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L5970D
Up to 1A step down switching regulator
General 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 1 OUT L1 33H D1 STPS2L40U 5 GND FB VOUT=3.3V
L5970D
3 7
R1 5.6K
C2 100F 10V
R2 3.3K
D98IN954C
January 2007
Rev 14
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 1. 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
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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
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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 Io sink High level output voltage Low level output voltage Source output current Sink output current VFB = 1V VFB = 1.5V VCOMP = 1.9V; VFB = 1V VCOMP = 1.9V; VFB = 1.5V 200 300 3.5 0.4 V V A Device ON Device OFF 2.2 0.8 V V
1
1.5
mA
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Electrical characteristics Table 4. Electrical characteristics ( TJ = 25C, VCC = 12V, unless otherwise specified)
Symbol Ib Parameter Source bias current DC open loop gain gm Transconductance RL = Icomp = -0.1mA to 0.1mA VCOMP = 1.9V 50 Test condition Min Typ 2.5 65 Max 4
L5970D
Unit 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 Short 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 2.
Tj(C)
Junction temperature vs. output current
Figure 3.
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 4.
Tj(C)
Junction temperature vs. output current
Figure 5.
Vo (V) 3.312
Line regulator
130 120 110 100 90 80 70 60 50 40 30 20 0.2
Vo=5V Vcc=12V Tamb=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
Vo=2.5V
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 6.
Junction temperature vs. output current
Figure 7.
Vo (V) 1.25
Output voltage vs. junction temperature
Tj(C)
140 120 100 80 60 40 20 0 0.2
Vcc=24V Tam b=25C
Vo=18V
Vo=12V
1.24
Vo=5V
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 8.
Iq (mA)
Quiescent current vs. junction temperature
Figure 9.
Fsw (KHz) 260
Switching frequency vs. junction temperature
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 10. Shutdown current vs.junction Figure 11. 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 12. 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
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L5970D
Application circuit
5
Application circuit
Figure 13. 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 C3225X5R1E106M 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 TDK Sanyo KEMET KEMET Neohm Neohm Neohm STMicroelectronics COILCRAFT
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Application circuit Figure 14. PCB layout (component side)
L5970D
42mm
34mm
Figure 15. PCB layout (bottom side)
Figure 16. PCB layout (front side)
10/16
L5970D
Application ideas
6
Application ideas
Figure 17. 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 18. 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 19. 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 20. Synchronization example
VIN VCC OUT VCC OUT
8 L5970D 4 2
SYNC VREF
1
FB COMP
8 L5970D 4 2
SYNC VREF
1
FB
COMP
6
GND
7
5 3
6
GND
7
5 3
INH
INH
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Package mechanical data
L5970D
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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L5970D
Package mechanical data
Table 6. MSOP8 Mechanical data
mm. Dim. Min A A1 A2 b c D (1) E E1 (1) e L L1 k aaa 0.400 0.050 0.750 0.250 0.130 2.900 4.650 2.900 3.000 4.900 3.000 0.650 0.550 0.950 0 (min.) 6 (max.) 0.100 0.004 0.700 0.016 0.850 Typ Max 1.10 0.150 0.950 0.400 0.230 3.100 5.150 3.100 0.002 0.03 0.010 0.005 0.114 0.183 0.114 0.118 0.193 0.118 0.026 0.022 0.037 0.028 0.033 Min Typ Max 0.043 0.006 0.037 0.016 0.009 0.122 0.20 0.122 inch
1. D and F does not include mold flash or protrusions. Mold flash or potrusions shall not exceed 0.15mm (.006inch) per side.
Figure 21. Package dimensions
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Order code
L5970D
8
Order code
Table 7. Order code
Part number L5970D L5970D013TR Package SO8 SO8 Packaging Tube Tape and reel
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L5970D
Revision history
9
Revision history
Table 8. Revision history
Date 26-Jan-2007 Revision 14 Updated Table 5 on page 9 Changes
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L5970D
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