LM34917A Datasheet, PDF (2/16 Pages) National Semiconductor (TI) – Ultra Small 33V, 1.25A Constant On-Time Buck Switching Regulator with Intelligent Current Limit

Connection Diagrams
Bump Side
20216629
Top View
20216630
Ordering Information
Order Number Package Type
LM34917ATL 12-Bump micro
LM34917ATLX
SMD
NSC Package
Drawing
TLA12UNA
Junction Temperature Range
−40°C to + 125°C
Supplied As
250 Units Tape and Reel
3k Units Tape and Reel
Pin Descriptions
Pin Number
A1
Name
SGND
Description
Sense Ground
A2
RTN
Circuit Ground
A3
FB
Feedback input from the regulated
output
B1
ISEN
Current sense
B2
RON/SD On-time control and shutdown
B3
SS
Softstart
C1,C2
VIN
Input supply voltage
C3
VCC
Output from the startup regulator
D1,D2
D3
SW
Switching Node
BST
Boost pin for bootstrap capacitor
Application Information
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.
The re-circulating current flows out of this pin to the free-
wheeling diode.
An external resistor from VIN to this pin sets the buck switch
on-time. Grounding this pin shuts down the regulator.
An internal current source charges an external capacitor to
2.5V, providing the softstart function.
Operating input range is 8.0V to 33V, with over-voltage
shutdown internally set at ≊35V. Transient capability is 50V.
Nominally regulated at 7.0V. Connect a 0.1 µF capacitor
from this pin to RTN. An external voltage (8V to 14V) can be
applied to this pin to reduce internal dissipation. An internal
diode connects VCC to VIN.
Internally connected to the buck switch source. Connect to
the inductor, diode, and bootstrap capacitor.
Connect a 0.022 µF capacitor from SW to this pin. The
capacitor is charged each off-time via an internal diode.
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