October 2007 Rev 16 1/16
16
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
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 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 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
D98IN954C
8
2
4
5
1
7
L5970D
C1
10µF
35V
CERAMIC
C2
100µF
10V
VOUT=3.3V
VIN = 4.4V to 35V
R1
5.6K
R2
3.3K
R3
4.7K
C4
22nF
C3
220pF
3
6
D1
STPS2L40U
3.3V
INH.
SYNC.
COMP
VCC
VREF OUT
FB
GND
L1 33µH
Contents L5970D
2/16
Contents
1 Pin settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2 Electrical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2 Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4 Typical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5 Application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
6 Application ideas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
7 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
8 Order code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
9 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
L5970D Pin settings
3/16
1 Pin settings
1.1 Pin connection
Figure 2. Pin connection (top view)
1.2 Pin description
OUT
SYNC
INH
COMP
1
3
2
4
VCC
VREF
GND
FB
8
7
6
5
D98IN955
Table 1. Pin description
N° Type Description
1 OUT Regulator output.
2 SYNC Master/slave synchronization.
3INH
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.
4 COMP E/A output for frequency compensation.
5FB
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.
6VREF
3.3V VREF
. No cap is requested for stability.
7 GND Ground.
8 VCC Unregulated DC input voltage.
Electrical data L5970D
4/16
2 Electrical data
2.1 Maximum ratings
2.2 Thermal data
Table 2. Absolute maximum ratings
Symbol Parameter Value Unit
V8Input voltage 40 V
V1Output DC voltage
Output peak voltage at t = 0.1µs
-1 to 40
-5 to 40
V
V
I1Maximum output current int. limit.
V4, V5Analog pins 4 V
V3INH -0.3V to VCC
V2SYNC -0.3 to 4 V
PTOT Power dissipation at TA ≤ 60°C 0.75 W
TJOperating junction temperature range -40 to 150 °C
TSTG Storage temperature range -55 to 150 °C
Table 3. Thermal data
Symbol Parameter SO8 Unit
RthJA Maximum thermal resistance junction-ambient 120 (1)
1. Package mounted on board
°C/W
L5970D Electrical characteristics
5/16
3 Electrical characteristics
Table 4. Electrical characteristics
( T
J
= 25°C, V
CC
= 12V, unless otherwise specified)
Symbol Parameter Test condition Min Typ Max Unit
VCC Operating input
voltage range Vo = 1.235V; Io = 2A (1) 4.4 36 V
RDS(on) Mosfet on
Resistance (1) 0.250 0.5 Ω
IlMaximum limiting
current VCC = 4.4V to 36V 1.5 1.87 2.25 A
fsSwitching frequency
(1) 212 250 280 KHz
225 250 275 KHz
Duty cycle 0 100 %
Dynamic characteristics (see test circuit ).
V5Voltage feedback 4.4V < VCC < 36V,
20mA < IO < 2A
1.220 1.235 1.25 V
(1) 1.198 1.235 1.272 V
h Efficiency VO = 5V, VCC = 12V 90 %
DC characteristics
Iqop Total operating
quiescent current (1) 35mA
IqQuiescent current Duty cycle = 0;
VFB = 1.5V 2.5 mA
Iqst-by Total stand-by
quiescent current
Vinh > 2.2V (1) 50 100 µA
VCC = 36V;
Vinh > 2.2V (1) 80 150 µA
Inhibit
INH threshold
voltage
Device ON 0.8 V
Device OFF 2.2 V
Error amplfier
VOH High level output
voltage VFB = 1V 3.5 V
VOL Low level output
voltage VFB = 1.5V 0.4 V
Io source Source output
current
VCOMP = 1.9V;
VFB = 1V 200 300 µA
Electrical characteristics L5970D
6/16
Io sink Sink output current VCOMP = 1.9V;
VFB = 1.5V 11.5 mA
IbSource bias current 2.5 4 µA
DC open loop gain RL = ∞50 65 dB
gm Transconductance
Icomp = -0.1mA to
0.1mA
VCOMP = 1.9V
2.3 mS
Sync function
High input voltage VCC = 4.4V to 36V 2.5 VREF V
Low input voltage VCC = 4.4V to 36V 0.74 V
Slave sink current Vsync = 0.74V (2)
Vsync = 2.33V
0.11
0.21
0.25
0.45
mA
mA
Master output
amplitude Isource = 3mA 2.75 3 V
Output pulse width no load,
Vsync = 1.65V
0.20 0.35 µs
Reference section
Reference voltage 3.234 3.3 3.366 V
IREF = 0 to 5mA
VCC = 4.4V to 36V
(1) 3.2 3.3 3.399 V
Line regulation IREF = 0mA
VCC = 4.4V to 36V
510mV
Load regulation IREF = 0 to 5mA 8 15 mV
Short circuit current 10 18 30 mA
1. Specification Referred to TJ from -40 to 125°C. Specification over the -40 to +125 TJ Temperature range
are assured by design, characterization and statistical correlation.
2. Guaranteed by design.
Table 4. Electrical characteristics
(continued)
( T
J
= 25°C, V
CC
= 12V, unless otherwise specified)
Symbol Parameter Test condition Min Typ Max Unit
L5970D Typical characteristics
7/16
4 Typical characteristics
Figure 3. Junction temperature vs
output current
Figure 4. Load regulator
Figure 5. Junction temperature vs
output current
Figure 6. Line regulator
Figure 7. Junction temperature vs
output current
Figure 8. Output voltage vs junction
temperature
20
30
40
50
60
70
80
90
100
110
120
130
0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
Io(A)
Tj(°C)
Vo=3.3V Vo=2.5V
Vo=1.8V
Vcc=5V
Tamb=25°C
3.276
3.28
3.284
3.288
3.292
3.296
3.3
3.304
3.308
3.312
00.511.5
Io (A)
Vo (V)
Tj = 125°C
Tj = 25°C
Vcc = 12V
Vo = 3.3V
20
30
40
50
60
70
80
90
100
110
120
130
0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
Io(A)
Tj(°C)
Vo=5V
Vo=2.5V
Vo=3.3V
Vcc=12V
Ta m b =2 5 ° C
3.276
3.28
3.284
3.288
3.292
3.296
3.3
3.304
3.308
3.312
01020304
0
Vcc (V)
Tj = 125°C
Tj = 25°C
Vcc = 12V
Vo = 3.3V
Vo (V)
0
20
40
60
80
100
120
140
0.2 0.4 0.6 0.8 1 1.2 1.4
Io(A)
Tj(°C)
Vo=18V Vo=12V
Vo=5V
Vcc=24V
Tamb=25°C
Tj (°C)
Vcc=12V
1.2
1.21
1.22
1.23
1.24
1.25
-50 0 50 100 150
Vo (V)
Vcc = 12V
Typical characteristics L5970D
8/16
Figure 9. Quiescent current vs
junction temperature
Figure 10. Switching frequency vs
junction temperature
Figure 11. Shutdown current vs junction
temperature
Figure 12. Efficiency vs output current
Figure 13. Efficiency vs output current
1.2
1.4
1.6
1.8
2
-50 050
100 150
Tj (°C)
Iq (mA)
Vcc = 12V
DC = 0%
220
230
240
250
260
-50 0 50 100 150
Tj (C)
Fsw (KHz)
Vcc = 12V
Vo = 3.3V
30
40
50
60
70
-50 050 100 150
Ishd (µA)
Vcc = 12V
Tj (°C)
70
72
74
76
78
80
82
84
86
88
90
92
94
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Io (A)
Efficiency (%)
Vo=3.3V
Vo=2.5V
Vo=1.8V
Vcc=5V
70
72
74
76
78
80
82
84
86
88
90
92
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Io (A)
Efficiency (%)
Vcc=12V
Vo=5V
Vo=3.3V
Vo=2.5V
L5970D Application circuit
9/16
5 Application circuit
Figure 14. Demo board application circuit
Table 5. Component list
Reference Part number Description Manufacturer
C1 GRM32DR61E106KA12L 10µF, 25V MURATA
C2 POSCAP 10TPB100M 100µF, 10V Sanyo
C3 C1206C221J5GAC 220pF, 5%, 50V KEMET
C4 C1206C223K5RAC 22nF, 10%, 50V KEMET
R1 5.6K, 1%, 0.1W 0603 Neohm
R2 3.3K, 1%, 0.1W 0603 Neohm
R3 4.7K, 1%, 0.1W 0603 Neohm
D1 STPS2L25U 2A, 25V STMicroelectronics
L1 DO3316P-333 33µH, 2A COILCRAFT
D03IN1437
8
2
4
5
1
7
L5970D
C1
10µF
25V
CERAMIC
C2
100µF
10V
VOUT=3.3V
VIN = 4.4V to 25V
R1
5.6K
R2
3.3K
R3
4.7K
C4
22nF
C3
220pF
3
6
D1
STPS2L25U
3.3V
INH.
SYNC.
COMP
VCC
VREF OUT
FB
GND
L1 33µH
Application circuit L5970D
10/16
Figure 15. PCB layout (component side)
Figure 16. PCB layout (bottom side)
Figure 17. PCB layout (front side)
L5970D Application ideas
11/16
6 Application ideas
Figure 18. Dual output voltage with auxiliary winding
Figure 19. Buck-boost regulator
Figure 20. Positive Buck-Boost regulator
Figure 21. Synchronization example
VIN=12V
C1
10uF
25V
Ceramic
D1
STPS25L25U
VCC
COMP
GND
OUT
FB
INH
SYNC VREF
L5970D
1
3
7
5
6
4
8
2
R3
4.7k
U1
C3
22nF
3.3V
VOUT=3.3V
0.5A
C2
220pF
VOUT1=5V
30mA
C5
47uF
10V
Lp=22uH
D2
1N4148
C4
100uF
10V
N1/N2=2
VIN=12V
C1
10uF
25V
Ceramic
D1
STPS2L25U
VCC
COMP
GND
OUT
FB
INH
SYNC VREF
1
3
7
5
6
4
8
2
R3
4.7k
U1
L1
33uH
2.7k
24k
C4
22nF
3.3V
C5
100uF
16V
L5970
VOUT=-12V/0.3A
C3
220pF
C2
10uF
35V
Ceramic
Vin=12V Vout=-12V Iout=0.5A Efficiency=81%
VIN=5V
C1
10uF
25V
Ceramic
D1
STPS2L25U
VCC
COMP
GND
OUT
FB
INH
SYNC VREF
L5970
1
3
7
5
6
4
8
2
R3
4.7k
U1
L1
33uH
24k
2.7k
C3
22nF
3.3V
C4
100uF
16V
VOUT=12V/0.3A
C2
220pF
D2
STPS2L25U
M1
STN4NE03L
Vin=5V Vout=12V Iout=0.3A Efficiency=76%
VCC
GND
OUT
FB
INH
SYNC VREF
1
3
7
5
6
4
8
2
L5970D
COMP
VCC
GND
OUT
FB
INH
SYNC VREF
1
3
7
5
6
4
8
2
L5970D
COMP
VIN
Package mechanical data L5970D
12/16
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
L5970D Package mechanical data
13/16
Table 6. SO-8 mechanical data
Dim.
mm. inch
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)
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).
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 0° (min.), 8° (max.)
ddd 0.10 0.004
Figure 22. Package dimensions
Order codes L5970D
14/16
8 Order codes
Table 7. Order codes
Part number Package Packaging
L5970D SO8 Tube
L5970D013TR SO8 Tape and reel
L5970D
16/16
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