Datasheet

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October 2007 Rev 16 1/16

L5970D

Up to 1A step down switching regulator

Features

■ Up to 1A output current

■ Operating input voltage from 4.4V to 36V

■ 3.3V / (±2%) reference voltage

■ Output voltage adjustable from 1.2V to 35V

■ Low dropout operation: 100% duty cycle

■ 250KHz Internally fixed frequency

■ Voltage feedforward

■ Zero load current operation

■ Internal current limiting

■ Inhibit for zero current consumption

■ Synchronization

■ Protection against feedback disconnection

■ Thermal shutdown

Applications

■ Consumer: STB, DVD, TV, VCR, car radio,

LCD monitors

■ Networking: XDSL, modems, DC-DC modules

■ Computer: printers, audio/graphic cards,

optical storage, hard disk drive

■ Industrial: changers, car battery, DC-DC

converters

Figure 1. Test application circuit

Description

The L5970D is a step down monolithic power

switching regulator capable to deliver up to 1A at

output voltages from 1.2V to 35V.

The device uses an internal P-Channel D-MOS

transistor (with a typical Rdson of 250mΩ) as

switching element to minimize the size of the

external components.

An internal oscillator fixes the switching frequency

at 250KHz.

Having a minimum input voltage of 4.4V only, it is

particularly suitable for 5V bus, available in all

computer related applications.

Pulse by pulse current limit with the internal

frequency modulation offers an effective constant

current short circuit protection.

SO8

www.st.com

D98IN954C

L5970D

10µF

35V

CERAMIC

100µF

10V

VOUT=3.3V

VIN = 4.4V to 35V

5.6K

3.3K

4.7K

22nF

220pF

STPS2L40U

3.3V

INH.

SYNC.

COMP

VCC

VREF

OUT

GND

L1 33µH

Summary of content (16 pages)

PAGE 1
L5970D Up to 1A step down switching regulator Features ■ Up to 1A output current ■ Operating input voltage from 4.4V to 36V ■ 3.3V / (±2%) reference voltage ■ Output voltage adjustable from 1.2V to 35V ■ Low dropout operation: 100% duty cycle ■ 250KHz Internally fixed frequency Description ■ Voltage feedforward ■ Zero load current operation ■ Internal current limiting The L5970D is a step down monolithic power switching regulator capable to deliver up to 1A at output voltages from 1.
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Contents L5970D Contents 1 2 Pin settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1 Pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.2 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Electrical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.1 Maximum ratings . . .
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L5970D Pin settings 1 Pin settings 1.1 Pin connection Figure 2. Pin connection (top view) OUT 1 8 VCC SYNC 2 7 GND INH 3 6 VREF COMP 4 5 FB D98IN955 1.2 Pin description Table 1. Pin description N° Type Description 1 OUT 2 SYNC 3 INH 4 COMP 5 FB 6 VREF 3.3V VREF. No cap is requested for stability. 7 GND Ground. 8 VCC Unregulated DC input voltage. Regulator output. Master/slave synchronization. A logical signal (active high) disables the device.
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Electrical data L5970D 2 Electrical data 2.1 Maximum ratings Table 2. Absolute maximum ratings Symbol Value Unit 40 V V V V8 Input voltage V1 Output DC voltage Output peak voltage at t = 0.1µs -1 to 40 -5 to 40 I1 Maximum output current int. limit. V4, V5 Analog pins V3 INH V2 SYNC PTOT TJ TSTG 2.2 Parameter 4 V -0.3V to VCC -0.3 to 4 V 0.
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L5970D 3 Electrical characteristics Electrical characteristics Table 4. Electrical characteristics ( TJ = 25°C, VCC = 12V, unless otherwise specified) Symbol VCC RDS(on) Parameter Operating input voltage range Test condition Vo = 1.235V; Io = 2A Mosfet on Resistance Il Maximum limiting current fs Switching frequency Min (1) Max Unit 36 V 0.250 0.5 Ω 1.5 1.87 2.25 A 212 250 280 KHz 225 250 275 KHz 100 % 4.4 (1) VCC = 4.
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Electrical characteristics L5970D Table 4. Electrical characteristics (continued) ( TJ = 25°C, VCC = 12V, unless otherwise specified) Symbol Parameter Io sink Sink output current Ib Source bias current gm Test condition VCOMP = 1.9V; VFB = 1.5V Min Typ 1 1.5 2.5 DC open loop gain RL = ∞ Transconductance Icomp = -0.1mA to 0.1mA VCOMP = 1.9V High input voltage VCC = 4.4V to 36V Low input voltage VCC = 4.4V to 36V Slave sink current Vsync = 0.74V (2) Vsync = 2.
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L5970D 4 Typical characteristics Typical characteristics Figure 3. Junction temperature vs output current Figure 4. Vo (V) 3.312 Tj(°C) 130 120 110 100 90 80 70 60 50 40 30 20 Vo=3.3V Vcc=5V Tamb=25°C Vo=2.5V Vo=1.8V Load regulator Vcc = 12V Vo = 3.3V 3.308 3.304 Tj = 25°C 3.3 3.296 3.292 3.288 3.284 Tj = 125°C 3.28 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 3.276 0 0.5 Figure 5. 1 1.5 Io (A) Io(A) Junction temperature vs output current Figure 6. Line regulator Vo (V) Tj(°C) 3.
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Typical characteristics L5970D Figure 9. Quiescent current vs junction temperature Figure 10. Switching frequency vs junction temperature Iq (mA) 2 Fsw (KHz) 260 1.8 250 1.6 240 Vcc = 12V DC = 0% 1.4 Vcc = 12V Vo = 3.3V 230 1.2 220 -50 0 50 Tj (°C) 100 150 -50 0 50 Tj (C) 100 150 Figure 11. Shutdown current vs junction Figure 12.
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L5970D 5 Application circuit Application circuit Figure 14. Demo board application circuit VREF 3.3V VIN = 4.4V to 25V VCC SYNC. C1 10µF 25V CERAMIC COMP C4 22nF C3 220pF 6 1 8 D1 STPS2L25U L5970D 2 3 4 INH. 7 L1 33µH OUT 5 FB GND VOUT=3.3V R1 5.6K C2 100µF 10V R2 3.3K R3 4.7K D03IN1437 Table 5.
PAGE 10
Application circuit Figure 15. PCB layout (component side) Figure 16. PCB layout (bottom side) Figure 17.
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L5970D 6 Application ideas Application ideas Figure 18. Dual output voltage with auxiliary winding N1/N2=2 VIN=12V VCC COMP C1 10uF 25V Ceramic 1 C3 22nF R3 4.7k FB 4 6 5 3 7 SYNC VREF VOUT=3.3V 0.5A D1 STPS25L25U U1 L5970D 2 C2 220pF VOUT1=5V 30mA Lp=22uH OUT 8 D2 1N4148 GND C4 100uF 10V C5 47uF 10V INH 3.3V Figure 19. Buck-boost regulator VIN=12V VCC 8 1 U1 C2 10uF C3 35V Ceramic 220pF Vin=12V Vout=-12V 4 2 C4 22nF R3 4.
PAGE 12
Package mechanical data 7 L5970D Package mechanical data In order to meet environmental requirements, ST offers these devices in ECOPACK® packages. These packages have a Lead-free second level interconnect . The category of second level interconnect is marked on the package and on the inner box label, in compliance with JEDEC Standard JESD97. The maximum ratings related to soldering conditions are also marked on the inner box label. ECOPACK is an ST trademark.
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L5970D Package mechanical data Table 6. SO-8 mechanical data mm. inch Dim. Min Typ Max Min Typ Max A 1.35 1.75 0.053 0.069 A1 0.10 0.25 0.004 0.010 A2 1.10 1.65 0.043 0.065 B 0.33 0.51 0.013 0.020 C 0.19 0.25 0.007 0.010 (1) 4.80 5.00 0.189 0.197 E 3.80 4.00 0.15 0.157 D e 1.27 0.050 H 5.80 6.20 0.228 0.244 h 0.25 0.50 0.010 0.020 L 0.40 1.27 0.016 0.050 k ddd 0° (min.), 8° (max.) 0.10 0.004 1.
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Order codes 8 L5970D Order codes Table 7.
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L5970D 9 Revision history Revision history Table 8.
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L5970D Please Read Carefully: Information in this document is provided solely in connection with ST products. STMicroelectronics NV and its subsidiaries (“ST”) reserve the right to make changes, corrections, modifications or improvements, to this document, and the products and services described herein at any time, without notice. All ST products are sold pursuant to ST’s terms and conditions of sale.