LM34910CSD National Semiconductor, LM34910CSD Datasheet - Page 3

• Manufacturer Part Number: LM34910CSD
• Description: High Voltage (50V, 1.25A) Step Down Switching Regulator
• Manufacturer: National Semiconductor

Pin Descriptions
Pin
10
1
2
3
4
5
6
7
8
9
R
Name
S
BST
RTN
ON
I
V
SW
FB
SS
V
SEN
GND
CC
IN
/SD
Switching Node
Boost pin for boot-strap capacitor
Current sense input
Sense Ground
Circuit Ground
Feedback
Softstart
On-time Control and Shutdown
Output from the start-up regulator
Input supply voltage
Description
3
Internally connected to the buck switch source. Connect
to the external inductor, diode, and boost capacitor.
Connect a 0.022 µF capacitor from SW to this pin. An
internal diode charges the capacitor during the off-time.
Internally the current sense resistor connects from this
pin to S
the free-wheeling diode. Current limit is set at 1.25A.
Re-circulating current flows into this pin to the current
sense resistor.
Ground for all internal circuitry other than the current limit
detection.
Internally connected to the regulation and over-voltage
comparators. The regulation level is 2.5V.
An internal 11.5 µA current source charges an external
capacitor to 2.5V to provide the softstart function.
An external resistor from V
switch on-time. Grounding this pin shuts down the
regulator.
Nominally regulated to 7.0V. An external voltage
(8V-14V) can be connected to this pin to reduce internal
dissipation. An internal diode connects V
Nominal input range is 8.0V to 50V.
GND
. Re-circulating current flows out of this pin to
Application Information
IN
to this pin sets the buck
CC
to V
www.national.com
IN
.