STMicroelectronics L5970D Technical data
UP TO 1A STEP DOWN SWITCHING REGULATOR
■ 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 FEEDFO RWA R D
■ 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 MONITORS
■ NETWORKING: XDSL, MODEMS,DC-DC
MODULES
■ COMPUTER: PRINTERS, AUDIO/GRAPHIC
CARDS, OPTICAL STORAGE, HARD DISK
DRIVE
■ INDUSTRIAL: CHARGERS, CAR BATTERY
DC-DC CONVERTERS
L5970D
SO8
ORDERING NUMBERS: L5970D (Tube)
L5970D013TR (T&R)
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 mi nimize the size of the external components.
An internal oscillator fixes the switching frequency
at 250KHz.
Having a minimum inpu t vol tage 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.
TEST APPLICATION CIRCUIT
3.3V
VIN = 4.4V to 35V
C1
10µF
35V
CERAMIC
September 2003
22nF
220pF
C4
C3
VREF
VCC
SYNC.
COMP
R3
4.7K
6
8
2
4
INH.
L5970D
3
7
1
5
GND
D98IN954C
OUT
FB
L1 33µH
D1
STPS2L40U
R1
5.6K
R2
3.3K
VOUT=3.3V
C2
100µF
10V
1/10
L5970D
PINS CONNECTION (Top View)
OUT
SYNC
INH
COMP
1
2
3
4
8
7
6
5
D98IN955
VCC
GND
VREF
FB
PINS FUNCTION
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
7 GND Ground.
8V
3.3V V
REF
Unregulated DC input voltage.
CC
. No cap is requested for stability.
REF
THERMA L D ATA
Symbol Parameter Value Unit
R
th (j-amb)
(*) Package mounted on board
Thermal Resistance Junction to ambient Max. 120 (*) °C/W
ABSOLUTE MAXIMUM RATINGS
Symbol Parameter Value Unit
V
V
I
1
, V
V
4
V
V
P
tot
T
T
stg
Input Voltage 40 V
8
Output DC voltage
1
Output peak voltage at t = 0.1µs
-1 to 40
-5 to 40
Maximum output current int. limit.
Analog pins 4 V
5
INH -0.3V to V
3
SYNC -0.3 to 4 V
2
Power dissipation at T
Operating junction temperature range -40 to 150 °C
j
≤ 60°C 0.75 W
amb
Storage temperature range -55 to 150 °C
CC
V
V
2/10
L5970D
ELECTRICAL CHARACTERISTCS (Tj = 25°C, VCC = 12V, unless otherwise specified.)
(*) Specification Referred to T
Symbol Parameter Test Condition Min. Typ. Max. Unit
V
R
DSON
DYNAMIC CHARACTERISTICS (see test circuit).
DC CHARACTERISTICS
I
I
qst-by
INHIBIT
ERROR AMPLIFIER
V
V
I
o source
I
o sink
gm Transconductance I
SYNC FUNCTION
REFERENCE SECTION
Note (1): S pecification over the -40 to +125 Tj Tem perature ra nge are assured by design, characte ri zation and s tatistica l correlation.
Note (2): Guar anteed by design.
Operating input voltage
CC
range
Mosfet on Resistance * 0.250 0 .5 Ω
I
Maximum limiting current VCC = 4.4V to 36V * 1.5 1.87 2.25 A
l
fs Switching frequency * 212 250 280 KHz
Duty cycle 0 100 %
V
Voltage feedback 4.4V < VCC < 36V,
5
η Efficiency VO = 5V, VCC = 12V 90 %
Total operating quiescent
qop
current
Quiescent current Duty Cycle = 0; VFB = 1.5V 2.5 mA
I
q
Total stand-by quiescent
current
INH Threshold voltage Device ON 0.8 V
High level output voltage VFB = 1V 3.5 V
OH
Low level output voltage VFB = 1.5V 0.4 V
OL
Source output current V
Sink output current V
I
Source bias current 2.5 4 µA
b
DC open loop gain R
High Input Voltage V
Low Input Voltage V
Slave Sink Current
Master Output Amplitude I
Output Pulse Width no load, V
Reference Voltage 3.234 3.3 3.366 V
Line Regulation I
Load Regulation I
Short Circuit Current 10 18 30 mA
from -40 to +125°C (1).
j
Vo = 1.235V; Io = 1A * 4.4 36 V
20mA < IO < 1A
V
> 2.2V
inh
VCC = 36V; V
> 2.2V
inh
Device OFF 2.2 V
= 1.9V; VFB = 1V 200 300 µA
COMP
= 1.9V; VFB = 1.5V 1 1.5 mA
comp
= ∞ 50 65 dB
L
= -0.1mA to 0.1mA
comp
V
= 1.9V
comp
= 4.4V to 36V 2.5 V
CC
= 4.4V to 36V 0.74 V
CC
= 0.74V
V
sync
V
= 2.33V
sync
= 3mA 2.75 3 V
source
I
= 0 to 5mA
REF
(2)
= 1.65V 0.20 0.35 µs
sync
VCC = 4.4V to 36V
= 0mA
REF
V
= 4.4V to 36V
CC
= 0 to 5mA 8 15 mV
REF
225 250 275 KHz
1.220 1.235 1.25 V
* 1.198 1.235 1.272 V
*35mA
*
*
50
80
100
150
2.3 mS
REF
0.11
0.21
0.25
0.45
* 3.2 3.3 3.399 V
510mV
µA
µA
V
mA
mA
3/10
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