ACT2102 | DigiCamel IC Datasheet

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ACT2102 ACTIVE-SEMI | Alldatasheet

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PDF pages: 16

Technical content

FEATURES

2A Output Current
Wide 4.5V to 18V Operating Input Range
Synchronous Buck Topology
Integrated 130mΩ Power MOSFET Switches
Output Adjustable from 0.923V to 12V
Up to 96% Efficiency
Stable with Low ESR Ceramic Output Capacitors
Internal Soft Start
1.5mA Low Standby Input Current
High Light Load Efficiency
Cycle-by-Cycle Over Current Limit
Input Under Voltage Lockout
Hiccup Protection at Short Circuit and Over Current
Frequency Fold Back Protection
Low Power Dissipation at Over Current and Short Circuit

APPLICATIONS

LCD-TV
Set-top Box
Distributed Power Systems
Networking Systems GENERAL DESCRIPTION ACT2102 is a monolithic synchronous buck regulator. The device integrates two 130m Ω MOSFETs, and provides 2A of continuous load current over a wide input voltage of 4.5V to 18V. Current mode control provides fast transient response and cycle-by-cycle current limit. Hiccup at short circuit reduces IC temperatures. An internal soft-start prevents inrush current at turn- on, and in shutdown mode t he supply current drops to 10μA. Pulse-skipping mode at light load reduces standby power down to 1.5mA. This device, available in an 8-pin SOP package, provides a very compact solution with minimal external components. ACT2102 18V/2A Step-Down DC/DC Converter Rev 2, 23-May-12 Efficiency vs. Load Current ACT2102-001 Efficiency (%) Load Current (mA) 10 100 1000 10000 100 VOUT = 5V VIN = 7V VIN = 12V VIN = 18V

ORDERING INFORMATION

PART NUMBER OPERATION TEMPERATURE RANGE PACKAGE PINS PACKING ACT2102SH-T -40°C to 85°C SOP-8 8 TAPE & REEL PIN CONFIGURATION PIN DESCRIPTIONS PIN NAME DESCRIPTION 1 HSB High-Side Bias Input. This pin acts as the positive rail for the high-side switch's gate driver. Connect a 10nF or greater capacitor between HSB and SW pins. 2 IN Input Supply. Bypass this pin to GND with a low ESR capacitor. Drive IN with a 4.5V to 18V power source. See Input Capacitor in the Application Information section. 3 SW Switch Output. Connect this pin to the switching end of the external inductor. Note that a capacitor is required from SW to HSB to power the high-side switch. 4 GND Ground. 5 FB Feedback Input. FB senses the output voltage to regulate that voltage. Drive FB with a resistive voltage divider from the output voltage. The feedback threshold is 0.923V. See Setting the Output Voltage. 6 COMP Compensation Node. COMP is used to compensate the regulation control loop. See Compensation Components. 7 EN Enable Input. When higher than 2.5V, this pin turns the IC on. When lower than 2.3V, this pin turns IC off. When left unconnected, EN is pulled up to logic HIGH with a 2µA pull-up current. EN is a digital input that turns the regulator on or off. 8 N/C Not connected.

Rev 2, 23-May-12 Innovative PowerTM - 3 - www.active-semi.com Copyright © 2012 Active-Semi, Inc. ABSOLUTE MAXIMUM RATINGSc PARAMETER VALUE UNIT IN to GND -0.3 to + 20 V SW to GND -1 to VIN + 1 V HSB to GND V SW - 0.3 to VSW + 6 V FB, EN, COMP to GND -0.3 to + 6 V Continuous SW Current Internally limited A Junction to Ambient Thermal Resistance 105 ˚C/W Maximum Power Dissipation 0.76 W Operating Junction Temperature -40 to 150 ˚C Storage Junction -55 to 150 ˚C Lead Temperature (Soldering 10 sec.) 300 ˚C c: Do not exceed these limits to prevent damage to the device. Ex posure to Absolute Maximum Rating conditions for long periods may affect device reliability.

Rev 2, 23-May-12 Innovative PowerTM - 4 - www.active-semi.com Copyright © 2012 Active-Semi, Inc. PARAMETER SYMBOL TEST COND ITIONS MIN TYP MAX UNIT Shutdown Supply Current VEN = 0V 10 20 µA Supply Current (No Switching) VEN = 3V, VFB = 1.2V 0.75 1.1 mA Feedback Voltage V FB 4.75V ≤ VIN ≤ 18V 0.909 0.923 0.937 V Error Amplifier Voltage Gain A EA 400 V/V Error Amplifier Transconductance G EA ΔIC = ±10μA 800 µA/V High-Side Switch On Resistance R DS(ON)1 130 mΩ Low-Side Switch On Resistance R DS(ON)2 130 mΩ Upper Switch Current Limit 50% Duty Cycle 3.5 A COMP to Current Sense G CS 3.5 A/V Oscillation Frequency F sw 280 310 340 kHz Short Circuit Oscillation Frequency 80 kHz Maximum Duty Cycle D MAX 88 % EN Lockout Threshold Voltage 2.4 2.6 2.8 V EN Lockout Hysteresis 75 mV Input Under Voltage Lockout Threshold Input Voltage Rising 4 4.2 4.4 V Internal Soft Startup Time 2 ms Hiccup Frequency at short circuit 26 Hz Under Voltage Threshold 0.74 V Thermal Shutdown Hysteresis Window 30 °C Thermal Shutdown 160 °C Input Voltage 4.5 18 V

ELECTRICAL CHARACTERISTICS

(VIN = 12V, TA = 25°C, unless otherwise specified.)

Rev 2, 23-May-12 Innovative PowerTM - 5 - www.active-semi.com Copyright © 2012 Active-Semi, Inc. FUNCTIONAL BLOCK DIAGRAM FUNCTIONAL DESCRIPTION As seen in Function Block Diagram, the ACT2102 is peak current mode controlled synchr onous Buck converter. The converter operates as follows: A switching cycle starts when the rising edge of the Oscillator clock output ca uses the High-Side Power Switch to turn on and the Low-Side Power Switch to turn off. With the SW side of the inductor now connected to IN, the inductor current ramps up to store energy in the magnetic field. The inductor current level is measured by the Current Sense Amplifier and added to the Oscillator ramp signal. If the resulting summation is higher than the COMP voltage, the output of the PWM Comparator goes high. When this happens or when Oscillator clock output goes low, the High-Side Power Switch turns off and the Low-Side Power Switch turns on. The High-Side Power Switch is driven by logic using HSB as the positive rail. This pin is charged to VSW + 5V when the Low-Side Power Switch turns on. The COMP voltage is the integration of the error between FB input and the internal 0.923V reference. If FB is lower than the reference voltage, COMP tends to go higher to increase current to the output to keep the output voltage regulated. The Oscillator normally switches at 310kHz. Pulse Skipping Mode To decrease the power recycling at very light load, the low-side FET current is sensed to emulate a diode. When the low-side FET current decreases to zero, the FET is turned off to avoid negative inductor current. At no load and very light load, ACT2102 skips pulse automatically and thus achieve very high light load efficiency. With load increasing, ACT2102 goes into Discontinuous Current Mode (DCM) and then Continuous Current Mode (CCM). Soft Startup The ACT2102 builds in internal soft startup function. The internal FB reference voltage rises to steady state of 0.923V in 2ms to avoid inrush input current during startup. Under Voltage Protection (UVP) At output short circuit or over current, the FB voltage is usually pulled low. To protect the IC at over current and short circuit, the ACT2102 builds in Under Voltage Protection (UVP) function. When ACT2102 detects the FB voltage below 80% of the 0.923V reference, it pulls low COMP voltage and discharges internal soft-start capacitor and goes into hiccup mode. The IC restarts in 32ms after going into hiccup mode. If the short circuit or over current is clear, the IC restarts back to normal mode. The UVP is disabled for 6ms starting from startup. If the output is short at startup, the output voltage never rises to nominal voltage. During the 6ms period of time, the out put current is limited by cycle-by-cycle current limit. With 32ms shutdown period, the average inpu t and output current at short circuit is significantly reduced and the IC is more reliable.

Rev 2, 23-May-12 Innovative PowerTM - 6 - www.active-semi.com Copyright © 2012 Active-Semi, Inc. Secondary Over Current Protection (SOCP) In normal operation, ACT2102 high-side FET current is protected by cy cle-by-cycle current limit. In some fault conditions, the input current may run away. SOCP current limit is set 30% higher than cycle-by-cycle current limit, and once SOCP is triggered, ACT2102 goes into hiccup mode and reduce the power dissipation significantly. Enable Pin The ACT2102 has an enable input EN for turning the IC on or off. The EN pin contains a precision 2.5V comparator with 75mV hysteresis and a 1.3 μA pull-up current source. The comparator can be used with a resistor divider from V IN to program a startup voltage higher than the normal UVLO value. If left floating, the EN pin will be pulled up to roughly 5V by the internal 1.3 μA current source. It can be driven from standard logic signals greater than 2.5V, or driven with open-drain logic to provide digital on/off control. Thermal Shutdown The ACT2102 disables switching when its junction temperature exceeds 160°C and resumes when the temperature has dropped by 30°C.

Rev 2, 23-May-12 Innovative PowerTM - 8 - www.active-semi.com Copyright © 2012 Active-Semi, Inc. (6) ESRRIPPLEOUTMAXRIPPLE RKIV = OUT SW IN LCf28 V APPLICATIONS INFORMATION CONT’D External High Voltage Bias Diode It is recommended that an external High Voltage Bias diode be added when the system has a 5V fixed input or the power supply generates a 5V output. This helps improve the efficiency of the regulator. The High Voltage Bias diode can be a low cost one such as IN4148 or BAT54. Figure 2: External High Voltage Bias Diode This diode is also recommended for high duty cycle operation and high output voltage applications. Input Capacitor The input capacitor needs to be carefully selected to maintain sufficiently low ripple at the supply input of the converter. A low ESR capacitor is highly recommended. Since large current flows in and out of this capacitor during switching, its ESR also affects efficiency. The input capacitance needs to be higher than 10µF. The best choice is the ceramic type, however, low ESR tantalum or electrolytic types may also be used provided that the RMS ripple current rating is higher than 50% of the output current. The input capacitor should be placed close to the IN and GND pins of the IC, with the shortest traces possible. In the case of tantalum or electrolytic types, they can be further away if a small parallel 0.1µF ceramic capacitor is placed right next to the IC. Output Capacitor The output capacitor also needs to have low ESR to keep low output voltage ripple. The output ripple voltage is: where IOUTMAX is the maximum output current, KRIPPLE is the ripple factor, R ESR is the ESR of the output capacitor, f SW is the switching frequency, L is the inductor value, and C OUT is the output capacitance. In the case of ceramic output capacitors, RESR is very small and does not contribute to the ripple. Therefore, a lower capacitance value can be used for ceramic type. In the case of tantalum or electrolytic capacitors, the ripple is dominated by RESR multiplied by the ripple current. In that case, the output capacitor is chosen to have sufficiently low ESR. For ceramic output capacitor, typically choose a capacitance of about 22µF. For tantalum or electrolytic capacitors, choose a capacitor with less than 50mΩ ESR. Optional Schottky Diode During the transition between high-side switch and low-side switch, the body diode of the low-side power MOSFET conducts the inductor current. The forward voltage of this body diode is high. An optional Schottky diode may be paralleled between the SW pin and GND pin to improve overall efficiency.

Rev 2, 23-May-12 Innovative PowerTM - 10 - www.active-semi.com Copyright © 2012 Active-Semi, Inc. Figure 4: Typical Application Circuit for 1.8V/2A DC-DC Converter Table 3: BOM List for 1.8V/2A DC-DC Converter ITEM REFERENCE DESCRIPTION MANUFACTURER QTY

1 U1 IC, ACT2102SH, SOP-8 Active-Semi 1

2 C1 Capacitor, Ceramic, 10µF/25V, 1210, SMD Murata, TDK 1

3 C2 Capacitor, Ceramic, 6.8nF/6.3V, 0603, SMD Murata, TDK 1

4 C3 Capacitor, Ceramic, 10nF/25V, 0603, SMD Murata, TDK 1

5 C4,C5 Capacitor, Ceramic, 47µF/10V, 1206, SMD Murata, TDK 2

6 L1 Inductor,10µH, 3A, 20%, SMD Tyco Electronics 1

7 R1 Chip Resistor, 10k Ω, 0603, 1% Murata, TDK 1

8 R2 Chip Resistor, 10.5k Ω, 0603, 1% Murata, TDK 1 9 R3 Chip Resistor, 6.8k Ω, 0603, 5% Murata, TDK 1

Rev 2, 23-May-12 Innovative PowerTM - 11 - www.active-semi.com Copyright © 2012 Active-Semi, Inc. Figure 5: Typical Application Circuit for 5V/2A DC-DC Converter Table 4: BOM List for 5V/2A DC-DC Converter ITEM REFERENCE DESCRIPTION MANUFACTURER QTY

2 C1 Capacitor, Ceramic, 10µF/50V, 1210, SMD Murata, TDK 1

3 C2 Capacitor, Ceramic, 6.8nF/6.3V, 0603, SMD Murata, TDK 1

4 C3 Capacitor, Ceramic, 10nF/50V, 0603, SMD Murata, TDK 1

5 C4,C5 Capacitor, Ceramic, 22µF/10V, 1206, SMD Murata, TDK 2

6 L1 Inductor, 22µH, 3A, 20% Sumida 1

7 D1 Diode, 75V/150mA, LL4148 Good-ARK

8 R1 Chip Resistor, 47k Ω, 0603, 1% Murata, TDK 1

9 R2 Chip Resistor, 10.5k Ω, 0603, 1% Murata, TDK 1 10 R3 Chip Resistor, 8.2k Ω, 0603, 5% Murata, TDK 1

Rev 2, 23-May-12 Innovative PowerTM - 12 - www.active-semi.com Copyright © 2012 Active-Semi, Inc. TYPICAL PERFORMANCE CHARACTERISTICS (L = 22µH, CIN = 100µF, COUT = 330µF, Ta = 25°C, RCOMP = 15k, CCOMP1 = 2.2nF, CCOMP2 = N/C) ACT2102-005 0.94 0.93 0.92 0.91 0.9 0.95 FB Voltage (V) FB Voltage vs. Load Current ACT2102-006 FB Voltage vs. IC Temperature FB Voltage (V) 0.926 0.923 0.92 0.917 0.914 0.911 0.929 0.932 Temperature (°C) 20 40 60 80 100 120 140 160 ACT2102-007 Shutdown Current vs. VIN Current (µA) VIN Voltage (V) 6 8 10 12 14 18 16 20 ACT2102-003 Frequency vs. VIN Frequency (kHz) 375 350 325 300 275 250 225 200 400 ACT2102-004 Frequency vs. FB Voltage Frequency (kHz) 250 200 150 100 300 350 FB Voltage (V) 0 200 400 600 800 1000 Load Current (mA) 0 400 800 1200 1600 2000 VIN Voltage (V) 2 4 6 8 10 14 12 16 20 22 18 ACT2102-002 Efficiency (%) Load Current (mA) 10 100 1000 10000 100 VOUT = 5V VIN = 7V VIN = 12V VIN = 18V Efficiency vs. Load Current

Rev 2, 23-May-12 Innovative PowerTM - 13 - www.active-semi.com Copyright © 2012 Active-Semi, Inc. TYPICAL PERFORMANCE CHARACTERISTICS CONT’D 10mA Load Operation 100mA Load Operation No Load Operation ACT2102-011 ACT2102-012 ACT2102-013 CH1: VRIPPLE, 10mV/div CH2: SW, 5V/div CH3: I L, 200mA/div TIME: 10µs/div CH1: VRIPPLE, 20mV/div CH2: SW, 5V/div CH3: I L, 1A/div TIME: 2µs/div CH1 CH2 CH1 CH2 CH1 CH2 Standby Current vs. VIN ACT2102-008 2.5 1.5 0.5 Standby Current (mA) VIN Voltage (V) 3 5 7 9 11 13 15 17 19 21 ACT2102-009 IIN vs. VIN at Output Dead Short IIN (mA) 140 120 100 VIN (V) 4 6 8 10 12 14 16 18 20 ACT2102-010 Peak Current Limit vs. Duty Cycle Peak Current (A) 3.2 3.0 2.8 2.6 2.4 3.4 3.6 Duty Cycle 20 30 40 50 60 70 80 90 (L = 22µH, CIN = 100µF, COUT = 330µF, Ta = 25°C, RCOMP = 15k, CCOMP1 = 2.2nF, CCOMP2 = N/C) VIN = 12V V0UT = 5V VIN = 12V V0UT = 5V VIN = 12V V0UT = 5V CH3 CH3 CH1: VRIPPLE, 20mV/div CH2: SW, 5V/div CH3: I L, 1A/div TIME: 2µs/div CH3

Rev 2, 23-May-12 Innovative PowerTM - 14 - www.active-semi.com Copyright © 2012 Active-Semi, Inc. 2A Load Operation TYPICAL PERFORMANCE CHARACTERISTICS CONT’D ACT2102-014 ACT2102-015 Load Transient (0A~1A) ACT2102-016 Start Up with VIN (Load 0A) ACT2102-017 Start Up with EN (Load 0A) ACT2102-018 ACT2102-019 CH1 CH2 CH1 CH2 CH1: VOUT, 50mV/div CH2: ILOAD, 500mA/div TIME: 4ms//div Load Transient (1A~2A) CH1 CH2 CH1 CH2 CH1: VIN, 10V/div CH2: VOUT, 5V/div CH3: SW, 10V/div CH4: I L, 2A/div TIME: 2ms/div Start Up with VIN (Load 2A) CH1 CH2 CH1 CH2 (L = 22µH, CIN = 100µF, COUT = 330µF, Ta = 25°C, RCOMP = 15k, CCOMP1 = 2.2nF, CCOMP2 = N/C) VIN = 12V V0UT = 5V VIN = 12V V0UT = 5V VIN = 12V V0UT = 5V VIN = 12V V0UT = 5V VIN = 12V V0UT = 5V VIN = 12V V0UT = 5V CH3 CH1: VRIPPLE, 50mV/div CH2: SW, 5V/div CH3: I L, 1A/div TIME: 2µs/div CH1: VOUT, 50mV/div CH2: ILOAD, 500mA/div TIME: 4ms//div CH3 CH4 CH3 CH4 CH1: V IN, 10V/div CH2: VOUT, 5V/div CH3: SW, 10V/div CH4: I L, 2A/div TIME: 2ms/div CH3 CH4 CH1: EN, 5V/div CH2: VOUT, 5V/div CH3: SW, 10V/div CH4: I L, 2A/div TIME: 2ms/div

Rev 2, 23-May-12 Innovative PowerTM - 15 - www.active-semi.com Copyright © 2012 Active-Semi, Inc. TYPICAL PERFORMANCE CHARACTERISTICS CONT’D ACT2102-020 Start Up with EN (Load 2A) CH1 CH2 ACT2102-021 Short Circuit CH1 CH2 CH1: IOUT, 10A/div CH2: VOUT, 5V/div CH3: SW, 10V/div CH4: I L, 5A/div TIME: 20ms/div (L = 22µH, CIN = 100µF, COUT = 330µF, Ta = 25°C, RCOMP = 15k, CCOMP1 = 2.2nF, CCOMP2 = N/C) VIN = 12V V0UT = 5V VIN = 12V V0UT = 5V ACT2102-022 Short Circuit Recovery CH1 CH2 VIN = 12V V0UT = 5V ACT2102-023 Start Up with Output Dead Short CH1 CH2 VIN = 12V V0UT = 5V CH1: EN, 5V/div CH2: VOUT, 5V/div CH3: SW, 10V/div CH4: I L, 2A/div TIME: 2ms/div CH3 CH4 CH3 CH4 CH1: IOUT, 5A/div CH2: VOUT, 5V/div CH3: SW, 10V/div CH4: I L, 5A/div TIME: 20ms/div CH3 CH4 CH3 CH4 CH1: EN, 5V/div CH2: I OUT, 5A/div CH3: SW, 10V/div CH4: I L, 5A/div TIME: 20ms/div

Rev 2, 23-May-12 Innovative PowerTM - 16 - www.active-semi.com Copyright © 2012 Active-Semi, Inc. PACKAGE OUTLINE SOP-8 PACKAGE OUTLINE AND DIMENSIONS Active-Semi, Inc. reserves the right to modify the circuitry or specifications without notice. User s should evaluate each product to make sure that it is suitable for their applicat ions. Active-Semi products are not intended or authorized for use as critical components in life-support dev ices or systems. Active-Semi, Inc. does not assume any liability arising out of the use of any product or circuit described in this datasheet, nor does it convey any patent license. Active-Semi and its logo are trademarks of Active-Semi, Inc. For more information on this and other products, contact sales@active-semi.com or visit http://www.active-semi.com. is a registered trademark of Active-Semi. A L C E D B e θ SYMBOL DIMENSION IN MILLIMETERS DIMENSION IN INCHES MIN MAX MIN MAX A 1.350 1.750 0.053 0.069 A1 0.100 0.250 0.004 0.010 A2 1.350 1.550 0.053 0.061 B 0.330 0.510 0.013 0.020 C 0.190 0.250 0.007 0.010 D 4.700 5.100 0.185 0.201 E 3.800 4.000 0.150 0.157 E1 5.800 6.300 0.228 0.248 e 1.270 TYP 0.050 TYP L 0.400 1.270 0.016 0.050 θ 0° 8° 0° 8°

Product Information

ACT2102 specifications and overview.

Summary

18V/2A Step-Down DC/DC Converter Rev 2, 23-May-12

Description

18V/2A Step-Down DC/DC Converter Rev 2, 23-May-12

Source title ACT2102 Datasheet(PDF) - Active-Semi, Inc

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