Datasheet

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October 2007 Rev 10 1/15

L5972D

2A switch step down switching regulator

Features

■ 2A internal switch

■ Operating input voltage from 4.4V to 36V

■ Output voltage adjustable from 1.235V to 35V

■ Low dropout operation: 100% duty cycle

■ 250kHz Internally fixed frequency

■ Voltage feedforward

■ Zero load current operation

■ Internal current limiting

■ 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 L5972D is a step down monolithic power

switching regulator with a minimum switch current

limit of 2A so it is able to deliver more than 1.5A

DC current to the load depending on the

application conditions.

The output voltage can be set from 1.235V 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

D03IN1436

L5972D

10µF

35V

CERAMIC

100µF

10V

VOUT=3.3V

VIN = 4.4V to 35V

5.6K

3.3K

4.7K

22nF

220pF

L1 33µH

STPS2L40U

COMP

VCC OUT

GND

Summary of content (15 pages)

PAGE 1
L5972D 2A switch step down switching regulator Features ■ 2A internal switch ■ Operating input voltage from 4.4V to 36V ■ Output voltage adjustable from 1.
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Contents L5972D 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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L5972D Pin settings 1 Pin settings 1.1 Pin connection Figure 2. Pin connection (top view) OUT 1 8 VCC GND 2 7 GND GND 3 6 GND COMP 4 5 FB D02IN1367 1.2 Pin description Table 1. Pin description N° Pin Description 1 OUT Regulator output. 2,3,6,7 GND Ground. 4 COMP 5 FB 8 VCC E/A output for frequency compensation. Feedback input. Connecting directly to this pin results in an output voltage of 1.23V. An external resistive divider is required for higher output voltages.
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Electrical data L5972D 2 Electrical data 2.1 Maximum ratings Table 2. Absolute maximum ratings Symbol Unit 40 V V V Input voltage V1 Out pin DC voltage Out pin peak voltage at ∆t = 0.1µs -1 to 40 -5 to 40 I1 Maximum output current int. limit. Ptot Tj Tstg Analog pins 4 V 1.2 W Operating junction temperature range -40 to 150 °C Storage temperature range -55 to 150 °C SO8 Unit (1) °C/W Power dissipation at TA ≤ 70°C Thermal data Table 3.
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L5972D 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 2 2.5 3 A 212 250 280 kHz 225 250 275 kHz 100 % 4.4 (1) VCC = 4.
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Typical characteristics 4 L5972D Typical characteristics Figure 3. Vo (V) 3.312 Output voltage vs. junction temperature Figure 4. Quiescent current vs. junction temperature Iq (mA) 2 Vcc = 12V Vo = 3.3V 3.308 3.304 1.8 Tj = 25°C 3.3 3.296 1.6 3.292 3.288 1.4 3.284 Vcc = 12V DC = 0% Tj = 125°C 3.28 1.2 3.276 0 0.5 1 -50 1.5 0 Io (A) Figure 5. Line regulator Figure 6. Vcc = 12V Vo = 3.3V 3.304 100 150 Shutdown current vs. junction temperature Ishd (µA) 70 Vo (V) 3.312 3.
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L5972D 5 Application circuit Application circuit In figure 8 is shown the demo board application circuit for the device in SMD version, where the input supply voltage, Vcc, can range from 4.4V to 25V due to the rated voltage of the input capacitor and the output voltage is adjustable from 1.235V to Vcc. Figure 9. Demo board application circuit VCC VIN = 4.4V to 25V COMP C1 10µF 25V CERAMIC D1 STPS2L25U 4 2 3 L1 33µH OUT L5972D 6 C4 22nF C3 220pF 1 8 7 VOUT=3.3V R1 5.
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Application circuit L5972D Figure 10. PCB layout (component side) Figure 11. PCB layout (bottom side) Figure 12. PCB layout (front side) Sideways two graphs show the TJ versus output current in different conditions of the input and output voltage.
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L5972D Application circuit Figure 13. Junction temperature vs output current Figure 14. Efficiency vs output current 95 TJ(°C) 93 100.0 Vo=3.3V 91 Vo=2.5V Vin=5V Tamb.=25 °C 80.0 89 Vo=3.3V 87 70.0 Efficiency (%) 90.0 Vo=1.8V 60.0 50.0 85 Vo=2.5V 83 81 79 Vo=1.8V 77 75 40.0 73 Vin=5V 71 30.0 69 20.0 67 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 0.1 0.3 0.5 0.7 Io(A) 1.1 1.3 1.5 1.7 Io (A) Figure 15. Junction temperature vs output current Figure 16.
PAGE 10
Application ideas 6 L5972D Application ideas Figure 17. Positive buck-boost regulator 8 L5972D 6 2 C3 22nF R3 4.7k D1 STPS2L25U FB 4 C2 220pF D2 STPS2L25U VOUT=12V/0.45A 1 COMP C1 10uF 10V Ceramic L1 33uH OUT Vcc VIN=5V 24k 5 3 7 C4 100uF 16V M1 STN4NE03L GND 2.7k Figure 18. Buck-boost regulator VIN=5V 8 1 COMP C2 10uF C3 25V Ceramic 220pF C1 10uF 10V Ceramic L1 33uH OUT Vcc L5972D FB 4 2 6 C4 22nF R3 4.7k 7 5 3 D1 STPS2L25U 2.7k GND 24k VOUT=-12V/0.
PAGE 11
L5972D 7 Package mechanical data 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.
PAGE 12
Package mechanical data Table 6. L5972D 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 D (1) 4.80 5.00 0.189 0.197 E 3.80 4.00 0.15 0.157 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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L5972D 8 Order codes Order codes Table 7.
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Revision history 9 L5972D Revision history Table 8.
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L5972D 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.