LM34919BTLX National Semiconductor Corporation, LM34919BTLX Datasheet - Page 3

• Manufacturer Part Number: LM34919BTLX
• Description: Lm34919b Ultra Small 40v, 600 Ma Constant On-time Buck Switching Regulator
• Manufacturer: National Semiconductor Corporation

Pin Number
Pin Descriptions
C1
C3
D1
D2
D3
A1
A2
A3
B1
B3
RON/SD
SGND
Name
ISEN
RTN
VCC
BST
VIN
SW
SS
FB
On-time control and shutdown
Circuit Ground
Feedback input from the regulated
output
Sense Ground
Softstart
Current sense
Output from the startup regulator
Input supply voltage
Switching Node
Boost pin for bootstrap capacitor
Description
3
An external resistor from VIN to this pin sets the buck switch
on-time. Grounding this pin shuts down the regulator.
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.
Re-circulating current flows into this pin to the current sense
resistor.
An internal current source charges an external capacitor to
2.5V, providing the softstart function.
The re-circulating current flows through the internal sense
resistor, and out of this pin to the free-wheeling diode.
Current limit is nominally set at 0.64A.
Nominally regulated at 7.0V. An external voltage (7V-14V)
can be applied to this pin to reduce internal dissipation. An
internal diode connects VCC to VIN.
Nominal input range is 6.0V to 40V.
Internally connected to the buck switch source. Connect to
the inductor, free-wheeling diode, and bootstrap capacitor.
Connect a 0.022 µF capacitor from SW to this pin. The
capacitor is charged from V
each off-time.
Application Information
CC
via an internal diode during
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