1/10
L5970D
May 2003
■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 FEEDFOR WA RD
■ZERO LOAD CURRENT OPERATION
■INTERNAL CURRENT LIMITING
■INHIBIT FOR ZERO CURRENT
CONSUMPTION
■SINCHRONIZATION
■PROTECTION AGAINST FEEDBACK
DISCONNECTION
■THERMAL SHUTDOWN
APPLICATIONS:
■CONSUMER: STB, DVD, TV, VCR,CAR
RADIO, LCD MONITOR S
■NETWORKING: XDSL, MODEMS,DC-DC
MODULES
■COMPUTER: PRINTERS, AUDIO/GR APHI C
CARDS, OPTICAL STORAGE, HARD DISK
DRIVE
■INDUSTRIAL : CHARGERS, CAR BATTERY
DC-DC CONVERTERS
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 ex-
ternal components.
An internal oscillator fixes the switching frequency
at 250KHz.
Having a m inim um inpu t voltag e of 4.4V only, it is
particularly suitable for 5V bus, available in all
computer related applica tions.
Pulse by pulse current limit with the internal fre-
quency modulation offers an effective constant
current short circuit protection.
SO8
ORDERING NUMBERS: L5970D (SO8)
L5970D013TR (T&R)
UP TO 1A STEP DOWN SWITCHING REGULATOR
TEST APPLICATION CIRCUIT
D98IN954C
8
2
45
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
L5970D
2/10
PINS CONNECTION (Top View)
PINS FUNCTION
THE RMAL D A TA
(*) Package mounted on board
ABSOLUTE MAXIMUM RATINGS
N. Name Description
1 OUT Regulator Output.
2 SYNC Master/slave synchronization.
3 INH 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.
5 FB 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.
6V
REF
3.3V V
REF
. No cap is requested for stability.
7 GND Ground.
8V
CC
Unregulated DC input voltage.
Symbol Parameter Value Unit
R
th (j-amb)
Thermal Resistance Junction to ambient Max. 120 (*) °C/W
Symbol Parameter Value Unit
V
8
Input Voltage 40 V
V
1
Output DC voltage
Output peak voltage at t = 0.1µs-1 to 40
-5 to 40 V
V
I
1
Maximum output current int. limit.
V
4
, V
5
Analog pins 4 V
V
3
INH -0.3V to V
CC
V
2
SYNC -0.3 to 4 V
P
tot
Power dissipation at T
amb
≤ 60°C 0.75 W
T
j
Operating junction temperature range -40 to 150 °C
T
stg
Storage temperature range -55 to 150 °C
OUT
SYNC
INH
COMP
1
3
2
4
VCC
VREF
GND
FB
8
7
6
5
D98IN955
3/10
L5970D
ELECTRICAL CHARACTE RISTCS (Tj = 25°C, V
CC
= 12V, un less otherwise specif ied.)
(*) Specification Referred to T
j
from -40 to +125°C (1).
Note (1): S pecif i catio n over the -40 to +125 Tj Te m perat ure ra nge are assured by desi gn, charac te ri zati on and s tatist i cal cor relation.
N ote (2 ): Gu aran t e ed by design.
Symbol Parameter Test Condition Min. Typ. Max. Unit
V
CC
Operating input voltage
range V
o
= 1.235V; I
o
= 1A * 4.4 36 V
V
d
Dropout voltage V
CC
= 4.4V; I
o
= 1A * 0.25 0.5 V
I
l
Maximum limiting current V
CC
= 4.4V to 36V * 1.5 1.87 2.25 A
fs Switching frequency * 212 250 280 KHz
225 250 275 KHz
Duty cycle 0 100 %
DYNAMIC CHARACTERISTICS (see test circuit fig. xx note 1).
V
5
Voltage feedback 4.4V < V
CC
< 36V,
20mA < I
O
< 1A 1.220 1.235 1.25 V
* 1.198 1.235 1.272 V
ηEfficiency V
O
= 5V, V
CC
= 12V 90 %
DC CHARACTERISTICS
I
qop
Total operating quiescent
current *35mA
I
q
Quiescent current Duty Cycle = 0; VFB = 1.5V 2.5 mA
I
qst-by
Total stand-by quiescent
current V
inh
> 2.2V
V
CC
= 36V; V
inh
> 2.2V *
*50
80 100
150 µA
µA
INHIBIT INH Threshold voltage Device ON 0.8 V
Device OFF 2.2 V
ERROR AMPLIFIER
V
OH
High level output voltage V
FB
= 1V 3.5 V
V
OL
Low level output voltage V
FB
= 1.5V 0.4 V
I
o so urce
Source output current V
COMP
= 1.9V; V
FB
= 1V 200 300 µA
I
o sink
Sink output current V
comp
= 1.9V; V
FB
= 1.5V 1 1.5 mA
I
b
Source bias current 2.5 4 µA
DC open loop gain R
L
= ∞50 65 dB
gm Transconductance I
comp
= -0.1mA to 0.1mA
V
comp
= 1.9V 2.3 mS
SYNC FUNCTION
High Input Voltage V
CC
= 4.4V to 36V 2.5 V
REF
V
Low Input Voltage V
CC
= 4.4V to 36V 0.74 V
Slave Sink Current V
sync
= 0.74V
(2)
V
sync
= 2.33V 0.11
0.21 0.25
0.45 mA
mA
Master Output Amplitude I
source
= 3mA 2.75 3 V
Output Pulse Width no load, V
sync
= 1.65V 0.20 0.35 µs
REFERENCE SECTION
Reference Voltage 3.234 3.3 3.366 V
I
REF
= 0 to 5mA
V
CC
= 4.4V to 36V * 3.2 3.3 3.399 V
Line Regulation I
REF
= 0mA
V
CC
= 4.4V to 36V 510mV
Load Regulation I
REF
= 0 to 5mA 8 15 mV
Short Circuit Current 10 8 30 mA
L5970D
4/10
Figure 1. Junction Te mperatu re vs. Outpu t
Current (SO8) *)
Figure 2. Junction Te mperatu re vs. Outpu t
Current (SO8) *)
Figure 3. Junction Te mperatu re vs. Outpu t
Current (SO8) *)
Figu re 4. Lo a d Re g ul a tio n
Figu re 5. Li ne R egula tio n
Figu re 6. Ou tput V ol ta ge vs . Junction
Temperature
*) Package mount ed on demoboard
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
20
30
40
50
60
70
80
90
100
110
120
130
0.20.40.60.8 1 1.21.41.6
Io(A)
Tj(°C)
Vo=5V
Vo=2.5V
Vo=3.3V
Vcc=12V
Tamb=25°C
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
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
3.276
3.28
3.284
3.288
3.292
3.296
3.3
3.304
3.308
3.312
010203040
Vcc (V)
Tj = 125°C
Tj = 25°C
Vcc = 12V
Vo = 3.3V
Vo (V)
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
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L5970D
Figure 7. Quiescent Current vs. Junction
Temperature
Figu re 8. Shut d own Current v s. Junctio n
Temperature
Figure 9. Switching Frequency vs.Junction
Temperature
1.2
1.4
1.6
1.8
2
-50 050
100 150
Tj (°C)
Iq ( mA )
Vcc = 12V
DC = 0%
30
40
50
60
70
-50 050 100 150
Ishd (µA)
Vcc = 12V
Tj (°C)
220
230
240
250
260
-50 0 50 100 150
Tj (C)
Fsw (KHz)
Vcc = 12V
Vo = 3.3V
L5970D
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Figure 10. Demoboard schematic
Part list de m oboard
Reference Part Number Description Manufacturer
C1 10µF, 25V TOKIN
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
45
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
Figure 11. Eff iciency vs. Output Current Figure 12. Efficiency vs. Output Current
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
7/10
L5970D
Figu re 13 . PC B layo ut ( com pon ent sid e )
Figure 14. PCB layout (bottom side)
Figu re 15 . PC B layo ut ( front side)
42mm
34mm
L5970D
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APPLICATI ON IDEAS
Figu re 16. Dual ou tput vol ta g e with aux ili ary wi nd in g
Figure 17. Buck-Boost regulator
Figure 18. Positive Buck-Boost regul
Figu re 19 . Sy nchro ni za tion exa m pl e
VIN=12V
C1
10uF
25V
Ceramic
D1
STPS25L25U
VCC
COMP
GND
OUT
FB
INH
SYNC VREF
L5970D
1
3
75
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
75
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 = -12 V Iout=0.5A Efficiency=8 1%
VIN=5V
C1
10uF
25V
Ceramic
D1
STPS2L25U
VCC
COMP
GND
OUT
FB
INH
SYNC VREF
L5970
1
3
75
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
75
6
4
8
2
L5970D
COMP
VCC
GND
OUT
FB
INH
SYNC VREF
1
3
75
6
4
8
2
L5970D
COMP
VIN
9/10
L5970D
DIM. mm inch
MIN. TYP. MAX. MIN. TYP. MAX.
A 1.75 0.069
a1 0.1 0.25 0.004 0.010
a2 1.65 0.065
a3 0.65 0.85 0.026 0.033
b 0.35 0.48 0.014 0.019
b1 0.19 0.25 0.007 0.010
C 0.25 0.5 0.010 0.020
c1 45° (typ.)
D (1) 4.8 5.0 0.189 0.197
E 5.8 6.2 0.228 0.244
e 1.27 0.050
e3 3.81 0.150
F (1) 3.8 4.0 0.15 0.157
L 0.4 1.27 0.016 0.050
M 0.6 0.024
S8° (max.)
(1) D and F do not include mold flash or protrusions. Mold flash or
potrusions shall not exceed 0.15mm (.006inch).
SO8
OUTLINE AND
MECHANICAL DATA
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of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is gra nt ed
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to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products are not
authoriz ed for use as critica l com ponents in l i fe support device s or system s wit hout express written ap proval of STMicroelectr o nics.
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L5970D
