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April 2007 Rev 7 1/17

L4976

1A step down switching regulator

Features

■ Up to 1A step down converter

■ Operating input voltage from 8v to 55v

■ Precise 5.1V reference voltage

■ Output voltage adjustable from 0.5V to 50V

■ Switching frequency adjustable up to 300kHz

■ Voltage feedforward

■ Zero load current operation

■ Internal current limiting (pulse-bypulse

■ and hiccup mode)

■ Protection against feedback disconnection

■ Thermal shutdown

Description

The L4976 is a step down monolithic power

switching regulator delivering 1A at a voltage

between 3.3V and 50V (selected by a simple

external divider). Realized in BCD mixed

technology, the device uses an internal power D-

MOS transistor (with a typical R

ds(ON)

of 0.25Ω) to

obtain very high efficency and high switching

speed. A switching frequency up to 300KHz is

achievable (the maximum power dissipation of the

packages must be observed). A wide input

voltage range between 8V to 55V and output

voltages regulated from 3.3V to 40V cover the

majority of today’s applications. Features of this

new generations of DC-DC converter include

pulse-by-pulse current limit, hiccup mode for short

circuit protection, voltage feedforward regulation,

protection against feedback loop disconnection

and thermal shutdown. The device is available in

plastic dual in line, MINIDIP 8 for standard

assembly, and SO16W for SMD assembly.

DIP8 SO16W

www.st.com

Figure 1. Typical application circuit

L4976

220µF

63V

330µF

=3.3V/1A

Vi=8V to 55V

20K

2.7nF

9.1K

22nF

260µH

(77120)

SB360

220nF

100nF

Summary of content (17 pages)

PAGE 1
L4976 1A step down switching regulator Features ■ Up to 1A step down converter ■ Operating input voltage from 8v to 55v ■ Precise 5.1V reference voltage ■ Output voltage adjustable from 0.5V to 50V ■ Switching frequency adjustable up to 300kHz ■ Voltage feedforward ■ Zero load current operation ■ Internal current limiting (pulse-bypulse ■ and hiccup mode) ■ Protection against feedback disconnection ■ Thermal shutdown Figure 1.
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Contents L4976 Contents 1 Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 Pin settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3 2.1 Pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.2 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Electrical data . . . . .
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L4976 1 Block diagram Block diagram Figure 2. Block diagram VCC 5 THERMAL SHUTDOWN VOLTAGES MONITOR CBOOT CHARGE VREF 2 VREF 5.1V COMP FB INTERNAL REFERENCE 7 8 6 3.3V E/A PWM R Q S 3.
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Pin settings L4976 2 Pin settings 2.1 Pin connection Figure 3. Pin connection (top view) GND 1 8 FB VREF 2 7 COMP OSC 3 6 BOOT OUT 4 5 VCC N.C. 1 16 N.C. GND 2 15 N.C. VREF 3 14 FB OSC 4 13 COMP OUT 5 12 BOOT OUT 6 11 VCC N.C. 7 10 N.C. N.C. 8 9 N.C. SO16 DIP8 2.2 Pin description Table 1. Pin description N° Pin Name Description DIP8 SO16W (1) 1 2 GND Ground 2 3 VREF 5.1V Reference voltage with 20mA current capability.
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L4976 Electrical data 3 Electrical data 3.1 Maximum ratings Table 2. Absolute maximum ratings Symbol Parameter DIP8 S016W V5 V11 V4 V5, V6 I4 I5, I6 V6-V5 V12-V11 V6 V12 V7 V8 Unit Input voltage 58 V Output DC voltage -1 V Output peak voltage at t = 0.1µs, f = 200kHz -5 V Maximum output current internal limit 14 V Bootstrap voltage 70 V V13 Analogs input voltage (VCC = 24V) 12 V (VCC = 20V) 6 V V14 -0.3 V DIP8 1 W SO16 0.8 W -40 to 150 °C PTOT TJ,TSTG 3.
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Electrical characteristics 4 L4976 Electrical characteristics Table 5. Electrical characteristics (TJ = 25°C, COSC = 2.7nF, ROSC = 20kΩ, VCC = 24V, unless otherwise specified.) Symbol Parameter Test condition Min Typ Max Unit 55 V Dynamic characteristic VI VO Vd Operating input voltage range Output voltage Dropout voltage VO = 3.3 to 50V; IO = 1A (1) 8 IO = 0.5A 3.33 3.36 3.39 V IO = 0.2 to 1A 3.292 3.36 3.427 V VCC = 8 to 55V (1) 3.22 3.36 3.5 V 0.29 0.367 V 0.
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L4976 Electrical characteristics Table 5. Electrical characteristics (continued) (TJ = 25°C, COSC = 2.7nF, ROSC = 20kΩ, VCC = 24V, unless otherwise specified.) Symbol Parameter Test condition Min Typ Max Unit 4 6 mA 2.5 3.5 mA 3.36 3.39 V 5 10 mV DC Characteristics Iqop Iq Total operating quiescent current Quiescent current Duty Cycle = 0; VFB = 3.8V Error Amplifier VFB Voltage feedback input RL Line regulation Ref. voltage stability vs temperature 3.
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Typical charcteristics 5 L4976 Typical charcteristics Figure 4. Quiescent drain current vs. input voltage Iq (mA) D97IN724 200KHz R1=22K C2=1.2nF 5 Line regulation VO (V) 3.378 D97IN734 VCC=35V 3.376 3.374 100KHz R1=20K C2=2.7nF 4 Figure 5. Tj=25˚C 3.372 3.370 3 Tj=125˚C 3.368 0Hz 3.366 3.364 2 Tamb=25˚C 0% DC 3.362 3.360 1 0 Figure 6. 0 Vcc(V) 5 10 15 20 25 30 35 40 45 50 Quiescent current vs. junction Figure 7. temperature D97IN731 Iq (mA) 4 Switching frquency vs.
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L4976 Typical charcteristics Figure 8. Load regulation Figure 9. VO (V) D97IN733 3.377 Switching frequency vs. input voltage fsw (KHz) D97IN735 107.5 Tj=125˚C 105.0 3.376 102.5 3.375 Tj=25˚C Tj=25˚C 3.374 100.0 3.373 97.5 3.372 95.0 3.371 92.5 90.0 3.370 0 0 5 10 15 20 25 30 35 40 45 50 VCC(V) Figure 10. Switching frequency vs. junction temperature fsw (KHz) 5 10 15 20 25 30 35 40 45 50 VCC(V) Figure 11. Efficiency vs. output current D97IN785 ∆V (V) D97IN736 Tj=125˚C 0.
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Typical charcteristics L4976 Figure 14. Efficiency vs output voltage η (%) D97IN737 100KHz 96 94 Figure 15. Efficiency vs. output current D97IN740 η (%) VCC=8V 90 200KHz VCC=12V VCC=24V 85 92 80 VCC=48V 90 75 VCC=35V IO=1.5A 88 86 70 84 65 82 0 5 10 15 20 25 VO(V) Figure 16. Efficiency vs. output current η (%) D97IN741 fsw=200KHz VO=5.1V 60 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A) Figure 17. Efficiency vs.
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L4976 Typical charcteristics Figure 20. Power dissipation vs. VCC Pdiss (mW) Figure 21. Load transient D97IN743 VO=5.1V fsw=100KHz 800 IO=1.5A 600 IO=1A 400 IO=0.5A 200 0 0 10 20 30 40 50 VCC(V) Figure 22. Line transient VCC (V) Figure 23.
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Package mechanical data 6 L4976 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. ECOPACK specifications are available at: www.
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L4976 Package mechanical data Figure 24. DIP8 mechanical data & package dimensions mm inch DIM. MIN. A TYP. MAX. MIN. 3.32 TYP. MAX. 0.131 a1 0.51 B 1.15 1.65 0.045 0.065 b 0.356 0.55 0.014 0.022 b1 0.204 0.304 0.008 0.012 0.020 D E 10.92 7.95 9.75 0.430 0.313 0.384 e 2.54 0.100 e3 7.62 0.300 e4 7.62 0.300 F 6.6 0.260 I 5.08 0.200 L Z 3.18 OUTLINE AND MECHANICAL DATA 3.81 1.52 0.125 0.150 DIP-8 0.
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Package mechanical data L4976 Figure 25. SO16Wide mechanical data & package dimensions mm inch DIM. MIN. TYP. MAX. MIN. TYP. MAX. A 2.35 2.65 0.093 0.104 A1 0.10 0.30 0.004 0.012 B 0.33 0.51 0.013 0.200 C 0.23 0.32 0.009 0.013 D (1) 10.10 10.50 0.398 0.413 E 7.40 7.60 0.291 0.299 e 1.27 0.050 H 10.0 10.65 0.394 0.419 h 0.25 0.75 0.010 0.030 L 0.40 1.27 0.016 0.050 k ddd OUTLINE AND MECHANICAL DATA 0˚ (min.), 8˚ (max.) 0.10 0.
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L4976 7 Order code Order code Table 6.
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Revision history 8 L4976 Revision history Table 7.
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L4976 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.