Datasheet

1
2
3
4
5
6
7
8
9
10
V
IN
PRE
COMP
V
CC
SW
PGND
IS
RT
SS
11
12
13
14
15
16
RAMP
SYNC
OUT
SD
BST
AGND
FB
17
18
19
20
PGND
IS
V
IN
SW
LM25005
SNVS411C –JANUARY 2006–REVISED MARCH 2013 www.ti.com
Connection Diagram
Figure 1. Top View
20-Lead HTSSOP
PIN DESCRIPTIONS
Pin(S) Name Description Application Information
Vcc tracks Vin up to 9V. Beyond 9V, Vcc is regulated to 7 Volts.
A 0.1uF to 1uF ceramic decoupling capacitor is required. An
1 VCC Output of the bias regulator
external voltage (7.5V – 14V) can be applied to this pin to
reduce internal power dissipation.
If the SD pin voltage is below 0.7V the regulator will be in a low
power state. If the SD pin voltage is between 0.7V and 1.225V
the regulator will be in standby mode. If the SD pin voltage is
2 SD Shutdown or UVLO input above 1.225V the regulator will be operational. An external
voltage divider can be used to set a line undervoltage shutdown
threshold. If the SD pin is left open circuit, a 5µA pull-up current
source configures the regulator fully operational.
3, 4 Vin Input supply voltage Nominal operating range: 7V to 42V
The internal oscillator can be synchronized to an external clock
5 SYNC Oscillator synchronization input or output with an external pull-down device. Multiple LM25005 devices
can be synchronized together by connection of their SYNC pins.
The loop compensation network should be connected between
6 COMP Output of the internal error amplifier
this pin and the FB pin.
This pin is connected to the inverting input of the internal error
7 FB Feedback signal from the regulated output
amplifier. The regulation threshold is 1.225V.
The internal oscillator is set with a single resistor, connected
8 RT Internal oscillator frequency set input between this pin and the AGND pin. The recommended
frequency range is 50KHz to 500KHz.
An external capacitor connected between this pin and the AGND
9 RAMP Ramp control signal pin sets the ramp slope used for current mode control.
Recommended capacitor range 50pF to 2000pF.
10 AGND Analog ground Internal reference for the regulator control functions
An external capacitor and an internal 10µA current source set
the time constant for the rise of the error amp reference. The SS
11 SS Soft-start
pin is held low during standby, Vcc UVLO and thermal
shutdown.
12 OUT Output voltage connection Connect directly to the regulated output voltage.
13, 14 PGND Power ground Low side reference for the PRE switch and the IS sense resistor.
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