LT3470

LT3470 LINEAR | Alldatasheet

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■ Automotive Battery Regulation ■ Power for Portable Products ■ Distributed Supply Regulation ■ Industrial Supplies ■ Wall Transformer Regulation Micropower Buck Regulator with Integrated Boost and Catch Diodes ■ Low Quiescent Current: 26µA at 12VIN to 3.3VOUT ■ Integrated Boost and Catch Diodes ■ Input Range: 4V to 40V ■ Low Output Ripple: <10mV ■ <1µA in Shutdown Mode ■ Output Voltage: 1.25V to 16V ■ 200mA Output Current ■ Hysteretic Mode Control – Low Ripple Burst Mode Operation at Light Loads – Continuous Operation at Higher Loads ■ Solution Size as Small as 50mm2 ■ Low Profile (1mm) ThinSOT Package Efficiency and Power Loss vs Load Current Burst Mode is a registered trademark of Linear Technology Corporation. ThinSOT is a trademark of Linear Technology Corporation. FEATURES DESCRIPTIO U APPLICATIO SU TYPICAL APPLICATIO U The LT 3470 is a micropower step-down DC/DC converter that integrates a 300mA power switch, catch diode and boost diode into a low profile (1mm) ThinSOT TM package. The LT3470 combines Burst Mode and continuous opera- tion to allow the use of tiny inductor and capacitors while providing a low ripple output to loads of up to 200mA. With its wide input range of 4V to 40V, the LT3470 can regulate a wide variety of power sources, from 2-cell Li-Ion batteries to unregulated wall transformers and lead- acid batteries. Quiescent current in regulation is just 26µA in a typical application while a zero current shutdown mode disconnects the load from the input source, simpli- fying power management in battery-powered systems. Fast current limiting and hysteretic control protects the LT3470 and external components against shorted out- puts, even at 40V input. LOAD CURRENT (mA) EFFICIENCY (%) POWER LOSS (mW) 0.1 10 100

3470 TA02

0.1 VIN = 12V VIN BOOST LT3470 SWSHDN 0.22µF 22pF 22µF2.2µF VIN 7V TO 40V VOUT 200mA 604k 200k 33µH BIAS FB GND OFF ON , LTC and LT are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.

(Note 1) IN Operating Temperature Range (Note 2) .. – 40°C to 85°C Consult LTC Marketing for parts specified with wider operating temperature ranges. ABSOLUTE AXI U RATI GSW WW U PACKAGE/ORDER I FOR ATIOUU W SHDN 1 NC 2 VIN 3 GND 4 8 FB

7 BIAS

6 BOOST

TJMAX = 125°C, θJA = 140°C/ W LT3470ETS8 LT3470ITS8 LTBDM LTBPW PARAMETER CONDITIONS MIN TYP MAX UNITS Minimum Input Voltage ● 4V Quiescent Current from VIN VSHDN = 0.2V 0.1 0.5 µA VBIAS = 3V, Not Switching ● 10 18 µA VBIAS = 0V, Not Switching 35 50 µA Quiescent Current from Bias V SHDN = 0.2V 0.1 0.5 µA VBIAS = 3V, Not Switching ● 25 60 µA VBIAS = 0V, Not Switching 0.1 1.5 µA FB Comparator Trip Voltage V FB Falling ● 1.228 1.250 1.265 V FB Pin Bias Current (Note 3) V FB = 1V 35 80 nA

• 35 150 nA FB Voltage Line Regulation 4V < V IN < 40V 0.0006 0.01 %/V Minimum Switch Off-Time (Note 5) 500 ns Switch Leakage Current 0.7 1.5 µA Switch VCESAT ISW = 100mA 215 300 mV Switch Top Current Limit V FB = 0V 250 325 435 mA Switch Bottom Current Limit V FB = 0V 225 mA The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C. VIN = 10V, VSHDN = 10V, VBOOST = 15V, VBIAS = 3V unless otherwise specified.

ELECTRICAL CHARACTERISTICS

Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: The LT3470E is guaranteed to meet performance specifications from 0°C to 70°C. Specifications over the –40°C to 85°C operating temperature range are assured by design, characterization and correlation with statistical process controls. The LT3470I specifications are guaranteed over the –40°C to 125°C temperature range. PARAMETER CONDITIONS MIN TYP MAX UNITS Catch Schottky Drop I SH = 100mA 630 775 mV Catch Schottky Reverse Leakage V SW = 10V 0.2 2 µA Boost Schottky Drop I SH = 30mA 650 775 mV Boost Schottky Reverse Leakage V SW = 10V, VBIAS = 0V 0.2 2 µA Minimum Boost Voltage (Note 4) ● 1.7 2.2 V BOOST Pin Current I SW = 100mA 7 12 mA SHDN Pin Current V SHDN = 2.5V 1 5 µA SHDN Input Voltage High 2.5 V SHDN Input Voltage Low 0.2 V The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C. VIN = 10V, VSHDN = 10V, VBOOST = 15V, VBIAS = 3V unless otherwise specified. Note 3: Bias current flows out of the FB pin. Note 4: This is the minimum voltage across the boost capacitor needed to guarantee full saturation of the switch. Note 5: This parameter is assured by design and correlation with statistical process controls. TYPICAL PERFOR A CE CHARACTERISTICS UW Efficiency, VOUT = 5VEfficiency, VOUT = 3.3V V FB vs Temperature LOAD CURRENT (mA) EFFICIENCY (%) 0.1 10 100

3470 G01

L = TOKO D52LC 47µH TA = 25°C VIN = 7VVIN = 12V VIN = 36VVIN = 24V LOAD CURRENT (mA) EFFICIENCY (%) 0.1 10 100

3470 G02

L = TOKO D52LC 47µH TA = 25°C VIN = 12V VIN = 36VVIN = 24V TEMPERATURE (°C) –50

1.240 VFB (V)

1.245 1.250 1.255 1.260 –25 0 25 50

3470 G03

TYPICAL PERFOR A CE CHARACTERISTICS UW VIN Quiescent Current vs Temperature BIAS Quiescent Current (Bias > 3V) vs Temperature SHDN Bias Current vs Temperature FB Bias Current (VFB = 1V) vs Temperature Top and Bottom Switch Current Limits (VFB = 0V) vs Temperature TEMPERATURE (°C) –5 0 CURRENT LIMIT (mA) 350

3470 G04

–2 5 0 5 0 400 300 250 150 75 100 125 TEMPERATURE (°C) –50 –25 VIN CURRENT (µA) 0 50 75

3470 G05

BIAS < 3V BIAS > 3V TEMPERATURE (°C) –50 BIAS CURRENT (µA) 20 25 75

3470 G06

–25 0 50 100 125 TEMPERATURE (°C) –50 SHDN CURRENT (µA)

3470 G07

0–25 75 10025 125 VSHDN = 36V VSHDN = 2.5V TEMPERATURE (°C) –50 –25 FB CURRENT (nA) 0 50 75

3470 G08

FB Bias Current (VFB = 0V) vs Temperature TEMPERATURE (°C) –50 FB CURRENT (µA) 80 100 120 25 75

3470 G09

–25 0 50 100 125 Switch VCESAT (ISW = 100mA) vs Temperature Boost Diode VF (IF = 50mA) vs Temperature TEMPERATURE (°C) –50 SWITCH VCESAT (mV)200 250 300 25 75

3470 G10

–25 0 50 100 125 TEMPERATURE (°C) –5 0 SCHOTTKY VF (V) 0.7

3470 G11

0.4 0.2 –2 5 0 5 0 0.1 0.8 0.6 0.5 0.3 75 100 125 Catch Diode VF (IF = 100mA) vs Temperature TEMPERATURE (°C) –50 0.4 0.5 0.7 25 75

3470 G12

0.3 0.2 –25 0 50 100 125 0.1 0.6 SCHOTTKY VF (V)

TYPICAL PERFOR A CE CHARACTERISTICS UW Switch VCESAT BOOST Pin Current Catch Diode Forward Voltage Boost Diode Forward Voltage Diode Leakage (VR = 36V) vs Temperature Minimum Input Voltage, VOUT = 3.3V Minimum Input Voltage, VOUT = 5V TEMPERATURE (°C) –50 –25 SCHOTTKY DIODE LEAKAGE (µA) 0 50 75

3470 G13

SWITCH CURRENT (mA) 400 500 700 300

3470 G14

600SWITCH VCESAT (mV) SWITCH CURRENT (mA) 300

3470 G15

BOOST PIN CURRENT (mA) CATCH DIODE CURRENT (mA) SCHOTTKY VF (V) 0.4 0.6 400

3470 G16

0.2 100 200 300 1.0 0.8 BOOST DIODE CURRENT (mA) SCHOTTKY VF (V) 500 600 700 200

3470 G17

LOAD CURRENT (mA) 3.0 INPUT VOLTAGE (V) 3.5 4.0 4.5 5.0 5.5 6.0 50 100 150 200

3470 G18

TA = 25°C VIN TO START VIN TO RUN LOAD CURRENT (mA) INPUT VOLTAGE (V) 200

3470 G19

8 TA = 25°C

SHDN (Pin 1): The SHDN pin is used to put the LT3470 in shutdown mode. Tie to ground to shut down the LT3470. Apply 2V or more for normal operation. If the shutdown feature is not used, tie this pin to the V IN pin. NC (Pin 2): This pin can be left floating or connected to VIN. VIN (Pin 3): The VIN pin supplies current to the LT3470’s internal regulator and to the internal power switch. This pin must be locally bypassed. GND (Pin 4): Tie the GND pin to a local ground plane below the LT3470 and the circuit components. Return the feed- back divider to this pin. SW (Pin 5): The SW pin is the output of the internal power switch. Connect this pin to the inductor, catch diode and boost capacitor. BOOST (Pin 6): The BOOST pin is used to provide a drive voltage, which is higher than the input voltage, to the internal bipolar NPN power switch. BIAS (Pin 7): The BIAS pin connects to the internal boost Schottky diode and to the internal regulator. Tie to VOUT when VOUT > 2V or to VIN otherwise. When VBIAS > 3V the BIAS pin will supply current to the internal regulator. FB (Pin 8): The LT3470 regulates its feedback pin to 1.25V. Connect the feedback resistor divider tap to this pin. Set the output voltage according to V OUT = 1.25V (1 + R1/R2) or R1 = R2 (VOUT/1.25 – 1). BLOCK DIAGRA W RQ ′ SQ 500ns ONE SHOT VREF 1.25V BURST MODE DETECT SW GND 3470 BD FB R2 R1 SHDN ENABLE VIN VIN NC BIAS BOOST VOUT gm 8 4

Figure 1. Operating Waveforms of the LT3470 Converting 12V to 5V Using a 33µH Inductor and 10µF Output Capacitor

3470 F01a

3470 F1b

section BOOST Pin Considerations. of the catch diode, and VOUT is the desired output voltage. tOFF-TIME possibly allowing the use of a smaller inductor. See Table 1 for an inductor value selection guide. Table 1. Recommended Inductors for Loads up to 200mA

vendors for more information. capacitor satisfies these requirements. one with low ESR intended for use in switching regulators. LIM • ESR. ESR should be less than ~150mΩ. between the output and the feedback pin. Table 2. Inductor Vendors

a low cost electrolytic capacitor. avoided; see the Hot Plugging Safely section. of 3.3V and above, the standard circuit (Figure 2a) is best. Table 3. Capacitor Vendors

3470 F02

Figure 2. Two Circuits for Generating the Boost Voltage

and BIAS pins are not exceeded. protects against a shorted or reversed input. Figure 3. The Minimum Input Voltage Depends on Output Figure 4. Diode D1 Prevents a Shorted Input from Discharging a

3470 F04

current from injecting noise into the system ground. board, and their connections should be made on that layer. ground traces will shield it from the SW and BOOST nodes. Figure 5. A Good PCB Layout Ensures Proper, Low EMI Operation

3470 F05

Figure 6: A Well Chosen Input Network Prevents Input Voltage Overshoot and Ensures Reliable Operation When the LT3470 is Connected to a Live Supply LT3470 2.2µF VIN 10V/DIV IIN 10A/DIV 10µs/DIV VIN CLOSING SWITCH SIMULATES HOT PLUG IIN (6a) (6b) (6c) LOW IMPEDANCE ENERGIZED 24V SUPPLY STRAY INDUCTANCE DUE TO 6 FEET (2 METERS) OF TWISTED PAIR LT3470 2.2µF 10µF 35V AI.EI. LT3470 2.2µF0.1µF

3470 F06

in the circuit. An alternative solution is shown in Figure 6c. A 1Ω resistor is added in series with the input to eliminate the voltage overshoot (it also reduces the peak input current). A 0.1µF capacitor improves high frequency filter- ing. This solution is smaller and less expensive than the electrolytic capacitor. For high input voltages its impact on efficiency is minor, reducing efficiency less than one half percent for a 5V output at full load operating from 24V. High Temperature Considerations The die temperature of the LT3470 must be lower than the maximum rating of 125°C. This is generally not a concern unless the ambient temperature is above 85°C. For higher temperatures, care should be taken in the layout of the circuit to ensure good heat sinking of the LT3470. The maximum load current should be derated as the ambient temperature approaches 125°C. The die temperature is calculated by multiplying the LT3470 power dissipation by the thermal resistance from junction to ambient. Power dissipation within the LT3470 can be estimated by calculating the total power loss from an efficiency mea- surement. Thermal resistance depends on the layout of the circuit board, but a value of 150 °C/W is typical. The temperature rise for an LT3470 producing 5V at 200mA is approximately 30°C, allowing it to deliver full load to 100°C ambient. Above this temperature the load current should be reduced. For 3.3V at 200mA the temperature rise is 20 °C. Finally, be aware that at high ambient temperatures the internal Schottky diode will have signifi- cant leakage current (See Typical Performance Charac- teristics) increasing the quiescent current of the LT3470 converter. APPLICATIO S I FOR ATIOWU UU

3.3V Step-Down Converter VIN BOOST LT3470 SWSHDN 0.22µF 22pF 22µF

3470 TA03

1µF VIN 5.5V TO 40V VOUT 3.3V 200mA 324k 200k C1: TDK C3216JB1H105M C2: CE JMK316 BJ226ML-T L1: TOKO A993AS-270M=P3 33µH BIAS FB GND OFF ON VIN BOOST LT3470 SWSHDN 0.22µF 22pF 22µF

3470 TA04

1µF VIN 7V TO 40V VOUT 200mA 604k 200k 33µH BIAS FB GND OFF ON C1: TDK C3216JB1H105M C2: CE JMK316 BJ226ML-T L1: TOKO A914BYW-330M=P3 5V Step-Down Converter 1.8V Step-Down Converter VIN BOOST LT3470 SWSHDN BIAS7 0.22µF 22pF 22µF 1µF VIN 4V TO 25V VOUT 1.8V 200mA 147k 332k 22µH FB GND OFF ON C1: TDK C3216JB1H105M C2: TDK C2012JB0J226M L1: MURATA LQH32CN150K53 VIN BOOST LT3470 SWSHDN 0.22µF 22pF 10µF

3470 TA06

1µF VIN 15V TO 35V VOUT 12V 200mA 866k 100k C1: TDK C3216JB1H105M C2: TDK C3216JB1C106M L1: MURATA LQH32CN150K53 33µH BIAS FB GND OFF ON 12V Step-Down Converter 2.5V Step-Down Converter VIN BOOST LT3470 SWSHDN 0.47µF 22pF 22µF

3470 TA07

1µF VIN 4.7V TO 40V VOUT 2.5V 200mA 200k 200k C1: TDK C3216JB1H105M C2: TDK C2012JB0J226M L1: SUMIDA CDRH3D28 33µH BIAS FB GND OFF ON

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 represen- tation that the interconnection of its circuits as described herein will not infringe on existing patent rights. UPACKAGE DESCRIPTIO 8-Lead Plastic TSOT-23 (Reference LTC DWG # 05-08-1637) 1.50 – 1.75 (NOTE 4)2.80 BSC 0.22 – 0.36

8 PLCS (NOTE 3)

DATUM ‘A’ 0.09 – 0.20 (NOTE 3) TS8 TSOT-23 0802

2.90 BSC

(NOTE 4)

0.65 BSC

1.95 BSC

0.80 – 0.90

1.00 MAX

0.01 – 0.100.20 BSC 0.30 – 0.50 REF PIN ONE ID NOTE: 1. DIMENSIONS ARE IN MILLIMETERS 2. DRAWING NOT TO SCALE 3. DIMENSIONS ARE INCLUSIVE OF PLATING

3.85 MAX

0.52 MAX 0.65 REF RECOMMENDED SOLDER PAD LAYOUT PER IPC CALCULATOR 1.4 MIN2.62 REF

1.22 REF

1. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR 5. MOLD FLASH SHALL NOT EXCEED 0.254mm 6. JEDEC PACKAGE REFERENCE IS MO-193

© LINEAR TECHNOLOGY CORPORATION 2004 LT/TP 1104 1K • PRINTED IN THE USA PART NUMBER DESCRIPTION COMMENTS LT1613 550mA (I SW), 1.4MHz, High Efficiency Step-Up V IN: 0.9V to 10V, VOUT(MAX) = 34V, IQ = 3mA, ISD < 1µA, DC/DC Converter ThinSOT Package LT1615/LT1615-1 300mA/80mA (I SW), Constant Off-Time, V IN: 1.2V to 15V, VOUT(MAX) = 34V, IQ = 20µA, ISD < 1µA, High Efficiency Step-Up DC/DC Converters ThinSOT Package LT1944/LT1944-1 (Dual) Dual Output 350mA/100mA (I SW), Constant Off-Time, V IN: 1.2V to 15V, VOUT(MAX) = 34V, IQ = 20µA, ISD < 1µA, High Efficiency Step-Up DC/DC Converters MS Package LT1945 (Dual) Dual Output, Pos/Neg, 350mA (I SW), Constant Off-Time, V IN: 1.2V to 15V, VOUT(MAX) = ±34V, IQ = 20µA, ISD < 1µA, High Efficiency Step-Up DC/DC Converter MS Package LT1961 1.5A (I SW), 1.25MHz, High Efficiency Step-Up V IN: 3V to 25V, VOUT(MAX) = 35V, IQ = 0.9mA, ISD < 6µA, DC/DC Converter MS8E Package LTC 3400/LTC3400B 600mA (I SW), 1.2MHz, Synchronous Step-Up V IN: 0.85V to 5V, VOUT(MAX) = 5V, IQ = 19µA/300µA, ISD < 1µA, DC/DC Converter ThinSOT Package LTC3401 1A (I SW), 3MHz, Synchronous Step-Up V IN: 0.5V to 5V, VOUT(MAX) = 6V, IQ = 38µA, ISD < 1µA, DC/DC Converter MS Package LT3460 0.32A (I SW), 1.3MHz, High Efficiency Step-Up V IN: 2.5V to 16V, VOUT(MAX) = 36V, IQ = 2mA, ISD < 1µA, DC/DC Converter MS8E Package LT3461/LT3461A 0.3A (I SW), 1.3MHz/3MHz, High Efficiency Step-Up V IN: 2.5V to 16V, VOUT(MAX) = 38V, IQ = 2.8mA, ISD < 1µA, DC/DC Converters SC70, ThinSOT Packages LT3464 0.08A (I SW), High Efficiency Step-Up DC/DC Converter V IN: 2.3V to 10V, VOUT(MAX) = 34V, IQ = 25µA, ISD < 1µA, with Integrated Schottky, Output Disconnect ThinSOT Package RELATED PARTS Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com