L5973D
2.5 A switch step down switching regulator
Features
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2.5 A internal switch
Operating input voltage from 4 V to 36 V
3.3 V / (±2%) reference voltage
Output voltage adjustable from 1.235 V to 35 V
Low dropout operation: 100 % duty cycle
250 kHz internally fixed frequency
Voltage feedforward
Zero load current operation
Internal current limiting
Inhibit for zero current consumption
Synchronization
Protection against feedback disconnection
Thermal shutdown
HSOP8 exposed pad
Description
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 mΩ) 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.
Applications
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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
VIN = 4.4V to 35V
VREF
VCC
SYNC.
C1
10µF
35V
CERAMIC
COMP
C4
22nF
C3
220pF
R3
4.7K
6
8
2
4
INH
1
OUT
L1 15µH
D1
STPS340U
5
FB
GND
R2
3.3K
VOUT=3.3V
L5973D
3
7
R1
5.6K
C2
330µF
10V
D03IN1439
January 2008
Rev 16
1/17
www.st.com
17
Contents
L5973D
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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Order code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2/17
L5973D
Pin settings
1
1.1
Pin settings
Pin connection
Figure 2.
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.
N°
1
2
3
4
5
6
7
8
Pin description
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 1.23 V. An external resistive divider is required for higher
output voltages.
3.3 V V
REF
. No cap is requested for stability.
Ground.
Unregulated DC input voltage.
Description
3/17
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