LT3970 LINER | Alldatasheet
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Technical content
LT3970/LT3970-3.3/LT3970-5 3970fa TYPICAL APPLICATION
DESCRIPTION
40V, 350mA Step-Down Regulator with 2.5µA Quiescent Current and Integrated Diodes The L T®3970 is an adjustable frequency monolithic buck switching regulator that accepts a wide input voltage range up to 40V , and consumes only 2.5μA of quiescent current. A high effi ciency switch is included on the die along with the catch diode, boost diode, and the neces- sary oscillator , control and logic circuitry. Low ripple Burst Mode operation maintains high effi ciency at low output currents while keeping the output ripple below 5mV in a typical application. Current mode topology is used for fast transient response and good loop stability. A catch diode current limit provides protection against shorted outputs and overvoltage conditions. An enable pin with accurate threshold is available, producing a low shutdown current of 0.7μA. A power good fl ag signals when V OUT reaches 90% of the programmed output voltage. The L T3970 is available in small 10-pin MSOP and 3mm × 2mm DFN packages. 5V Step-Down Converter
FEATURES
APPLICATIONS
n Low Ripple Burst Mode® Operation 2.5μA I Q at 12VIN to 3.3VOUT Output Ripple < 5mV P-P n Wide Input Voltage Range: 4.2V to 40V Operating n Adjustable Switching Frequency: 200kHz to 2.2MHz n Integrated Boost and Catch Diodes n 350mA Output Current n Fixed Output Voltages: 3.3V , 5V 1.8μA I Q at 12VIN n Accurate 1V Enable Pin Threshold n Low Shutdown Current: I Q = 0.7μA n Internal Sense Limits Catch Diode Current n Power Good Flag n Output Voltage: 1.21V to 25V n Internal Compensation n Small 10-Pin MSOP and (3mm × 2mm) DFN Packages n Automotive Battery Regulation n Power for Portable Products n Industrial Supplies VIN BOOST L T3970 SWEN PG RT 0.22μF 22pF 22μF2.2μF VIN 6V TO 40V VOUT 350mA 316k226k f = 600kHz 22μH BD FB GND OFF ON
3490 TA01a
Effi ciency L, L T , L TC, L TM, Burst Mode, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. LOAD CURRENT (mA) EFFICIENCY (%) POWER LOSS (mW) 0.01 1 10 100
3970 TA01b
0.01 0.1 0.1 VIN = 12V
LT3970/LT3970-3.3/LT3970-5 3970fa FB/V (Note 1) ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE L T3970EDDB#PBF L T3970EDDB#TRPBF LFCZ 10-Lead (3mm × 2mm) Plastic DFN –40°C to 125°C L T3970IDDB#PBF L T3970IDDB#TRPBF LFCZ 10-Lead (3mm × 2mm) Plastic DFN –40°C to 125°C L T3970EMS#PBF L T3970EMS#TRPBF L TFDB 10-Lead Plastic MSOP –40°C to 125°C L T3970IMS#PBF L T3970IMS#TRPBF L TFDB 10-Lead Plastic MSOP –40°C to 125°C L T3970EDDB-3.3#PBF L T3970EDDB-3.3#TRPBF LFQH 10-Lead (3mm × 2mm) Plastic DFN –40°C to 125°C L T3970IDDB-3.3#PBF L T3970IDDB-3.3#TRPBF LFQH 10-Lead (3mm × 2mm) Plastic DFN –40°C to 125°C L T3970EMS-3.3#PBF L T3970EMS-3.3#TRPBF L TFQG 10-Lead Plastic MSOP –40°C to 125°C L T3970IMS-3.3#PBF L T3970IMS-3.3#TRPBF L TFQG 10-Lead Plastic MSOP –40°C to 125°C L T3970HMS-3.3#PBF L T3970HMS-3.3#TRPBF L TFQG 10-Lead Plastic MSOP –40°C to 150°C L T3970EDDB-5#PBF L T3970EDDB-5#TRPBF LFQF 10-Lead (3mm × 2mm) Plastic DFN –40°C to 125°C L T3970IDDB-5#PBF L T3970IDDB-5#TRPBF LFQF 10-Lead (3mm × 2mm) Plastic DFN –40°C to 125°C L T3970EMS-5#PBF L T3970EMS-5#TRPBF L TFQD 10-Lead Plastic MSOP –40°C to 125°C L T3970IMS-5#PBF L T3970IMS-5#TRPBF L TFQD 10-Lead Plastic MSOP –40°C to 125°C L T3970HMS-5#PBF L T3970HMS-5#TRPBF L TFQD 10-Lead Plastic MSOP –40°C to 150°C Consult L TC Marketing for parts specifi ed with wider operating temperature ranges. *The temperature grade is identifi ed by a label on the shipping container . Consult L TC Marketing for information on non-standard lead based fi nish parts. For more information on lead free part marking, go to: http://www.linear .com/leadfree/ For more information on tape and reel specifi cations, go to: http://www.linear .com/tapeandreel/ ABSOLUTE MAXIMUM RATINGS TOP VIEW GND DDB PACKAGE 10-LEAD (3mm × 2mm) PLASTIC DFN *FB/VOUT EN VIN GND GND RT PG BD BOOST SW6 θJA = 76°C/W EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB *FB/V OUT EN VIN GND GND RT PG BD BOOST SW TOP VIEW MS PACKAGE 10-LEAD PLASTIC MSOP θJA = 100°C/W *FB for L T3970, VOUT for L T3970-3.3, L T3970-5. PIN CONFIGURATION Operating Junction Temperature Range (Note 2) Lead Temperature (Soldering, 10 sec)
LT3970/LT3970-3.3/LT3970-5 3970fa ELECTRICAL CHARACTERISTICS The l denotes the specifi cations which apply over the full operating temperature range, otherwise specifi cations are at TA = 25°C. VIN = 12V , VBD = 3.3V unless otherwise noted. (Note 2) PARAMETER CONDITIONS MIN TYP MAX UNITS Minimum Input Voltage l 4 4.2 V Quiescent Current from VIN VEN Low VEN High VEN High, –40°C to 125°C VEN High, –40°C to 150°C l l 0.7 1.7 1.2 2.7 3.5 μA μA μA μA L T3970 Feedback Voltage l 1.195 1.185 1.21 1.21 1.225 1.235 V V L T3970-3.3 Output Voltage –40°C to 125°C –40°C to 150°C l l 3.26 3.234 3.217 3.3 3.3 3.3 3.34 3.366 3.366 V V V L T3970-5 Output Voltage –40°C to 125°C –40°C to 150°C l l 4.94 4.9 4.875 5.06 5.1 5.1 V V V L T3970 FB Pin Bias Current (Note 3) V FB = 1.21V l 0.1 20 nA FB/Output Voltage Line Regulation 4.2V < V IN < 40V 0.0002 0.01 %/V Switching Frequency R T = 41.2k, VIN = 6V RT = 158k, VIN = 6V RT = 768k, VIN = 6V 1.76 640 160 2.25 800 200 2.64 960 240 MHz kHz kHz Switch Current Limit V IN = 5V , VFB = 0V 535 700 865 mA Catch Schottky Current Limit V IN = 5V 350 400 500 mA Switch VCESAT ISW = 200mA 175 mV Switch Leakage Current 0.05 2 μA Catch Schottky Forward Voltage I SCH = 100mA, VIN = VBD = NC 650 mV Catch Schottky Reverse Leakage V SW = 12V 0.05 2 μA Boost Schottky Forward Voltage I SCH = 50mA, VIN = NC, VBOOST = 0V 875 mV Boost Schottky Reverse Leakage V REVERSE = 12V 0.02 2 μA Minimum Boost Voltage (Note 4) V IN = 5V l 1.4 1.8 V BOOST Pin Current I SW = 200mA, VBOOST = 15V 7 10 mA EN Pin Current V EN = 12V 1 30 nA L T3970 EN Voltage Threshold EN Rising, V IN ≥ 4.2V l 0.94 1 1.06 V L T3970-X EN Voltage Threshold EN Rising, V IN ≥ 4.2V l 0.93 1 1.07 V EN Voltage Hysteresis 30 mV L T3970 PG Threshold Offset from Feedback Voltage V FB Rising 80 120 160 mV L T3970 PG Hysteresis 12 mV L T3970-X PG Threshold Offset from Output Voltage V FB Rising 6.5 10 13.5 % L T3970-X PG Hysteresis as % of Output Voltage 1.0 % PG Leakage V PG = 3V 0.01 1 μA PG Sink Current V PG = 0.4V l 30 80 μA Minimum Switch On-Time 90 ns Minimum Switch Off-Time V IN = 10V l 100 160 ns
LT3970/LT3970-3.3/LT3970-5 3970fa TYPICAL PERFORMANCE CHARACTERISTICS No-Load Supply Current Effi ciency, VOUT = 3.3V Effi ciency, V OUT = 5V L T3970 Feedback Voltage TA = 25°C, unless otherwise noted. LOAD CURRENT (mA) EFFICIENCY (%) 0.01 1 10 100
3970 G01
0.1 VIN = 12V FRONT PAGE APPLICATION VOUT = 3.3V R1 = 1M R2 = 576k VIN = 36V VIN = 24V LOAD CURRENT (mA) EFFICIENCY (%) 0.01 1 10 100
3970 G02
0.1 VIN = 12V FRONT PAGE APPLICATION VIN = 36V VIN = 24V TEMPERATURE (°C) –50 FEEDBACK VOLTAGE (V) 1.210 1.215 1.220 25 75 150
3970 G03
1.205 1.200 1.195 –25 0 50 100 125 INPUT VOLTAGE (V) SUPPLY CURRENT (µA) 1.5 2.0 2.5 3.0 10 20 30 40
3970 G04
3.5 4.0 51 5 25 35 FRONT PAGE APPLICATION VOUT = 3.3V R1 = 1MΩ R2 = 576k L T3970-5 L T3970-3.3
ELECTRICAL CHARACTERISTICS
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 L T3970E is guaranteed to meet performance specifi cations from 0°C to 125°C junction temperature. Specifi cations over the –40°C to 125°C operating junction temperature range are assured by design, characterization, and correlation with statistical process controls. The L T3970I is guaranteed over the full –40°C to 125°C operating junction temperature range. The L T3970H is guaranteed over the full –40°C to 150°C operating junction temperature range. High junction temperatures degrade operating lifetimes. Operating lifetime is derated at junction temperatures greater than 125°C. Note 3: Bias current fl ows into the FB pin. Note 4: This is the minimum voltage across the boost capacitor needed to guarantee full saturation of the switch. TEMPERATURE (°C) –50 OUTPUT VOLTAGE (V) 3.30 3.31 3.32 25 75 150
3970 G03a
3.29 3.28 3.27 –25 0 50 100 125 TEMPERATURE (°C) –50 OUTPUT VOLTAGE (V) 5.00 5.02 5.04 25 75 150
3970 G03b
4.98 4.96 4.94 –25 0 50 100 125 L T3970-5 Output VoltageL T3970-3.3 Output Voltage
LT3970/LT3970-3.3/LT3970-5 3970fa No-Load Supply Current Maximum Load Current Maximum Load Current Maximum Load Current Load Regulation TYPICAL PERFORMANCE CHARACTERISTICS Minimum Switch On-Time/Switch Off-Time Switch Current Limit Switch Current Limit Switching Frequency TA = 25°C, unless otherwise noted. TEMPERATURE (°C) –50 SUPPLY CURRENT (μA) 25 75 150
3970 G05
–25 0 50 100 125 FRONT PAGE APPLICATION VIN = 12V VOUT = 3.3V R1 = 1M R2 = 576k INPUT VOL TAGE (V)
350 LOAD CURRENT (mA)400
3870 G06
VOUT = 3.3V TYPICAL MINIMUM INPUT VOL TAGE (V)
350 LOAD CURRENT (mA)
3870 G07
VOUT = 5V TYPICAL MINIMUM TEMPERATURE (°C) –50 LOAD CURRENT (mA) 300 400 500 600 25 75
3970 G08
–25 0 50 100 150125 LIMITED BY MAXIMUM JUNCTION TEMPERATURE; θ JA = 76°C/W FRONT PAGE APPLICATION V IN = 12V VOUT = 5V LIMITED BY CURRENT LIMIT H GRADE LOAD CURRENT (mA) LOAD REGULATION (%) 0.15 150
3970 G09
–0.10 50 100 200 –0.15 –0.20 0.20 0.10 0.05 –0.05 250 300 350 FRONT PAGE APPLICATION REFERENCED FROM VOUT AT 100mA LOAD DUTY CYCLE (%)
200 SWITCH CURRENT LIMIT (mA)300
3970 G10
CATCH DIODE VALLEY CURRENT LIMIT TEMPERATURE (oC) –50
3970 G11
–25 25 75 125 SWITCH PEAK CURRENT LIMIT CATCH DIODE VALLEY CURRENT LIMIT TEMPERATURE (°C) –50 FREQUENCY (MHz) 0.4 0.8 1.2 1.6 2.4 –25 0 2 55 07 5
3970 G12
2.0 0.2 0.6 1.0 1.4 2.2 1.8 TEMPERATURE (°C) –50 SWITCH ON-TIME/SWITCH OFF-TIME (ns)20 100 200 140 0 50 75
3970 G13
–25 25 100 125 150 MINIMUM OFF-TIME LOAD CURRENT = 175mA MINIMUM ON-TIME
LT3970/LT3970-3.3/LT3970-5 3970fa TYPICAL PERFORMANCE CHARACTERISTICS Power Good Threshold Boost Diode Forward Voltage Catch Diode Forward Voltage Catch Diode Leakage TA = 25°C, unless otherwise noted. BOOST DIODE CURRENT (mA) BOOST DIODE VF (V) 0.2 0.4 0.6 0.8 1.0 1.2 50 100 150 200
3970 G19
–50°C 25°C 125°C 150°C CATCH DIODE CURRENT (mA) CATCH DIODE VF (V) 0.6 0.8 1.0 400
3970 G20
0.4 0.2 100 200 300 –50°C 25°C 125°C 150°C TEMPERATURE (°C) –50 CATCH DIODE LEAKAGE (μA) 25 75 150
3970 G21
–25 0 50 100 125 VR = 12V TEMPERATURE (°C) –50 THRESHOLD (%) –25 0 25 50
3970 G22
Minimum Input Voltage, VOUT = 3.3V Minimum Input Voltage, VOUT = 5V SWITCH CURRENT (mA) 400
3970 G16
BOOST PIN CURRENT (mA) LOAD CURRENT (mA) 05 0 2.5 INPUT VOLTAGE (V) 3.5 5.0 100 200 250
3970 G17
3.0 4.5 4.0 150 300 350 FRONT PAGE APPLICATION VOUT = 3.3V TO START/RUN LOAD CURRENT (mA) 05 0 4.0 INPUT VOLTAGE (V) 5.0 6.5 100 200 250
3970 G18
4.5 6.0 5.5 150 300 350 FRONT PAGE APPLICATION VOUT = 5V TO START TO RUN Switch VCESAT (ISW = 200mA) vs Temperature Switch V CESAT TEMPERATURE (°C) –50
100 SWITCH VCESAT (mV)
–25 0 25 50
3970 G14
SWITCH CURRENT (mA) SWITCH VCESAT (mV) 300 400 400
3970 G15
LT3970/LT3970-3.3/LT3970-5 3970fa EN Threshold T ransient Load Response; Load Current is Stepped from 100mA to 200mA Switching Waveforms, Burst Mode Operation TEMPERATURE (°C) –50 0.950 THRESHOLD VOLTAGE (V)0.975 1.000 1.025 1.050 –25 0 25 50
3970 G23
T ransient Load Response; Load Current is Stepped from 10mA (Burst Mode Operation) to 110mA VOUT 100mV/DIV IL 100mA/DIV 100μs/DIV FRONT PAGE APPLICATION VIN = 12V VOUT = 5V
3970 G24
100μs/DIV FRONT PAGE APPLICATION VIN = 12V VOUT = 5V
3970 G25
Switching Waveforms, Full Frequency Continuous Operation VOUT 5mV/DIV VSW 5V/DIV IL 100mA/DIV 2μs/DIV FRONT PAGE APPLICATION VIN = 12V VOUT = 5V ILOAD = 10mA
3970 G26
1μs/DIV FRONT PAGE APPLICATION VIN = 12V VOUT = 5V ILOAD = 350mA
3970 G27
TYPICAL PERFORMANCE CHARACTERISTICSTA = 25°C, unless otherwise noted.
LT3970/LT3970-3.3/LT3970-5 3970fa PIN FUNCTIONS FB (Pin 1, L T3970 Only): The L T3970 Regulates the FB Pin to 1.21V . Connect the feedback resistor divider tap to this pin. V OUT (Pin 1, L T3970-3.3 and L T3970-5 Only): The L T3970- 3.3 and L T3970-5 regulate the VOUT Pin to 3.3V and 5V respectively. This pin connects to the internal feedback divider that programs the fi xed output voltage. EN (Pin 2): The part is in shutdown when this pin is low and active when this pin is high. The hysteretic threshold voltage is 1V going up and 0.97V going down. Tie to V IN if shutdown feature is not used. The EN threshold is ac- curate only when V IN is above 4.2V . If VIN is lower than 4.2V , ground EN to place the part in shutdown. VIN (Pin 3): The VIN pin supplies current to the L T3970’s internal circuitry and to the internal power switch. This pin must be locally bypassed. GND (Pins 4, 5, Exposed Pad (Pin 11, DFN Only)): Ground. Must be soldered to PCB. SW (Pin 6): The SW pin is the output of an internal power switch. Connect this pin to the inductor . BOOST (Pin 7): This pin is used to provide a drive volt- age, higher than the input voltage, to the internal bipolar NPN power switch. BD (Pin 8): This pin connects to the anode of the boost diode. This pin also supplies current to the L T3970’s internal regulator when BD is above 3.2V . PG (Pin 9): The PG pin is the open-drain output of an internal comparator . PG remains low until the FB pin is within 10% of the fi nal regulation voltage. PG is valid when V IN is above 4.2V and EN is high. RT (Pin 10): A resistor is tied between RT and ground to set the switching frequency. R SWITCH LATCH DBOOST DCATCH BOOST OSCILLATOR 200kHz TO 2.2MHz SLOPE COMP S Q Burst Mode DETECT ERROR AMP 1.09V SHDNEN VIN INTERNAL 1.21V REF RT RT PG FB L T3970 ONL Y *L T3970-3.3: R1 = 12.65M, R2 = 7.35M L T3970-5: R1 = 15.15M, R2 = 4.85M R2 R1 R2 R1 VC GND (4, 5) VIN3 BD 8 SW VOUT6 3990 BD VOUT L T3970-3.3 L T3970-5 ONL Y* BLOCK DIAGRAM
LT3970/LT3970-3.3/LT3970-5 3970fa OPERATION The L T3970 is a constant frequency, current mode step- down regulator . An oscillator , with frequency set by RT, sets an RS fl ip-fl op, turning on the internal power switch. An amplifi er and comparator monitor the current fl owing between the V IN and SW pins, turning the switch off when this current reaches a level determined by the voltage at V C (see Block Diagram). An error amplifi er measures the output voltage through an external resistor divider tied to the FB pin and servos the V C node. If the error amplifi er’s output increases, more current is delivered to the output; if it decreases, less current is delivered. Another comparator monitors the current fl owing through the catch diode and reduces the operating frequency when the current exceeds the 400mA bottom current limit. This foldback in frequency helps to control the output current in fault conditions such as a shorted output with high input voltage. Maximum deliverable current to the output is therefore limited by both switch current limit and catch diode current limit. An internal regulator provides power to the control cir- cuitry. The bias regulator normally draws power from the V IN pin, but if the BD pin is connected to an external voltage higher than 3.2V , bias power will be drawn from the external source (typically the regulated output voltage). This improves effi ciency. If the EN pin is low, the L T3970 is shut down and draws 0.7μA from the input. When the EN pin exceeds 1V , the switching regulator will become active. The switch driver operates from either V IN or from the BOOST pin. An external capacitor is used to generate a voltage at the BOOST pin that is higher than the input supply. This allows the driver to fully saturate the internal bipolar NPN power switch for effi cient operation. To further optimize effi ciency, the L T3970 automatically switches to Burst Mode operation in light load situations. Between bursts, all circuitry associated with controlling the output switch is shut down reducing the input supply current to 1.7μA. The L T3970 contains a power good comparator which trips when the FB pin is at 90% of its regulated value. The PG output is an open-drain transistor that is off when the output is in regulation, allowing an external resistor to pull the PG pin high. Power good is valid when the L T3970 is enabled and V IN is above 4.2V .
current of the application circuit. Table 1. Switching Frequency vs RT Value and VSW is the internal switch drop (~0.5V at max load). the inductor and capacitor values small. maximum duty cycle (as explained in previous section). switching frequency should be used.
where tON(MIN) is the minimum switch on-time (~150ns). however the output will still be in regulation. and switching frequency will determine the ripple current. and its saturation current should be about 30% higher . which is acceptable but reduces maximum load current. subharmonic oscillations. See Application Note 19. Table 2. Inductor Vendors
(see the Hot Plugging Safely section). provide low output ripple and good transient response. cost but transient performance will suffer . should be used with a large output capacitor.
3970 F01
operating conditions (applied voltage and temperature). Table 3. Recommended Ceramic Capacitor Vendors when used with the L T3970 due to their piezoelectric nature. Figure 1. Worst-Case Output Ripple Across Full Load Range
operation, the noise is typically very quiet to a casual ear . or electrolytic capacitor at the output. is easily avoided (see the Hot Plugging Safely section). 5mV for a typical application. See Figure 2. reduced resulting in high effi ciency even at very low loads. 2.2V and above, the standard circuit (Figure 4a) is best. pin quiescent current come from a lower voltage source. BOOST and BD pins are not exceeded. age is also limited by the boost circuit for proper start-up. Figure 2. Burst Mode Operation Figure 3. Switching Frequency in Burst Mode Operation
3970 F02
3070 F03
tie EN pin to GND to place the part in shutdown. Figure 4. T wo Circuits for Generating the Boost Voltage Figure 5. The Minimum Input Voltage Depends on
3970 F04
3970 F05
a L T3970 buck regulator will tolerate a shorted output. Figure 8. Diode D4 Prevents a Shorted Input from Discharging a
3970 F07
Figure 7. VIN Start-Up of Front Page Application with VOUT = 3.3V , No-Load Current, and VIN(EN) programmed as in Figure 6.
3970 F08
Figure 6. Enable
3970 F06
a local, unbroken ground plane below these components. The SW and BOOST nodes should be as small as possible. board and on the bottom side. Figure 9. A Good PCB Layout Ensures Proper , Low EMI Operation by the thermal resistance from junction to ambient. quiescent current of the L T3970 converter .
3970 F09
LT3970/LT3970-3.3/LT3970-5 3970fa TYPICAL APPLICATIONS 3.3V Step-Down Converter VIN BOOST L T3970 SWEN PG RT 0.22μF 22pF 22μF 2.2μF VIN 4.2V TO 40V VOUT 3.3V 350mA 576k226k f = 600kHz 22μH BD FB GND OFF ON
3490 TA02
2.5V Step-Down Converter VIN BOOST L T3970 SWEN PG RT 0.22μF 22pF 226k f = 600kHz 22μF 2.2μF VIN 6V TO 40V VOUT 350mA 316k 22μH BD FB GND OFF ON
3490 TA03
0.47μF 47pF 226k f = 600kHz 47μF 2.2μF VIN 4.2V TO 40V VOUT 2.5V 350mA 931k 15μH BD FB GND OFF ON
3490 TA04
1.8V Step-Down Converter VIN BOOST L T3970 SWEN BD PG RT 0.22μF 47pF 226k f = 600kHz 47μF 2.2μF VIN 4.2V TO 27V VOUT 1.8V 350mA 487k 10μH FB GND OFF ON
3490 TA05
3.3V Step-Down Converter 5V Step-Down Converter VIN BOOST L T3970-3.3 SWEN PG RT 0.22μF 226k f = 600kHz 22μF2.2μF VIN 4.2V TO 40V VOUT 3.3V 350mA 22μH BD VOUT GND OFF ON
3490 TA03a
0.22μF 226k f = 600kHz 22μF2.2μF VIN 6V TO 40V VOUT 350mA 22μH BD VOUT GND OFF ON
3490 TA03b
LT3970/LT3970-3.3/LT3970-5 3970fa TYPICAL APPLICATIONS 12V Step-Down Converter 5V , 2MHz Step-Down Converter VIN BOOST L T3970 SWEN PG RT 0.1μF 22pF 226k f = 600kHz 22μF 2.2μF VIN 14V TO 40V VOUT 12V 350mA 113k 33μH BD FB GND OFF ON
3490 TA06
49.9k f = 2MHz 0.1μF 22pF 10μF 1μF VIN 8.5V TO 16V TRANSIENTS TO 40V VOUT 350mA 316k 10μH BD FB GND OFF ON
3490 TA07
5V Step-Down Converter with Reduced Input Current During Start-Up VIN BOOST L T3970 SWEN PG RT 0.22μF 22pF 22μF2.2μF VIN 6V TO 40V VOUT 350mA 316k226k kΩ f = 600kHz 22μH BD FB GND
3490 TA08a
Input Current During Start-Up INPUT VOLTAGE (V) –0.5 INPUT CURRENT (mA) 0.5 1.5 2.5 2 4 68
3970 TA08b
3.5 4.5 1.0 2.0 3.0 4.0 INPUT CURRENT DROPOUT CONDITIONS FRONT PAGE APPLICATION FRONT PAGE APPLICATION WITH EN PROGRAMMED TO 6V Start-Up from High Impedance Input Source VOUT 2V/DIV VIN 5V/DIV 5ms/DIV FRONT PAGE APPLICATION VOUT = 5V 1k INPUT SOURCE RESISTANCE 2.5mA LOAD
3970 TA08c
LT3970/LT3970-3.3/LT3970-5 3970fa PACKAGE DESCRIPTION 10-Lead Plastic DFN (3mm × 2mm) (Reference L TC DWG # 05-08-1722 Rev Ø) 2.00 ±0.10 (2 SIDES) NOTE: 1. DRAWING CONFORMS TO VERSION (WECD-1) IN JEDEC PACKAGE OUTLINE M0-229 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE 0.40 ± 0.10 BOTTOM VIEW—EXPOSED PAD 0.64 ± 0.05 (2 SIDES) 0.75 ±0.05 R = 0.115 TYPR = 0.05 TYP 2.39 ±0.05 (2 SIDES) 3.00 ±0.10 (2 SIDES) 106 PIN 1 BAR TOP MARK (SEE NOTE 6)
0.200 REF
0 – 0.05 (DDB10) DFN 0905 REV Ø 0.25 ± 0.05 2.39 ±0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 0.64 ±0.05 (2 SIDES) 1.15 ±0.05 0.70 ±0.05 2.55 ±0.05 PACKAGE OUTLINE 0.25 ± 0.05
0.50 BSC
R = 0.20 OR 0.25 s 45° CHAMFER
LT3970/LT3970-3.3/LT3970-5 3970fa PACKAGE DESCRIPTION MSOP (MS) 0307 REV E 0.53 p 0.152 (.021 p .006) SEATING PLANE 0.18 (.007) 1.10 (.043) MAX 0.17 – 0.27 (.007 – .011) TYP 0.86 (.034) REF 0.50 (.0197) BSC 12 3 45 4.90 p 0.152 (.193 p .006) 0.497 p 0.076 (.0196 p .003) REF8910 7 6 3.00 p 0.102 (.118 p .004) (NOTE 3) 3.00 p 0.102 (.118 p .004) (NOTE 4) NOTE: 1. DIMENSIONS IN MILLIMETER/(INCH) 2. DRAWING NOT TO SCALE 3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX 0.254 (.010) 0o – 6o TYP DETAIL “A” DETAIL “A” GAUGE PLANE 5.23 (.206) MIN 3.20 – 3.45 (.126 – .136) 0.889 p 0.127 (.035 p .005) RECOMMENDED SOLDER PAD LAYOUT 0.305 p 0.038 (.0120 p .0015) TYP 0.50 (.0197) BSC 0.1016 p 0.0508 (.004 p .002) 10-Lead Plastic MSOP (Reference L TC DWG # 05-08-1661 Rev E)
LT3970/LT3970-3.3/LT3970-5 3970fa 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 5/10 Added L T3970-3.3 and L T3970-5 1 - 22
LT3970/LT3970-3.3/LT3970-5 3970fa Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear .com © LINEAR TECHNOLOGY CORPORATION 2009 LT 0510 REV A • PRINTED IN USA RELATED PARTS PART NUMBER DESCRIPTION COMMENTS L T3971 38V , 1.2A (I OUT), IQ = 2.8μA High Effi ciency Step-Down DC/DC Converter VIN: 4.3V to 38V , VOUT(MIN) = 1.2V , IQ = 2.8μA, ISD < 1μA, MSOP-10E, 3mm × 3mm DFN-10 L T3991 55V , 1.2A (I OUT), IQ = 2.8μA High Effi ciency Step-Down DC/DC Converter VIN: 4.3V to 55V , VOUT(MIN) = 1.2V , IQ = 2.8μA, ISD < 1μA, MSOP-10E, 3mm × 3mm DFN-10 L T3689 36V , 60V T ransient Protection, 800mA, 2.2MHz High Effi ciency Micropower Step-Down DC/DC Converter with POR Reset and Watchdog Timer V IN: 3.6V to 36V , T ransient to 60V , VOUT(MIN) = 0.8V , IQ = 75μA, ISD < 1μA, 3mm × 3mm QFN-16 L T3682 36V , 60V MAX, 1A, 2.2MHz High Effi ciency Micropower Step-Down DC/DC Converter VIN: 3.6V to 36V , VOUT(MIN) = 0.8V , IQ = 75μA, ISD < 1μA, 3mm × 3mm DFN-12 L T3480 36V with T ransient Protection to 60V , 2A (I OUT), 2.4MHz, High Effi ciency Step-Down DC/DC Converter with Burst Mode Operation VIN: 3.6V to 38V , VOUT(MIN) = 0.78V , IQ = 70μA, ISD < 1μA, 3mm × 3mm DFN-10, MSOP-10E L T3685 36V with T ransient Protection to 60V , 2A (I OUT), 2.4MHz, High Effi ciency Step-Down DC/DC Converter VIN: 3.6V to 38V , VOUT(MIN) = 0.78V , IQ = 70μA, ISD < 1μA, 3mm × 3mm DFN-10, MSOP-10E L T3481 34V with T ransient Protection to 36V , 2A (I OUT), 2.8MHz, High Effi ciency Step-Down DC/DC Converter with Burst Mode Operation VIN: 3.6V to 34V , VOUT(MIN) = 1.26V , IQ = 50μA, ISD < 1μA, 3mm × 3mm DFN-10, MSOP-10E L T1976/L T1977 60V , 1.2A (I OUT), 200/500kHz, High Effi ciency Step-Down DC/DC Converter with Burst Mode Operation VIN: 3.3V to 60V , VOUT(MIN) = 1.20V , IQ = 100μA, ISD < 1μA, TSSOP-16E