Datasheet

ManualsBrandsLinear Technology ManualsDC / DC Adjustable Switching RegulatorsSwitching Regulator IC Step-Down TSOT-23-1.3 ... 20V

LT1616

600mA, 1.4MHz Step-Down

Switching Regulator

in SOT-23

, LTC and LT are registered trademarks of Linear Technology Corporation.

The LT

1616 is a current mode PWM step-down DC/DC

converter with internal 0.6A power switch, packaged in a

tiny 6-lead SOT-23. The wide input range of 3.6V to 25V

makes the LT1616 suitable for regulating a wide variety of

power sources, from 4-cell batteries and 5V logic rails to

unregulated wall transformers and lead-acid batteries. Its

high operating frequency allows the use of tiny, low cost

inductors and ceramic capacitors. With its internal com-

pensation eliminating additional components, a complete

400mA step-down regulator fits onto 0.15 square inches

of PC board area.

The constant frequency current mode PWM architecture

and stable operation with ceramic capacitors results in

low, predictable output ripple. Current limiting provides

protection against shorted outputs. The low current (<1µA)

shutdown provides complete output disconnect, enabling

easy power management in battery-powered systems.

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Wide Input Range: 3.6V to 25V

■

5V at 400mA from 7V to 25V Input

■

3.3V at 400mA from 4.7V to 25V Input

■

Fixed Frequency 1.4MHz Operation

■

Uses Tiny Capacitors and Inductors

■

Internally Compensated

■

Low Shutdown Current: <1µA

■

Low V

CESAT

Switch: 220mV at 300mA

■

Tiny 6-Lead SOT-23 Package

■

Wall Transformer Regulation

■

Local Logic Supply Conversion:

12V to 5V

12V or 5V to 3.3V, 2.5V or 1.8V

■

Distributed Supply Regulation

■

Digital Cameras

■

Battery-Powered Equipment

3.3V Step-Down Converter

BOOST

GND FB

SHDN SW

4.5V TO 25V

OFF ON

0.01µF

10µH

10k

16.5k

LT1616

10µF

1616 TA01

1µF

OUT

3.3V

300mA: V

= 4.5V TO 25V

400mA: V

= 4.7V TO 25V

C1: TAIYO-YUDEN TMK316BJ105

C2: TAIYO-YUDEN JMK316BJ106ML

D1: ON SEMICONDUCTOR MBR0530

D2: 1N4148

L1: SUMIDA CR43-100

Efficiency

LOAD CURRENT (mA)

100

300 400

1616 G02

100 200 500

EFFICIENCY (%)

= 5V

= 20V

= 12V

FEATURES

DESCRIPTIO

APPLICATIO S

TYPICAL APPLICATIO

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Summary of content (16 pages)

PAGE 1
LT1616 600mA, 1.4MHz Step-Down Switching Regulator in SOT-23 U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO The LT ®1616 is a current mode PWM step-down DC/DC converter with internal 0.6A power switch, packaged in a tiny 6-lead SOT-23. The wide input range of 3.6V to 25V makes the LT1616 suitable for regulating a wide variety of power sources, from 4-cell batteries and 5V logic rails to unregulated wall transformers and lead-acid batteries.
PAGE 2
LT1616 W W W AXI U U ABSOLUTE RATI GS U U W PACKAGE/ORDER I FOR ATIO (Note 1) Input Voltage (VIN) ................................................. 25V BOOST Pin Voltage ................................................. 35V BOOST Pin Above SW Pin ...................................... 25V SHDN Pin ............................................................... 25V FB Voltage ................................................................ 6V Current Into FB Pin ......................................
PAGE 3
LT1616 U W TYPICAL PERFOR A CE CHARACTERISTICS Efficiency, VOUT = 5V Efficiency, VOUT = 3.3V 100 90 VIN = 12V VIN = 24V 70 VIN = 12V 400 80 EFFICIENCY (%) 80 VIN = 5V SWITCH VOLTAGE (mV) VIN = 8V 90 60 60 50 50 40 40 30 VIN = 20V 70 100 200 500 300 400 LOAD CURRENT (mA) 0 100 200 BOOST Pin Current 500 500 16 L = 10µH L = 15µH LOAD CURRENT (mA) L = 6.8µH 300 OUTPUT LIMITED BY DISSIPATION 200 600 200 400 SWITCH CURRENT (mA) 1616 G03 Maximum Load Current at VOUT = 3.
PAGE 4
LT1616 U W TYPICAL PERFOR A CE CHARACTERISTICS Oscillator Frequency SHDN Pin Current 120 2.00 100 SHDN PIN CURRENT (µA) SWITCHING FREQUENCY (MHz) 1.75 1.50 1.25 1.00 0.75 0.50 60 40 20 0.25 0 –50 80 0 –25 0 50 25 TEMPERATURE (°C) 75 100 1616 G09 0 5 10 15 20 SHDN PIN VOLTAGE 25 1616 G10 U U U PI FU CTIO S BOOST (Pin 1): The BOOST pin is used to provide a drive voltage, higher than the input voltage, to the internal bipolar NPN power switch.
PAGE 5
LT1616 W BLOCK DIAGRA VIN 5 SHDN 4 1 BOOST INT REG AND UVLO SLOPE COMP Σ R Q S Q DRIVER OSC Q1 6 SW FREQUENCY FOLDBACK VC gm 1.25V U OPERATIO 2 3 GND FB 1616BD (Refer to Block Diagram) The LT1616 is a constant frequency, current mode Buck regulator. The 1.4MHz oscillator enables an RS flip-flop, turning on the internal 600mA power switch Q1.
PAGE 6
LT1616 U W U U APPLICATIO S I FOR ATIO The LT1616 efficiently converts power from an input voltage source to a lower output voltage using an inductor for energy storage. The LT1616 uses its internal power switch and an external catch diode (D1 of the application circuit on the first page of this data sheet) to produce a pulsewidth modulated square wave. Inductor L1 and output capacitor C2 filter this square wave to produce a DC output voltage.
PAGE 7
LT1616 U W U U APPLICATIO S I FOR ATIO Inductor Selection and Maximum Output Current The duty cycle of the internal switch is: DC = (VOUT + VD)/(VIN – VSW + VD) where VD is the forward voltage drop of the catch diode (D1) and VSW is the voltage drop of the internal switch. Usually one is interested in DC at full load current, so you can use VD = VSW = 0.4V. Note that the LT1616 has a maximum guaranteed duty cycle of 0.8. This will limit the minimum input voltage for a particular output voltage.
PAGE 8
LT1616 U W U U APPLICATIO S I FOR ATIO Table 1. Inductor Vendors Vendor Phone URL Part Series Comments Murata (404) 426-1300 www.murata.com LQH3C Small, Low Cost, 2mm Height Sumida (847) 956-0666 www.sumida.com CR43 CLS62 CLQ61 1:1 Coupled 1.5mm Height Coilcraft (847) 639-6400 www.coilcraft.com DO1607C DO1608C DT1608C Coiltronics (407) 241-7876 www.coiltronics.com CTXxx-1 TP1 www.tokoam.com 3DF D52LC Toko 1:1 Coupled Toroid 1.8mm Height Table 2.
PAGE 9
LT1616 U W U U APPLICATIO S I FOR ATIO VIN 10V 5 VIN BOOST 1 LT1616 4 SHDN GND 2 SW 6 10µH VOUT 3.3V FB 22Ω 3 33Ω COUT COUT = 4.7µF CERAMIC, CASE SIZE 0805 1616 F04 Figure 4. Circuit Used for Transient Load Test Shown in Figure 3 COUT = 10µF CERAMIC, CASE SIZE 1206 COUT = 47µF, ESR ≅ 0.080Ω (SANYO POSCAP 6TPA47M) C CASE COUT = 100µF, ESR ≅ 0.
PAGE 10
LT1616 U W U U APPLICATIO S I FOR ATIO Capacitor C3 and diode D2 are used to generate a boost voltage that is higher than the input voltage. In most cases a 0.01µF capacitor and fast switching diode (such as the 1N4148 or 1N914) will work well. Figure 5 shows two ways to arrange the boost circuit. The BOOST pin must be more than 2.5V above the SW pin for best efficiency. For outputs of 3.3V and above, the standard circuit (Figure 5a) is best. For outputs between 2.8V and 3.3V, use a 0.
PAGE 11
LT1616 U W U U APPLICATIO S I FOR ATIO the SHDN pin, the SW pin current will drop to essentially zero. However, if the VIN pin is grounded while the output is held high, then parasitic diodes inside the LT1616 can pull large currents from the output through the SW pin and the VIN pin. Figure 7 shows a circuit that will run only when the input voltage is present and that protects against a shorted or reversed input.
PAGE 12
LT1616 U W U U APPLICATIO S I FOR ATIO catch diode (D1) and the input capacitor (C1). The loop formed by these components should be as small as possible. Furthermore, the system ground should be tied to the regulator ground in only one place; this prevents the switched current from injecting noise into the system ground. These components, along with the inductor and output capacitor, should be placed on the same side of the circuit board, and their connections should be made on that layer.
PAGE 13
LT1616 U TYPICAL APPLICATIO S 12V Output D4 VIN 16V TO 25V 5 VIN BOOST C3 0.01µF LT1616 OFF ON 4 SHDN SW GND 6 FB 2 R1 86.6k 3 C1 1µF 25V D3 D2 1 L1 33µH VOUT 12V 300mA D1 C2 2.2µF 16V R2 10k GND 1616 TA03 C1: TAIYO-YUDEN TMK316BJ105ML C2: TAIYO-YUDEN EMK316BJ225ML D1: ON SEMICONDUCTOR MBR0530 D2, D4: 1N4148 D3: CMPZ5234B 6.2V ZENER. D3 LIMITS BOOST PIN VOLTAGE TO VIN + 6V L1: COILCRAFT DO1608C-333 1.8V Output D2 VIN 3.
PAGE 14
LT1616 U TYPICAL APPLICATIO S 2.5V Output D2 5 VIN 3.6V TO 16V VIN 1 BOOST C3 0.01µF LT1616 4 OFF ON SHDN 6 SW GND FB 2 R1 10k 3 C1 1µF 16V L1 4.7µH VOUT 2.5V 350mA D1 C2 4.7µF 6.3V R2 10k GND 1616 TA05 C1: TAIYO-YUDEN EMK212BJ105MG C2: TAIYO-YUDEN JMK212BJ475MG D1: ON SEMICONDUCTOR MBR0520 D2: 1N4148 L1: MURATA LQH3C4R7M24 5V Output VIN 7V TO 25V 5 VIN BOOST LT1616 OFF ON 4 SHDN GND 2 C1 1µF 25V SW FB 3 6 R1 30.
PAGE 15
LT1616 U PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. S6 Package 6-Lead Plastic SOT-23 (LTC DWG # 05-08-1634) 2.80 – 3.00 (0.110 – 0.118) (NOTE 3) 1.90 (0.074) REF 2.6 – 3.0 (0.110 – 0.118) 1.50 – 1.75 (0.059 – 0.069) 0.35 – 0.55 (0.014 – 0.022) 0.00 – 0.15 (0.00 – 0.006) 0.09 – 0.20 (0.004 – 0.008) (NOTE 2) 0.95 (0.037) REF 0.90 – 1.45 (0.035 – 0.057) 0.35 – 0.50 0.90 – 1.30 (0.014 – 0.020) (0.035 – 0.051) SIX PLACES (NOTE 2) S6 SOT-23 0898 NOTE: 1.
PAGE 16
LT1616 U TYPICAL APPLICATION Bipolar Output DC/DC Converter VIN 7.5V TO 25V 5 VIN BOOST LT1616 OFF ON 4 SHDN GND SW FB 2 C1 1µF 25V 3 D2 1 6 C3 0.01µF L1A 22µH • R1 30.1k 5V 200mA D1 C2 10µF 6.3V R2 10k C1: TAIYO-YUDEN TMK316BJ105ML C2, C4: TAIYO-YUDEN JMK316BJ106ML C5: TAIYO-TUDEN JMK107BJ105MA D1, D3: ON SEMICONDUCTOR MBR0530 D2: 1N4148 L1: 22µH 1:1 SUMIDA CLS62-220 OR COILTRONICS CTX20-1 –5V LOAD SHOULD BE LESS THAN 1/2 5V LOAD, SEE DESIGN NOTE 100 C5 1µF 6.