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L5973ADTR

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P22
November 2009 Doc ID 9552 Rev 9 1/22
22
L5973AD
2 A switch step down switching regulator
Features
■ 2 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
■ 500 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
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
Description
The L5973AD is a step down monolithic power
switching regulator with a switch current limit of
2 A so it is able to deliver more than 1.5 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 R
thJA
down to
approximately 40 °C/W.
The device uses an internal P-Channel D-MOS
transistor (with a typical of 200 mΩ) as switching
element to avoid the use of bootstrap capacitor
and guarantee high efficiency.
An internal oscillator fixes the switching frequency
at 500 kHz to minimize the size of external
components.
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.
HSOP8 exposed pad
Figure 1. Test application circuit
D03IN1453
8
4
5
1
7
L5973AD
C1
10μF
35V
CERAMIC
C2
330μF
10V
VOUT=3.3V
VIN = 4V to 35V
R1
5.6K
R2
3.3K
R3
4.7K
C4
22nF
C3
220pF
3
L1 15μH
D1
STPS340U
COMP
VCC
OUT
FB
GNDINH
2
6
3.3V
SYNC.
VREF
www.st.com
Contents L5973AD
2/22 Doc ID 9552 Rev 9
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 Functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.1 Power supply and voltage reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.2 Voltages monitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.3 Oscillator and synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.4 Current protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.5 Error amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.6 PWM comparator and power stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
4.7 Inhibit function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
4.8 Thermal shutdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5 Additional features and protections . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.1 Feedback disconnection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.2 Output overvoltage protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.3 Zero load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.4 Application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
6 Application ideas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
7 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
8 Order code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
9 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
L5973AD Pin settings
Doc ID 9552 Rev 9 3/22
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. When it is open, a signal synchronous with the
turn-off of the internal power is present at the pin. When connected to an
external signal at a frequency higher than the internal one, then the device is
synchronized by the external signal.
Connecting together the SYNC pin of two devices, the one with the higher
frequency works as master and the other one, works as slave.
3INH
A logical signal (active high) disables the device. With IHN higher than 2.2 V
the device is OFF and with INH lower than 0.8V, the device is ON.
If INH is not used the pin must be grounded. When it is open, an internal pull-
up disables the device.
4 COMP E/A output to be used for frequency compensation.
5FB
Stepdown feedback input. Connecting the output voltage directly to this pin
results in an output voltage of 1.235 V. An external resistor divider is required
for higher output voltages (the typical value for the resistor connected
between this pin and ground is 4.7 K).
6 VREF Reference voltage of 3.3 V. No filter capacitor is needed to stability.
7 GND Ground.
8 VCC Unregulated DC input voltage.
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P22

L5973ADTR

Mfr. #:
Buy L5973ADTR
Manufacturer:
STMicroelectronics
Description:
Switching Voltage Regulators 1.235 to 35V Step-Dn
Lifecycle:
New from this manufacturer.
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