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
SO8

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 250m) 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.

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 Test application circuit
3.3V VIN = 4.4V to 35V VREF VCC SYNC. C1 10F 35V CERAMIC COMP C4 22nF C3 220pF 6 8 2 4 INH. R3 4.7K

Figure 1.

1

OUT

L1 33H D1 STPS2L40U

VOUT=3.3V

L5970D
3 7 5 GND FB

R1 5.6K

C2 100F 10V

R2 3.3K

D98IN954C

October 2007

Rev 16

1/16
www.st.com 16

Contents

L5970D

Contents
1 Pin settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 1.2 Pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2

Electrical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1 2.2 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

3 4 5 6 7 8 9

Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Typical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Application ideas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Order code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

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L5970D

Pin settings

1
1.1

Pin settings
Pin connection
Figure 2. Pin connection (top view)

OUT SYNC INH COMP

1 2 3 4
D98IN955

8 7 6 5

VCC GND VREF FB

1.2

Pin description
Table 1. Pin description
N 1 2 3 4 5 6 7 8 Type OUT SYNC INH COMP FB VREF GND VCC Regulator output. Master/slave synchronization. A logical signal (active high) disables the device. If INH not used the pin must be grounded. When it is open an internal pull-up disable the device. 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. 3.3V VREF. No cap is requested for stability. Ground. Unregulated DC input voltage. Description

3/16

Electrical data

L5970D

2
2.1

Electrical data
Maximum ratings
Table 2. Absolute maximum ratings
Symbol V8 V1 I1 V4, V5 V3 V2 PTOT TJ TSTG Input voltage Output DC voltage Output peak voltage at t = 0.1s Maximum output current Analog pins INH SYNC Power dissipation at TA 60C Operating junction temperature range Storage temperature range Parameter Value 40 -1 to 40 -5 to 40 int. limit. 4 -0.3V to VCC -0.3 to 4 0.75 -40 to 150 -55 to 150 V W C C V Unit V V V

2.2

Thermal data
Table 3. Thermal data
Symbol RthJA Parameter Maximum thermal resistance junction-ambient SO8 120 (1) Unit C/W

1. Package mounted on board

4/16

L5970D

Electrical characteristics

3

Electrical characteristics
Table 4. Electrical characteristics ( TJ = 25C, VCC = 12V, unless otherwise specified)
Symbol VCC RDS(on) Il fs Parameter Operating input voltage range Mosfet on Resistance Maximum limiting current Switching frequency 225 Duty cycle Dynamic characteristics (see test circuit ). V5 h Voltage feedback Efficiency 4.4V < VCC < 36V, 20mA < IO < 2A VO = 5V, VCC = 12V 1.220
(1)

Test condition Vo = 1.235V; Io = 2A
(1)

Min 4.4

Typ

Max 36

Unit V A KHz KHz %

(1)

0.250 1.5 1.87 250 250

0.5 2.25 280 275 100

VCC = 4.4V to 36V
(1)

212

0

1.235 1.235 90

1.25 1.272

V V %

1.198

DC characteristics Iqop Iq Total operating quiescent current Quiescent current Duty cycle = 0; VFB = 1.5V Vinh > 2.2V Iqst-by Total stand-by quiescent current VCC = 36V; Vinh > 2.2V
(1) (1)

3

5 2.5

mA mA A A

50 80

100 150

(1)

Inhibit INH threshold voltage Error amplfier VOH VOL Io source High level output voltage Low level output voltage Source output current VFB = 1V VFB = 1.5V VCOMP = 1.9V; VFB = 1V 200 300 3.5 0.4 V V A Device ON Device OFF 2.2 0.8 V V

5/16

Electrical characteristics Table 4. Electrical characteristics (continued) ( TJ = 25C, VCC = 12V, unless otherwise specified)
Symbol Io sink Ib Parameter Sink output current Source bias current DC open loop gain gm Transconductance RL = Icomp = -0.1mA to 0.1mA VCOMP = 1.9V 50 Test condition VCOMP = 1.9V; VFB = 1.5V Min 1 Typ 1.5 2.5 65 4 Max

L5970D

Unit mA A dB

2.3

mS

Sync function High input voltage Low input voltage Slave sink current Master output amplitude Output pulse width Reference section Reference voltage IREF = 0 to 5mA VCC = 4.4V to 36V Line regulation Load regulation Shor t circuit current IREF = 0mA VCC = 4.4V to 36V IREF = 0 to 5mA 10
(1)

VCC = 4.4V to 36V VCC = 4.4V to 36V Vsync = 0.74V (2) Vsync = 2.33V Isource = 3mA no load, Vsync = 1.65V

2.5

VREF 0.74

V V mA mA V s

0.11 0.21 2.75 0.20 3 0.35

0.25 0.45

3.234 3.2

3.3 3.3

3.366 3.399

V V

5

10

mV

8 18

15 30

mV mA

1. Specification Referred to TJ from -40 to 125C. Specification over the -40 to +125 TJ Temperature range are assured by design, characterization and statistical correlation. 2. Guaranteed by design.

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L5970D

Typical characteristics

4

Typical characteristics
Figure 3.
Tj(C)

Junction temperature vs output current

Figure 4.
Vo (V) 3.312

Load regulator

130 120 110 100 90 80 70 60 50 40 30 20 0.2

Vo=3.3V

Vo=2.5V

3.308 3.304 3.3 3.296 3.292 3.288 3.284 3.28 3.276

Vcc = 12V Vo = 3.3V Tj = 25C

Vcc=5V Tamb=25C

Vo=1.8V

Tj = 125C

0.4

0.6

0.8
Io(A)

1

1.2

1.4

1.6

0

0.5 Io (A)

1

1.5

Figure 5.
Tj(C)

Junction temperature vs output current

Figure 6.
Vo (V) 3.312

Line regulator

13 0 12 0 110 10 0 90 80 70 60 50 40 30 20 0. 2

V o =5 V Vc c = 1 2V Tam b=25C

Vo =3.3V

3.308 3.304 3.3 3.296 3.292 3.288 3.284 3.28 3.276

Vcc = 12V Vo = 3.3V

Tj = 25C

V o =2 . 5 V

Tj = 125C

0 .4

0 .6

0 .8
Io (A)

1

1 .2

1 .4

1 .6

0

10

20 Vcc (V)

30

40

Figure 7.

Junction temperature vs output current

Figure 8.
Vo (V) 1.25

Output voltage vs junction temperature

T j ( C )

14 0 12 0 10 0 80 60 40 20 0 0 .2
Vcc=24V Tam b=25C

Vo= 18V

Vo =12V

1.24
Vo = 5 V

1.23 1.22 Vcc = 12V 1.21 1.2 Vcc=12V

0 .4

0 .6

0 .8
Io (A )

1

1 .2

1. 4

-50

0

50 Tj (C)

100

150

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Typical characteristics

L5970D

Figure 9.
Iq (mA)

Quiescent current vs junction temperature

Figure 10. Switching frequency vs junction temperature
Fsw (KHz) 260

2

1.8

250

1.6 Vcc = 12V DC = 0%

240

1.4

230

Vcc = 12V Vo = 3.3V

1.2 -50 0 50 Tj (C) 100 150

220 -50 0 50 Tj (C) 100 150

Figure 11. Shutdown current vs junction Figure 12. Efficiency vs output current temperature
Ishd (A) 70

Vcc = 12V

Efficiency (%)

60

50

40

30 -50 0 50 Tj (C) 100 150

94 92 90 88 86 84 82 80 78 76 74 72 70 0.1

Vo=3.3V Vo=2.5V

Vo=1.8V Vcc=5V 0.2 0.3 0.4 0.5 0.6 Io (A) 0.7 0.8 0.9 1

Figure 13. Efficiency vs output current
92 90 88 86 84 82 80 78 76 74 72 70

Vo=5V Vo=3.3V

Efficiency (%)

Vo=2.5V Vcc=12V 0.1 0.2 0.3 0.4 0.5 0.6 Io (A) 0.7 0.8 0.9 1

8/16

L5970D

Application circuit

5

Application circuit
Figure 14. Demo board application circuit
VREF VCC SYNC. C1 10F 25V CERAMIC COMP C4 22nF C3 220pF

3.3V VIN = 4.4V to 25V

6 8 2 4 INH.

1

OUT

L1 33H D1 STPS2L25U

VOUT=3.3V

L5970D
3 7 5 GND FB

R1 5.6K

C2 100F 10V

R3 4.7K

R2 3.3K

D03IN1437

Table 5. Component list
Reference C1 C2 C3 C4 R1 R2 R3 D1 L1 STPS2L25U DO3316P-333 Part number GRM32DR61E106KA12L POSCAP 10TPB100M C1206C221J5GAC C1206C223K5RAC Description 10F, 25V 100F, 10V 220pF, 5%, 50V 22nF, 10%, 50V 5.6K, 1%, 0.1W 0603 3.3K, 1%, 0.1W 0603 4.7K, 1%, 0.1W 0603 2A, 25V 33H, 2A Manufacturer MURATA Sanyo KEMET KEMET Neohm Neohm Neohm STMicroelectronics COILCRAFT

9/16

Application circuit Figure 15. PCB layout (component side)

L5970D

Figure 16. PCB layout (bottom side)

Figure 17. PCB layout (front side)

10/16

L5970D

Application ideas

6

Application ideas
Figure 18. Dual output voltage with auxiliary winding
N1/N2=2 D2 1N4148 VOUT1=5V 30mA

VIN=12V

VCC

OUT

Lp=22uH
D1 STPS25L25U

8
COMP C1 10uF 25V Ceramic

1 U1 L5970D
FB

VOUT=3.3V 0.5A C4 100uF 10V C5 47uF 10V

4 2 6
GND

7

5 3
INH

C2 220pF

C3 22nF R3 4.7k

SYNC VREF

3.3V

Figure 19. Buck-boost regulator
VIN=12V VCC OUT

L1 33uH

8 U1
COMP C1 10uF 25V Ceramic
C2 10uF C3 35V Ceramic 220pF

1
D1 STPS2L25U
2.7k VOUT=-12V/0.3A

L5970 4 2 6
GND

7

5 3

FB

C4 22nF R3 4.7k

SYNC VREF

INH

24k

C5 100uF 16V

3.3V

Vin=12V Vout=-12V

Iout=0.5A Efficiency=81%

Figure 20. Positive Buck-Boost regulator
VIN=5V

L1 33uH
VCC

8 U1 L5970 4 2 6
GND

OUT

D2 STPS2L25U

VOUT=12V/0.3A

1
D1 STPS2L25U
24k

COMP C1 10uF 25V Ceramic

7

5 3

FB

C2 220pF

C3 22nF R3 4.7k

M1 STN4NE03L
2.7k

SYNC VREF

INH

C4 100uF 16V

3.3V

Vin=5V Vout=12V Iout=0.3A Efficiency=76%

Figure 21. Synchronization example
V IN VCC OU T VCC OU T

8 L5970D 4 2
SYNC VR EF

1
FB COMP

8 L5970D 4 2
SYNC VR EF

1
FB

COMP

6
GN D

7

5 3

6
GN D

7

5 3

IN H

INH

11/16

Package mechanical data

L5970D

7

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.st.com

12/16

L5970D

Package mechanical data

Table 6. SO-8 mechanical data
mm. Dim. Min A 1.35 Typ Max 1.75 Mi n 0.053 Typ Ma x 0.069 inch

A1 A2 B C
D

0.10 1.10 0.33 0.19 4.80 3.80 1.27 5.80 0.25 0.40

0.25 1.65 0.51 0.25 5.00 4.00

0.004 0.043 0.013 0.007 0.189 0.15 0.050

0.010 0.065 0.020 0.010 0.197 0.157

(1)

E e H h L k ddd

6.20 0.50 1.27

0.228 0.010 0.016

0.244 0.020 0.050

0 (min.), 8 (max.) 0.10 0.004

1. Dimensions D does not include mold flash, protru-sions or gate burrs. Mold flash, potrusions or gate burrs shall not exceed 0.15mm (.006inch) in total (both side).

Figure 22. Package dimensions

13/16

Order codes

L5970D

8

Order codes
Table 7. Order codes
Part number L5970D L5970D013TR Package SO8 SO8 Packaging Tube Tape and reel

14/16

L5970D

Revision history

9

Revision history
Table 8. Revision history
Date 26-Jan-2007 16-Mar-2007 16-Oct-2007 Revision 14 15 16 Updated Table 5 on page 9 Mechanical data typo Updated Section 5: Application circuit on page 9 Changes

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L5970D

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Document Number: 7324



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