Datasheet

ManualsBrandsST ManualsDC / DC Adjustable Switching RegulatorsSwitching Voltage Regulator, Step-Down, 2.5A, 250kHz, HSOP

January 2008 Rev 16 1/17

L5973D

2.5 A switch step down switching regulator

Features

■ 2.5 A internal switch

■ Operating input voltage from 4 V to 36 V

■ 3.3 V / (±2%) reference voltage

■ Output voltage adjustable from 1.235 V to 35 V

■ Low dropout operation: 100 % duty cycle

■ 250 kHz 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 L5973D is a step down monolithic power

switching regulator with a minimum switch current

limit of 2.5 A so it is able to deliver more than 2 A

DC current to the load depending on the

application conditions.

The output voltage can be set from 1.235 V to

35 V. The high current level is also achieved

thanks to an SO8 package with exposed frame,

that allows to reduce the Rth(j-amb) down to

approximately 40 °C/W.

The device uses an internal P-channel D-MOS

transistor (with a typical Rdson of 250 mΩ) as

switching element to minimize the size of the

external components.

An internal oscillator fixes the switching frequency

at 250 kHz.

Having a minimum input voltage of 4 V only, it is

particularly suitable for 5 V 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.

HSOP8 exposed pad

www.st.com

D03IN1439

L5973D

10µF

35V

CERAMIC

330µF

10V

VOUT=3.3V

VIN = 4.4V to 35V

5.6K

3.3K

4.7K

22nF

220pF

L1 15µH

STPS340U

COMP

VCC

OUT

GNDINH

3.3V

SYNC.

VREF

Summary of content (17 pages)

PAGE 1
L5973D 2.5 A switch step down switching regulator Features ■ 2.5 A internal switch ■ Operating input voltage from 4 V to 36 V ■ 3.3 V / (±2%) reference voltage ■ Output voltage adjustable from 1.
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Contents L5973D 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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L5973D 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 3.3 V 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 L5973D 2 Electrical data 2.1 Maximum ratings Table 2. Absolute maximum ratings Symbol Unit 40 V V V Input voltage V1 Output DC voltage Output peak voltage at t = 0.1 µs -1 to 40 -5 to 40 I1 Maximum output current int. limit. Analog pins V3 INH V2 SYNC PTOT TJ TSTG 4 V -0.3 V to VCC -0.3 to 4 V 2.25 W Operating junction temperature range -40 to 150 °C Storage temperature range -55 to 150 °C Power dissipation at TA ≤ 60 °C Thermal data Table 3.
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L5973D 3 Electrical characteristics Electrical characteristics Table 4. Electrical characteristics ( TJ = 25 °C, VCC = 12 V, unless otherwise specified) Symbol VCC RDS(on) Parameter Operating input voltage range Test condition Vo = 1.235 V; Io = 2 A Mosfet on Resistance Il Maximum limiting current fs Switching frequency Min (1) Max Unit 36 V 0.250 0.5 Ω 2.5 3 3.5 A 212 250 280 kHz 225 250 275 kHz 100 % 4 (1) VCC = 4.
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Electrical characteristics Table 4. L5973D Electrical characteristics (continued) ( TJ = 25 °C, VCC = 12 V, unless otherwise specified) Symbol Ib gm Parameter Test condition Min Source bias current DC open loop gain RL = ∞ Transconductance Icomp = -0.1 mA to 0.1 mA VCOMP = 1.9 V High input voltage VCC = 4.4 V to 36 V Low input voltage VCC = 4.4 V to 36 V 50 Typ Max Unit 2.5 4 µA 57 dB 2.3 mS Sync function 2.5 (2) 0.11 0.21 VREF V 0.74 V 0.25 0.
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L5973D 4 Typical characteristics Typical characteristics Figure 3. Line regulation Figure 4. Vo (V) Ishd (µA) 70 3.312 Vcc = 12V Vo = 3.3V 3.308 3.304 Shutdown current vs junction temperature Tj = 25°C 60 3.3 Vcc = 12V 3.296 50 3.292 Tj = 125°C 3.288 40 3.284 3.28 3.276 30 0 Figure 5. 10 20 Vcc (V) 30 40 Output voltage vs junction temperature -50 Figure 6. Vo (V) 1.25 50 Tj (°C) 0 100 150 Switching frequency vs junction temperature Fsw (KHz) 260 1.24 250 1.23 240 1.
PAGE 8
Typical characteristics Figure 8. L5973D Junction temperature vs output current Tj(°C) 120 110 Vin=5V 100 Tamb=25°C 90 80 70 60 50 40 30 20 0.2 0.4 0.6 0.8 1 Figure 9. Junction temperature vs output current Tj (°C) 120 Vo=3.3V Vo=2.5V 110 100 Vo=5V Vin=12V Tamb=25°C 90 Vo=1.8V 80 Vo=2.5V 70 60 50 40 30 20 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 Io(A) Vo=1.8V Vin=5V 0.1 0.3 0.5 0.7 0.9 1.1 1.3 1.5 1.7 1.9 2.1 2.3 Io (A) 8/17 2.2 2.4 2.6 Figure 11.
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L5973D 5 Application circuit Application circuit In figure 6 is shown the demonstration board application circuit, where the input supply voltage, VCC, can range from 4 V to 25 V due to the rated voltage of the input capacitor and the output voltage is adjustable from 1.235 V to VCC. Figure 12. Demonstration board application circuit VREF 3.3V VCC VIN = 4.4V to 25V SYNC. COMP C1 10µF 25V CERAMIC C4 22nF C3 220pF 6 1 8 D1 STPS2L25U L5973D 2 3 4 INH 7 L1 15µH OUT VOUT=3.3V R1 5.
PAGE 10
Application circuit L5973D Figure 13. PCB layout (component side) Figure 14. PCB layout (bottom side) Figure 15. PCB layout (front side) Below some graphs show the TJ versus output current in different conditions of the input and output voltage and some efficiency measurements.
PAGE 11
L5973D 6 Application ideas Application ideas Figure 16. Positive buck-boost regulator Figure 17. Buck-boost regulator Figure 18.
PAGE 12
Application ideas L5973D When an output voltage below the internal reference (1.235 V) is required, the circuit reported in the figure 18 can been used. In this case the minimum voltage reachable is 0.6 V and can be easily calculated with the following formula: VOUT = VFB - [(VREF - VFB)x(R2 / R1)] If the load is not present, a resistor connected between VOUT and GND is required in order to avoid that the voltage across COUT increases.
PAGE 13
L5973D 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 14
Package mechanical data Table 6. L5973D HSOP8 mechanical data mm inch Dim Min Typ A Min Typ 1.70 Max 0.0669 A1 0.00 A2 1.25 b 0.31 0.51 0.0122 0.0201 c 0.17 0.25 0.0067 0.0098 D 4.80 4.90 5.00 0.1890 0.1929 0.1969 D1 3 3.1 3.2 0.118 0.122 0.126 E 5.80 6.00 6.20 0.2283 0.2441 E1 3.80 3.90 4.00 0.1496 0.1575 E2 2.31 2.41 2.51 0.091 e 0.10 0.00 0.0039 0.0492 0.095 0.099 1.27 h 0.25 0.50 0.0098 0.0197 L 0.40 1.27 0.0157 0.
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L5973D 8 Order code Order code Table 7.
PAGE 16
Revision history 9 L5973D Revision history pp Table 8.
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L5973D 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.