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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
SO8
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 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.
8 1 OUT L1 33H D1 STPS2L40U 7 5 FB GND R3 4.7K R2 3.3K VOUT=3.3V
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
VCC
VIN = 4.4V to 35V
C1 10F 35V CERAMIC
COMP C4 22nF C3 220pF
L5972D
4 6 2 3
R1 5.6K
C2 100F 10V
D03IN1436
October 2007
Rev 10
1/15
www.st.com 15
Contents
L5972D
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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Application ideas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Order code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
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L5972D
Pin settings
1
1.1
Pin settings
Pin connection
Figure 2. Pin connection (top view)
OUT GND GND COMP
1 2 3 4
D02IN1367
8 7 6 5
VCC GND GND FB
1.2
Pin description
Table 1.
N 1 2,3,6,7 4 5 8
Pin description
Pin OUT GND COMP FB VCC Regulator output. Ground. 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. Unregulated DC input voltage. Description
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Electrical data
L5972D
2
2.1
Electrical data
Maximum ratings
Table 2.
Symbol V8 V1 I1 V4, V5 Ptot Tj Tstg Input voltage Out pin DC voltage Out pin peak voltage at t = 0.1s Maximum output current Analog pins Power dissipation at TA 70C Operating junction temperature range Storage temperature range
Absolute maximum ratings
Parameter Value 40 -1 to 40 -5 to 40 int. limit. 4 1.2 -40 to 150 -55 to 150 V W C C Unit V V V
2.2
Thermal data
Table 3.
Symbol RthJA
Thermal data
Parameter Maximum thermal resistance junction-ambient SO8 65
(1)
Unit C/W
1. Package mounted on board
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L5972D
Electrical characteristics
3
Electrical characteristics
Table 4.
Symbol VCC RDS(on) Il fs
Electrical characteristics ( TJ = 25C, VCC = 12V, unless otherwise specified)
Parameter Operating input voltage range Mosfet on Resistance Maximum limiting current Switching frequency 225 Duty cycle 0 250 275 100 kHz % VCC = 4.4V to 36V
(1)
Test condition Vo = 1.235V; Io = 2A
(1)
Min 4.4
Typ
Max 36
Unit V A kHz
(1)
0.250 2 212 2.5 250
0.5 3 280
Dynamic characteristics (see test circuit ). V5 h Voltage feedback Efficiency 4.4V < VCC < 36V, 20mA < IO < 2A VO = 5V, VCC = 12V 1.220
(1)
1.235 1.235 90
1.25 1.272
V V %
1.198
DC characteristics Iqop Iq Error amplfier VOH VOL Io source Io sink Ib High level output voltage Low level output voltage Source output current Sink output current Source bias current DC open loop gain gm Transconductance RL = Icomp = -0.1mA to 0.1mA VCOMP = 1.9V 50 VFB = 1V VFB = 1.5V VCOMP = 1.9V; VFB = 1V VCOMP = 1.9V; VFB = 1.5V 200 1 300 1.5 2.5 65 2.3 4 3.5 0.4 V V A mA A dB mS Total operating quiescent current Quiescent current Duty cycle = 0; VFB = 1.5V
(1)
3
5 2.5
mA 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.
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Typical characteristics
L5972D
4
Typical characteristics
Figure 3.
Vo (V) 3.312 3.308 3.304 3.3 3.296 3.292 3.288 3.284 3.28 3.276 0 0.5 Io (A) 1 1.5 Tj = 125C
1.2 -50 0 50 Tj (C) 100 150 1.4
Output voltage vs. junction temperature
Figure 4.
Quiescent current vs. junction temperature
Iq (mA)
2
Vcc = 12V Vo = 3.3V Tj = 25C
1.8
1.6 Vcc = 12V DC = 0%
Figure 5.
Line regulator
Figure 6.
Ishd (A) 70
Shutdown current vs. junction temperature
Vo (V) 3.312 3.308 3.304 3.3 3.296 3.292 3.288 3.284 3.28 3.276 0 10 20 Vcc (V) 30 40 Tj = 125C Vcc = 12V Vo = 3.3V Tj = 25C
60
Vcc = 12V
50
40
30 -50 0 50 Tj (C) 100 150
Figure 7.
Vo (V) 1.25 1.24 1.23
Output voltage vs. junction temperature
Figure 8.
Iq (mA)
Switching frequency vs. junction temperature
2
1.8
1.6
1.22 Vcc = 12V 1.21 1.2 -50 0 50 Tj (C) 100 150 Vcc=12V
1.2 -50 1.4
Vcc = 12V DC = 0%
0
50 Tj (C)
100
150
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L5972D
Application circuit
5
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
VIN = 4.4V to 25V
VCC
8
1
OUT
L1 33H D1 STPS2L25U
VOUT=3.3V
C1 10F 25V CERAMIC
COMP C4 22nF C3 220pF R3 4.7K
L5972D
4 6 2 3 7 5 FB GND
R1 5.6K
C2 100F 10V
R2 3.3K
D03IN1438
Table 5.
Component list
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 STPS2L25U DO3316P-333 2A, 25V 33H, 2.1A Manufacturer MURATA Sanyo KEMET KEMET Neohm Neohm Neohm ST COILCRAFT
Reference C1 C2 C3 C4 R1 R2 R3 D1 L1
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Application circuit Figure 10. PCB layout (component side)
L5972D
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
TJ(C) 100.0 90.0 80.0 70.0 60.0 50.0 40.0 30.0 20.0 0.2 0.4 0.6 0.8 1 1.2 Io(A) 1.4 1.6 1.8 2
Figure 14. Efficiency vs output current
95 93 91
Vo=3.3V
Vin=5V Tamb.=25 C
Vo=2.5V
Vo=3.3V
Efficiency (%)
89 87 85 83 81 79 77 75 73 71 69 67 0.1 0.3 0.5 0.7 0.9 1.1 1.3 1.5 1.7
Vo=2.5V
Vo=1.8V
Vo=1.8V
Vin=5V
Io (A)
Figure 15. Junction temperature vs output current
TJ(C) 100.0 90.0 80.0 70.0 60.0 50.0 40.0 30.0 20.0 0.2 0.4 0.6 0.8 1 1.2 Io(A) 1.4 1.6 1.8 2 Vo=2.5V Vin=12V Tamb= 25C Vo=5V Vo=3.3V
Figure 16. Efficiency vs output current
96 94 92 90 88 Efficiency (%) 86 84 82 80 78 76 74 72 70 0.1 0.3 0.5 0.7 0.9 Io (A) 1.1 1.3 1.5 1.7 Vin=12V Vo=2.5V Vo=3.3V Vo=5V
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Application ideas
L5972D
6
Application ideas
Figure 17. Positive buck-boost regulator
VIN=5V Vcc OUT
L1 33uH
D2 STPS2L25U
VOUT=12V/0.45A
8
COMP C1 10uF 10V Ceramic
1 L5972D
FB D1 STPS2L25U 24k
4 2
C2 220pF C3 22nF R3 4.7k
6
GND
7
5 3
M1 STN4NE03L
2.7k
C4 100uF 16V
Figure 18. Buck-boost regulator
VIN=5V Vcc OUT
L1 33uH
8
COMP C1 10uF 10V Ceramic
1 L5972D
FB D1 STPS2L25U 2.7k
C2 10uF C3 25V Ceramic 220pF
4 2
C4 22nF R3 4.7k
VOUT=-12V/0.45A
6
GND
7
5 3
24k
C5 100uF 16V
Figure 19. Dual output voltage with auxiliary winding
n=N1/N2=2 D2 N2 STPS2L25U VIN=12V Vcc OUT VOUT1=5V 50mA
8
COMP C1 10uF 25V
1 L5972D
FB
N1 D1 STPS2L25U
VOUT=3.3V
4 2
C2 220pF C3 22nF R3 4.7k
6
GND
7
5 3
C4 100uF 10V
C5 47uF 10V
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L5972D
Package mechanical data
7
Package mechanical data
In order to meet environmental requirements, ST offers these devices in ECOPACK(R) 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
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Package mechanical data
L5972D
Table 6.
Dim.
SO-8 Mechanical data
mm. Min Typ Max 1.75 Min 0.053 inch Typ Max 0.069
A
1.35
A1 A2 B C
D (1)
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
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 20. Package dimensions
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L5972D
Order codes
8
Order codes
Table 7. Order codes
Part number L5972D L5972D013TR Package SO8 SO8 Packaging Tube Tape and reel
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Revision history
L5972D
9
Revision history
Table 8.
Date 02-Feb-2007 10-Apr-2007 16-Oct-2007
Revision history
Revision 8 9 10 Updated Table 5 on page 7 Mechanical data typo Updated Section 5: Application circuit on page 7 Changes
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L5972D
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