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2.5 A switch step down switching regulator
L5973D
2.5 A switch step down switching regulator
Features
■
2.5 A internal switch
■
Operating input voltage from 4 V to 36 V
■
3.3 V / (±2%) reference voltage
HSOP8 exposed pad
■
Output voltage adjustable from 1.235 V to 35 V
■
Low dropout operation: 100 % duty cycle
Description
■
250 kHz internally fixed frequency
■
Voltage feedforward
The L5973D is a step down monolithic power
switching regulator with a minimum switch current
limit of 2.5 A so it is able to deliver more than 2 A
DC current to the load depending on the
application conditions.
The output voltage can be set from 1.235 V to
35 V. The high current level is also achieved
thanks to an SO8 package with exposed frame,
that allows to reduce the Rth(j-amb) down to
approximately 40 °C/W.
The device uses an internal P-channel D-MOS
transistor (with a typical Rdson of 250 m Ω ) as
switching element to minimize the size of the
external components.
An internal oscillator fixes the switching frequency
at 250 kHz.
Having a minimum input voltage of 4 V only, it is
particularly suitable for 5 V 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.
■
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
3.3V
V REF
L1 15
µ
H
V OUT=3.3V
6
OUT
1
VIN = 4.4V to 35V
VCC
8
D1
STPS340U
L5973D
R1
5.6K
SYNC.
2
C2
330
C1
10
COMP
4
3
7
5
FB
µ
F
10V
F
35V
CERAMIC
µ
C4
22nF
INH
GND
R2
3.3K
C3
220pF
R3
4.7K
D03IN1439
January 2008
Rev 16
1/17
17
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Contents
L5973D
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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
8
Order code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
9
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2/17
647858844.047.png
L5973D
Pin settings
1
Pin settings
1.1
Pin connection
Figure 2. Pin connection (top view)
OUT
1
8
VCC
SYNC
2
7
GND
INH
3
6
VREF
COMP
4
5
FB
D98IN955
1.2
Pin description
Table 1.
Pin description
N°
Type
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 1.23 V. An external resistive divider is required for higher
output voltages.
6
VREF
3.3 V V REF . No cap is requested for stability.
7
GND
Ground.
8
VCC
Unregulated DC input voltage.
3/17
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Electrical data
L5973D
2
Electrical data
2.1
Maximum ratings
Table 2.
Absolute maximum ratings
Symbol
Parameter
Value
Unit
V 8
Input voltage
40
V
V 1
Output DC voltage
Output peak voltage at t = 0.1 µ s
-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
-0.3 V to V CC
V 2
SYNC
-0.3 to 4
V
P TOT
Power dissipation at T A ≤ 60 °C
2.25
W
T J
Operating junction temperature range
-40 to 150
°C
T STG
Storage temperature range
-55 to 150
°C
2.2
Thermal data
Table 3.
Thermal data
Symbol
Parameter
HSOP8
Exposed Pad
Unit
R thJA
Maximum thermal resistance junction-ambient
40 (1)
° C/W
1. Package mounted on board
4/17
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L5973D
Electrical characteristics
3
Electrical characteristics
Table 4.
Electrical characteristics
( T J = 25 °C, V CC = 12 V, unless otherwise specified)
Symbol
Parameter
Test condition
Min
Typ
Max Unit
V CC
Operating input
voltage range
V o = 1.235 V; I o = 2 A
(1)
4
36
V
R DS(on)
Mosfet on
Resistance
(1)
0.250 0.5
Ω
I l
Maximum limiting
current
V CC = 4.4 V to 36 V
2.5
3
3.5
A
(1)
212
250
280
kHz
f s
Switching frequency
225
250
275
kHz
Duty cycle
0
100
%
Dynamic characteristics (see test circuit ).
4.4 V < V CC < 36 V,
20 mA < I O < 2 A
1.220 1.235 1.25
V
V 5
Voltage feedback
(1)
1.198 1.235 1.272
V
h
Efficiency
V O = 5 V, V CC = 12 V
90
%
DC characteristics
I qop
Total operating
quiescent current
(1)
3
5
A
I q
Quiescent current
Duty Cycle = 0;
V FB = 1.5 V
2.5
mA
V inh > 2.2 V
(1)
50
100
µ A
Total stand-by
quiescent current
I qst-by
V CC = 36 V;
V inh > 2.2 V
(1)
80
150
µ A
Inhibit
INH threshold
voltage
Device ON
0.8
V
Device OFF
2.2
V
Error amplfier
V OH
High level output
voltage
VFB = 1 V
3.5
V
V OL
Low level output
voltage
VFB = 1.5 V
0.4
V
I o source
Source output
current
V COMP = 1.9 V;
V FB = 1 V
200
300
µ A
I o sink
Sink output current
V COMP = 1.9 V;
V FB = 1.5 V
1
1.5
A
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