a capacitor or RC network to this pin. SS (Pin K1): Soft-Start. Connect a capacitor from this pin to GND to increase the soft-start time. Soft-start reduces the input power source’s surge current by gradually in - creasing the controller’s current limit. Larger values of the soft-start capacitor result in longer soft-start times. If no soft-start is required, leave this pin open. CTL (Pin K2): Current Sense Adjustment. Apply a voltage below 1.2V to reduce the current limit threshold of I OUT. Drive CTL to less than 50mV to stop switching. The CTL pin has an internal pull-up resistor to 2V. If not used, leave open.

8055fb For more information www.linear .com/L TM8055 PIN FUNCTIONS IOUTMON (Pin L2): Output Current Monitor. This pin pro- duces a voltage that is proportional to the voltage between VOUT and IOUT. IOUTMON will equal 1.2V when VOUT – IOUT = 58mV. This feature is generally useful only if a current sense resistor is applied between VOUT and IOUT. This is a high impedance output. Use a buffer to drive a load. IINMON (Pin L3): Input Current Monitor. This pin produces a voltage that is proportional to the voltage between I IN and VIN. IINMON will equal 1V when IIN – VIN = 50mV. This feature is generally useful only if a current sense resistor is applied between VIN and IIN. RUN (Pin L4): LTM8055 Enable. Raise the RUN pin voltage above 1.2V for normal operation. Above 1.2V (typical), but below 6V, the RUN pin input bias current is less than 1μA. Below 1.2V and above 0.3V, the RUN pin sinks 3μA so the user can define the hysteresis with the external resis- tor selection. This will also reset the soft-start function. If RUN is 0.3V or less, the LTM8055 is disabled and the SVIN quiescent current is below 1μA. IIN (Pin L9): Input Current Sense. Tie this pin to the input current sense resistor. The input average current sense threshold is 50mV, so the LTM8055 will regulate the input current to 50mV/RSENSE, where RSENSE is the value of the input current sense resistor in ohms. Tie to VIN when not used. Keep this pin within ±0.5V of VIN under all conditions. BLOCK DIAGRAM 0.2µF 4.7µH 0.47µF 50V 0.1µF CTL COMP RT SYNC 100k 100k IOUTMON 8055 BD IINMON CLKOUT FB IOUT VOUT SS GND RUN IIN VIN SVIN BUCK-BOOST CONTROLLER LLMODE

8055fbFor more information www.linear .com/L TM8055 OPERATION The LTM8055 is a standalone nonisolated buck-boost switching DC/DC power supply. The buck-boost topol- ogy allows the LTM8055 to regulate its output voltage for input voltages both above and below the magnitude of the output. The maximum output current depends upon the input voltage. Higher input voltages yield higher maximum output current. This converter provides a precisely regulated output volt- age programmable via an external resistor divider from 1.2V to 36V. The input voltage range is 5V to 36V, but the LTM8055 may be operated at lower input voltages if SVIN is powered by a voltage source above 5V. A simplified block diagram is given on the previous page. The LTM8055 contains a current mode controller, power switching elements, power inductor and a modest amount of input and output capacitance. The LTM8055 is a fixed frequency PWM regulator. The switching frequency is set by connecting the appropriate resistor value from the RT pin to GND. The output voltage of the LTM8055 is set by connecting the FB pin to a resistor divider between VOUT and GND. In addition to regulating its output voltage, the LTM8055 is equipped with average current control loops for both the input and output. Add a current sense resistor between IIN and VIN to limit the input current below some maximum value. The IINMON pin reflects the current flowing though the sense resistor between IIN and VIN. A current sense resistor between V OUT and I OUT allows the LTM8055 to accurately regulate its output current to a maximum value set by the value of the sense resistor. When the resistor is present, the IOUTMON pin reflects the output current flowing through VOUT. In general, the LTM8055 should be used with an output sense resistor to limit the maximum output current, as buck-boost regulators are capable of delivering large currents when the output voltage is lower than the input, if demanded. Furthermore, while the LTM8055 does not require an output sense resistor to operate, it uses information from the sense resistor to optimize its performance. If an out- put sense resistor is not used, the efficiency or output ripple may degrade, especially if the current through the integrated inductor is discontinuous. In some cases, an output sense resistor is required to adequately protect the LTM8055 against output overload or short-circuit. A voltage less than 1.2V applied to the CTL pin reduces the maximum output current. Drive CTL to about 50mV to stop switching. The current flowing through the sense resistor is reflected by the output voltage of the IOUTMON pin. Driving the SYNC pin will synchronize the LTM8055 to an external clock source. The CLKOUT pin sources a signal that is the same frequency but approximately 180° out of phase with the internal oscillator. If more output current is required than a single LTM8055 can provide, multiple devices may be operated in parallel. Refer to the Parallel Operation section of Applications Information for more details. An internal regulator provides power to the control circuitry and the gate driver to the power MOSFETs. This internal regulator draws power from the SVIN pin. The RUN pin is used to place the LTM8055 in shutdown, disconnecting the output and reducing the input current to less than 1μA. The LTM8055 is equipped with a thermal shutdown that inhibits power switching at high junction temperatures. The activation threshold of this function is above 125°C to avoid interfering with normal operation, so prolonged or repetitive operation under a condition in which the thermal shutdown activates may damage or impair the reliability of the device.

input range and output voltage. Performance Characteristics section for guidance. given input condition is given in the f OPTIMAL column. Synchronization section for details. Table 1. Recommended Component Values and Configuration (TA = 25°C) resistor values for the RFB network are acceptable. Table 2. Electrolytic Caps Used in LTM8055 Testing

load and environmental conditions. ESR. However, not all ceramic capacitors are suitable. inductance forms a high Q (underdamped) tank circuit. avoided; see the Hot-Plugging Safely section. by tying a resistor from the RT pin to ground. Table 3. Switching Frequency vs RT Value LTM8055 if the output is overloaded or short circuited.

LTM8055 output current sense resistor is the same value. slaves in discontinuous mode (MODE = LL) is desirable. a discussion of this behavior. enough current if the input supply voltage is below 8V.

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Figure 2. This Simple Resistor Network Sets the Minimum Figure 1. Tw o or More LTM8055s May Be Connected in a master and slave units, they will share current equally. from the integrated pull-up on the CTL pins.

1. Tie the outputs together.

Characteristics section for guidance. is only if VIN and SVIN are tied to the same voltage source.

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in the Typical Applications section. where RSENSE is the value of the sense resistor in ohms. mance—see Switching Mode in this section. to protect the LTM8055 against these fault conditions. current limit. If this function is not used, leave CTL open. CTL pin has an internal pull-up resistor to 2V. than some predetermined current from the power source. where RSENSE is the value of the sense resistor in ohms. If input current limiting is not required, simply tie IIN to VIN.

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Figure 3. Set The LTM8055 Output Current Limit with an External Figure 4. Set the LTM8055 Input Current Limit with an

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8055fb For more information www.linear .com/L TM8055 Input Current Monitor (IINMON) The IINMON pin produces a voltage equal to approximately 20 times the voltage of IIN – VIN. Since the LTM8055 input current limit engages when IIN – VIN = 50mV, IINMON will be 1V at maximum input current. Output Current Monitor (IOUTMON) The IOUTMON pin produces a voltage proportional to the voltage of VOUT – IOUT. Since the LTM8055 output current limit engages when VOUT – IOUT = 58mV, IOUTMON will be 1.2V at maximum output current. Synchronization The LTM8055 switching frequency can be synchronized to an external clock using the SYNC pin. Driving SYNC with a 50% duty cycle waveform is a good choice, otherwise maintain the duty cycle between about 10% and 90%. When synchronizing, a valid resistor value (that is, a value that results in a free-running frequency of 100kHz to 800kHz) must be connected from RT to GND. While an RT resistor is required for proper operation, the value of this resistor is independent of the frequency of the externally applied SYNC signal. Be aware, however, that the LTM8055 will switch at the frequency prescribed by the RT value if the SYNC signal terminates, so choose an appropriate resistor value. CLKOUT The CLKOUT signal reflects the internal switching clock of t he LTM8055. It is phase shifted by approximately 180° with respect to the leading edge of the internal clock. If CLKOUT is connected to the SYNC input of another LTM8055, the two devices will switch about 180° out of phase. Input Precaution In applications where the output voltage is deliberately pulled up above the set regulation voltage or the FB pin is abruptly driven to a new voltage, the LTM8055 may attempt to regulate the voltage by removing energy from the load for a short period of time after the output is pulled up. Since the LTM8055 is a synchronous switching converter, it delivers this energy to the input. If there is nothing on the LTM8055 input to consume this energy, the input voltage may rise. If the input voltage rises without intervention, it may rise above the absolute maximum rating, damaging the part. Carefully examine the input voltage behavior to see if the application causes it to rise. In many cases, the system load on the LTM8055 input bus will be sufficient to absorb the energy delivered by the μModule regulator. The power required by other devices will consume more than enough to make up for what the LTM8055 delivers. In cases where the LTM8055 is the largest or only power converter, this may not be true and some means may need to be devised to prevent the LTM8055’s input from rising too high. Figure 5a shows a passive crowbar circuit that will dissipate energy during momentary input overvoltage conditions. The break-down voltage of the Zener diode is chosen in conjunction with the resistor R to set the circuit’s trip point. The trip point is typically set well above the maximum VIN voltage under normal operating conditions. This circuit does not have a precision threshold, and is subject to both part-to-part and temperature variations, so it is most suitable for ap- plications where the maximum input voltage is much less than the 40VIN absolute maximum. As stated earlier, this type of circuit is best suited for momentary overvoltages. Figure 5a is a crowbar circuit, which attempts to prevent the input voltage from rising above some level by dumping energy to GND through a power device. In some cases, it is possible to simply turn off the LTM8055 when the input voltage exceeds some threshold. An example of this circuit is shown in Figure 5b. When the power source on the output drives V IN above a predetermined threshold, the comparator pulls down on the RUN pin and stops switching in the LTM8055. When this happens, the input capacitance needs to absorb the energy stored within the LTM8055’s internal inductor, resulting in an additional voltage rise. This voltage rise depends upon the input capacitor size and how much current is flowing from the LTM8055 output to input. APPLICATIONS INFORMATION

8055fbFor more information www.linear .com/L TM8055 Switching Mode The MODE pin allows the user to select either discontinuous mode or forced continuous mode switching operation. In forced continuous mode, the LTM8055 will not skip cycles, even when the internal inductor current falls to zero or even reverses direction. This has the advantage of operating at the same fixed frequency for all load conditions, which can be useful when designing to EMI or output noise speci - fications. Forced continuous mode, however, uses more current at light loads, and allows current to flow from the load back into the input if the output is raised above the regulation point. This reverse current can raise the input voltage and be hazardous if the input is allowed to rise uncontrollably. Please refer to Input Precautions in this section for a discussion of this behavior. Forced continuous operation may provide improved output regulation when the LTM8055 transitions from buck, buck-boost or boost operating modes, especially at lighter loads. In such a case, it can be desirable to oper- ate in forced continuous mode except when the internal inductor current is about to reverse. If so, apply a current sense resistor between VOUT and IOUT and tie the LL and MODE pins together. The LL pin is low when the current through the output sense resistor is about one-tenth the full-scale maximum. When the output current falls to this level, the LL pin will pull the MODE pin down, putting the LTM8055 in discontinuous mode, preventing reverse cur- rent from flowing from the output to the input. In the case where MODE and LL are tied together, a small capacitor (~0.1µF) from these pins to GND may improve the light load transient response by delaying the transition from the discontinuous to forced continuous switching modes. MODE may be tied to GND for the purpose of blocking reverse current if no output current sense resistor is used. FB Resistor Divider and Load Regulation The LTM8055 regulates its FB pin to 1.2V, using a resistor divider to sense the output voltage. The location at which the output voltage is sensed affects the load regulation. If there is a current sense resistor between V OUT and IOUT, and the output is sensed at VOUT, the voltage at the load will drop by the value of the current sense resistor multiplied by the output current. If the output voltage can be sensed at IOUT, the load regulation may be improved. PCB Layout Most of the headaches associated with PCB layout have been alleviated or even eliminated by the high level of integration of the LTM8055. The LTM8055 is neverthe - less a switching power supply, and care must be taken to minimize EMI and ensure proper operation. Even with the high level of integration, you may fail to achieve specified operation with a haphazard or poor layout. See Figure 6 for a suggested layout. Ensure that the grounding and heat sinking are acceptable. A few rules to keep in mind are: Place the RFB and RT resistors as close as possible to their respective pins. APPLICATIONS INFORMATION VIN ZENER DIODE R Q

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10µF L TM8055 LOAD CURRENT GND VOUT SOURCING LOAD EXTERNAL REFERENCE VOL TAGE Figure 5a. The MOSFET Q Dissipates Momentary Energy to GND. The Zener Diode and Resistor Are Chosen to Ensure That the MOSFET Turns On Above the Maximum V IN Voltage Under Normal Operation Figure 5b. This Comparator Circuit Turns Off the LTM8055 if the Input Rises Above a Predetermined Threshold. When the LTM8055 Turns Off, the Energy Stored in the Internal Inductor Will Raise V IN a Small Amount Above the Threshold

1. Place the CIN capacitor as close as possible to the VIN

and GND connection of the LTM8055. VOUT and GND connection of the LTM8055. area of the IIN trace and the trace from VIN to RIN. vias than a board that uses larger holes. Figure 6. Layout Showing Suggested External Components,

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8055fbFor more information www.linear .com/L TM8055 to prevent this overshoot. This can be accomplished by installing a small resistor in series with VIN, but the most popular method of controlling input voltage overshoot is to add an electrolytic bulk capacitor to the V IN net. This capacitor’s relatively high equivalent series resistance damps the circuit and eliminates the voltage overshoot. The extra capacitor improves low frequency ripple filter- ing and can slightly improve the efficiency of the circuit, though it is likely to be the largest component in the circuit. Thermal Considerations The LTM8055 output current may need to be derated if it is required to operate in a high ambient temperature or deliver a large amount of continuous power. The amount of current derating is dependent upon the input voltage, output power and ambient temperature. The temperature rise curves given in the Typical Performance Character - istics section can be used as a guide. These curves were generated by a LTM8055 mounted to a 58cm2 4-layer FR4 printed circuit board. Boards of other sizes and layer count can exhibit different thermal behavior, so it is incumbent upon the user to verify proper operation over the intended system’s line, load and environmental operating conditions. The thermal resistance numbers listed in the Pin Configura- tion of the data sheet are based on modeling the µModule package mounted on a test board specified per JESD 51-9 (Test Boards for Area Array Surface Mount Package Thermal Measurements). The thermal coefficients provided on this page are based on JESD 51-12 (Guidelines for Reporting and Using Electronic Package Thermal Information). For increased accuracy and fidelity to the actual application, many designers use FEA to predict thermal performance. To that end, the Pin Configuration of the data sheet typi- cally gives four thermal coefficients: θ JA – Thermal resistance from junction to ambient. θJCbottom – Thermal resistance from junction to the bottom of the product case. θ JCtop – Thermal resistance from junction to top of the product case. θ JB – Thermal resistance from junction to the printed circuit board. While the meaning of each of these coefficients may seem to be intuitive, JEDEC has defined each to avoid confusion and inconsistency. These definitions are given in JESD 51-12, and are quoted or paraphrased below: θ JA is the natural convection junction-to-ambient air thermal resistance measured in a one cubic foot sealed enclosure. This environment is sometimes referred to as “still air” although natural convection causes the air to move. This value is determined with the part mounted to a JESD 51-9 defined test board, which does not reflect an actual application or viable operating condition. θJCbottom is the thermal resistance between the junction and bottom of the package with all of the component power dissipation flowing through the bottom of the package. In the typical µModule converter, the bulk of the heat flows out the bottom of the package, but there is always heat flow out into the ambient environment. As a result, this thermal resistance value may be useful for comparing packages but the test conditions don’t generally match the user’s application. θJCtop is determined with nearly all of the component power dissipation flowing through the top of the package. As the electrical connections of the typical µModule converter are on the bottom of the package, it is rare for an application to operate such that most of the heat flows from the junc- tion to the top of the part. As in the case of θJCbottom, this value may be useful for comparing packages but the test conditions don’t generally match the user’s application. θ JB is the junction-to-board thermal resistance where almost all of the heat flows through the bottom of the µModule converter and into the board, and is really the sum of the θJCbottom and the thermal resistance of the bottom of the part through the solder joints and through a portion of the board. The board temperature is measured a specified distance from the package, using a 2-sided, 2-layer board. This board is described in JESD 51-9. Given these definitions, it should now be apparent that none of these thermal coefficients reflects an actual physical operating condition of a µModule converter. Thus, none APPLICATIONS INFORMATION

8055fb For more information www.linear .com/L TM8055 APPLICATIONS INFORMATION of them can be individually used to accurately predict the thermal performance of the product. Likewise, it would be inappropriate to attempt to use any one coefficient to correlate to the junction temperature versus load graphs given in the product’s data sheet. The only appropriate way to use the coefficients is when running a detailed thermal analysis, such as FEA, which considers all of the thermal resistances simultaneously. A graphical representation of these thermal resistances is given in Figure 7. The blue resistances are contained within the µModule converter, and the green are outside. The die temperature of the LTM8055 must be lower than the maximum rating of 125°C, so care should be taken in the layout of the circuit to ensure good heat sinking of the LTM8055. The bulk of the heat flow out of the LTM8055 is through the bottom of the μModule converter and the BGA pads into the printed circuit board. Consequently a poor printed circuit board design can cause excessive heating, resulting in impaired performance or reliability. Please refer to the PCB Layout section for printed circuit board design suggestions. Figure 7

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µMODULE CONVERTER JUNCTION-TO-CASE (TOP) RESISTANCE JUNCTION-TO-BOARD RESISTANCE JUNCTION-TO-AMBIENT RESISTANCE (JESD 51-9 DEFINED BOARD) CASE (TOP)-TO-AMBIENT RESISTANCE BOARD-TO-AMBIENT RESISTANCE JUNCTION-TO-CASE (BOTTOM) RESISTANCE JUNCTION AMBIENT CASE (BOTTOM)-TO-BOARD RESISTANCE

8055fbFor more information www.linear .com/L TM8055 TYPICAL APPLICATIONS 12VOUT Fan Power from 3VIN to 36VIN with Analog Current Control and 2A Input Current Limiting Maximum Output Current vs CTL Voltage Output Voltage vs Output Current 24VOUT from 7VIN to 36VIN with 2.1A Accurate Current Limit VIN SVIN IIN GNDMODE LL L TM8055 IOUT 0.027/uni03A9VOUT CLKOUT IINMON IOUTMON FB RUN COMP SS SYNC CTL RT 5.23k

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22µF 25V 33µF 35V V OUT 24V 10µF 50V V IN 7V TO 36V 36.5k fSW = 600kHz 100k CTL VOL TAGE (V) OUTPUT CURRENT (A) 1.2 0.8 0.6 0.4 0.2 1.0

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0.05/uni03A9VOUT CLKOUT IINMON IOUTMON FB RUN COMP SS SYNC CTL RT 0.022/uni03A9 11.0k 100k

8055 TA02a

22µF 25V VOUT 12V MAX FAN 10µF 50V V IN 3V TO 36V 1µF 50V 36.5k fSW = 600kHz 0.2V TO 1.2V CONTROL RANGE DAC 68µF 25V OUTPUT CURRENT (A) OUTPUT VOL TAGE (V)

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1.5 20 0.5 1 2.5 12VIN

8055fb For more information www.linear .com/L TM8055 3.3VOUT from 9VIN to 24VIN with 5A Accurate Current Limit and Output Current Monitor TYPICAL APPLICATIONS Tw o LTM8055s Paralleled to Get More Output Current. The Tw o µModules Are Synchronized and Switching 180° Out Of Phase VIN SVIN IIN GNDMODE LL L TM8055 IOUT 0.011/uni03A9VOUT CLKOUT IINMON IOUTMON FB RUN CTL SS SYNC COMP RT 56.2k 8055 TA04a 22µF 6.3V 100µF 6.3V V OUT 3.3V OUTPUT CURRENT MONITOR 10µF 50V V IN 9V TO 24V 36.5k fSW = 600kHz 100k + OUTPUT CURRENT (A) OUTPUT VOL TAGE (V) 4.0 3.0 2.5 2.0 1.0 0.5 1.5 3.5

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Output Voltage vs Output Current VIN SVIN IIN GNDMODE LL L TM8055 (MASTER) IOUT 0.008/uni03A9VOUT IINMON IOUTMON FB RUN CTL SS SYNC COMP RT CLKOUT 22µF 25V 68µF 25V V OUT 12V 10µF 50V 47pF 47pF VIN 7V TO 36V 36.5k VIN SVIN IIN GND L TM8055 (SLAVE) IOUT 0.008/uni03A9VOUT CTL CLKOUT IINMON IOUTMON FB RUN COMP SS SYNC RT 11k 100k 9.31k

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10µF 50V 36.5k fSW = 600kHz MODE LL 100k 22µF 25V 68µF 25V L T1636 IOUTMON Voltage vs Output Current for Each Channel, 12VIN COMBINED CURRENTS OF BOTH CHANNELS (A) VIOUTMON (V) 1.2 0.8 0.6 0.4 0.2 1.0

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8055fbFor more information www.linear .com/L TM8055 TYPICAL APPLICATIONS Tw o LTM8055s Powered from Different Input Sources to Run a Single Load. Each LTM8055 Draws No More Than 1.8A from Its Respective Power Source, and Are Synchronized 180° Out Of Phase with Each Other Input Current and Output Voltage vs Output Current 12VIN VIN SVIN IIN GNDLL MODE L TM8055 IOUT VOUT IINMON IOUTMON FB RUN CTL SS SYNC COMP RT CLKOUT 22µF 25V 3A MAX VOUT 12V68µF 35V 10µF 50V SUPPL Y 1 6V TO 36V IN SUPPL Y 2 6V TO 36VIN 36.5k VIN0.025/uni03A9 0.025/uni03A9 SVIN IIN GNDLL L TM8055 IOUT VOUT CLKOUT IINMON IOUTMON FB RUN CTL SS SYNC COMP RT 11k

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22µF 25V 10µF 50V 36.5k f SW = 600kHz 47pF 47pF MODE 100k 11k 100k OUTPUT CURRENT (A) INPUT CURRENT (A) VOUT (V) 2.5 1.5 1.0 0.5 2.0

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INPUT CURRENT , REGULATOR 1 INPUT CURRENT , REGULATOR 2

Table 4. LTM8055 Pin Assignment (Arranged by Pin Number)

8055fbFor more information www.linear .com/L TM8055 PACKAGE PHOTO

8055fb For more information www.linear .com/L TM8055 PACKAGE DESCRIPTION Please refer to http://www.linear.com/product/LTM8055#packaging for the most recent package drawings. PACKAGE TOP VIEW PIN “A1” CORNER Y X aaa Z aaa Z DETAIL A PACKAGE BOTTOM VIEW SEE NOTES L K J H G F E D C B A 1 2 38 9 10 11 4 5 6 7 PIN 1 121-Lead (15.00mm × 15.00mm × 4.92mm) (Reference LTC DWG# 05-08-1891 Rev A) NOTES: 1. DIMENSIONING AND TOLERANCING PER ASME Y14.5M-1994 2. ALL DIMENSIONS ARE IN MILLIMETERS BALL DESIGNATION PER JESD MS-028 AND JEP95 5. PRIMARY DATUM -Z- IS SEATING PLANE 6. SOLDER BALL COMPOSITION CAN BE 96.5% Sn/3.0% Ag/0.5% Cu OR Sn Pb EUTECTIC DETAILS OF PIN #1 IDENTIFIER ARE OPTIONAL, BUT MUST BE LOCATED WITHIN THE ZONE INDICATED. THE PIN #1 IDENTIFIER MAY BE EITHER A MOLD OR MARKED FEATURE DETAIL A Øb (121 PLACES) DETAIL B SUBSTRATE A ccc Z DETAIL B PACKAGE SIDE VIEW MOLD CAP Z M X Y Z ddd M Z eee SYMBOL A b D E e F G aaa bbb ccc ddd eee MIN 4.72 0.50 4.22 0.71 0.610 0.27 3.95 NOM 4.92 0.60 4.32 0.78 0.635 15.00 15.00 1.27 12.70 12.70 0.32 4.00 MAX 5.12 0.70 4.42 0.85 0.660 0.37 4.05 0.15 0.10 0.20 0.30 0.15 NOTES DIMENSIONS TOTAL NUMBER OF BALLS: 121 D E e b F G SUGGESTED PCB LAYOUT TOP VIEW 0.000 3.810 5.080 3.810 6.350 5.080 6.350 2.540 1.270 2.540 1.270 6.350 5.080 1.270 6.350 5.080 3.810 2.540 1.270 0.3175 0.3175 3.810 2.540 0.000 // bbb Z Z 0.635 ±0.025 Ø 121x L TMXXXXXX µModule BGA 121 1112 REV A TRAY PIN 1 BEVEL PACKAGE IN TRAY LOADING ORIENTATION COMPONENT PIN “A1”

7 PACKAGE ROW AND COLUMN LABELING MAY VARY

AMONG µModule PRODUCTS. REVIEW EACH PACKAGE LAYOUT CAREFULL Y SEE NOTES

8055fbFor more information www.linear .com/L TM8055 Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.

REVISION HISTORY

REV DATE DESCRIPTION PAGE NUMBER A 01/16 Added Buck-Bost Selection Table 1 B 05/17 Added text to I OUTMON (pin L2) 8

8055fb For more information www.linear .com/L TM8055 DESIGN RESOURCES SUBJECT DESCRIPTION µModule Design and Manufacturing Resources Design:

• Selector Guides
• Demo Boards and Gerber Files
• Free Simulation Tools Manufacturing:
• Quick Start Guide/Demo Manual
• PCB Design, Assembly and Manufacturing Guidelines
• Package and Board Level Reliability µModule Regulator Products Sear ch 1. Sort table of products by parameters and download the result as a spread sheet. 2. Search using the Quick Power Sear ch parametric table. TechClip Videos Quick videos detailing how to bench test electrical and thermal performance of µModule products. Digital Power System Management Linear Technology’s family of digital power supply management ICs are highly integrated solutions that offer essential functions, including power supply monitoring, supervision, margining and sequencing, and feature EEPROM for storing user configurations and fault logging.  LINEAR TECHNOLOGY CORPORATION 2015 LT 0517 REV B • PRINTED IN USA www.linear .com/L TM8055 RELATED PARTS TYPICAL APPLICATION PART NUMBER DESCRIPTION COMMENTS LTM4605 Higher Power Buck-Boost (Up to 60W) External Inductor, Synchronous Switching Buck-Boost; Up to 36V IN, 0.8V ≤ VOUT ≤ 16V LTM4607 Higher Power Buck-Boost (Up to 60W) External Inductor, Synchronous Switching Buck-Boost; Up to 36VIN, 0.8V ≤ VOUT ≤ 24V LTM4609 Higher Power Buck-Boost (Up to 60W) External Inductor, Synchronous Switching Buck-Boost; Up to 36VIN, 0.8V ≤ VOUT ≤ 34V LTM8045 Smaller, Lower Power SEPIC and Inverting; 700mA, 6.25mm × 11.25mm × 4.92mm BGA LTM8046 Isolated, Lower Power Flyback T opology, 550mA (5VOUT, 24VIN), UL60950, 2kVAC 14.4V, 3A Lead-Acid Battery Charger Input Current Limited to 2.1A Input Current vs Input Voltage, IOUT = 3A VIN SVIN IIN GNDLL MODE L TM8055 IOUT 0.02/uni03A9VOUT CLKOUT IINMON IOUTMON FB RUN CTL SS SYNC COMP RT 0.022/uni03A9 9.09k 100k

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22µF 25V 47µF 25V V OUT 14.4V 10µF 50V V IN 3V TO 36V 36.5k 1µF 50V fSW = 600kHz INPUT VOL TAGE (V) INPUT CURRENT (A) 2.5 2.0 1.5 0.5 1.0

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