LM34930 Datasheet, PDF (1/24 Pages) National Semiconductor (TI) – Ultra Small 33V, 1A Constant On-Time Buck Switching Regulator with Intelligent Current Limit

LM34930
www.ti.com
SNVS571B – MAY 2008 – REVISED APRIL 2013
Ultra Small 33V, 1A Constant On-Time Buck Switching Regulator with Intelligent Current
Limit
Check for Samples: LM34930
FEATURES
1
•2 Operating Input Voltage Range: 8V to 33V
• Input Over-Voltage Shutdown at 36V
• Input Absolute Maximum Rating of 44V
• Integrated 1A N-Channel Buck Switch
• Adjustable Output Voltage From 2.5V
• Switching Frequency Adjustable to 2 MHz
• Switching Frequency Remains Nearly
Constant With Load Current and Input Voltage
• Ultra-Fast Transient Response
• No Loop Compensation Required
• Adjustable Soft-Start Timing
• Thermal Shutdown
• Precision 2% Feedback Reference
• Input Over-Voltage Indicator at 19V
• Current Limit Scheme Helps Prevent Inductor
From Saturation in Load Fault Conditions
PACKAGE
• DSBGA-12, 1.77 mm x 2.1 mm
DESCRIPTION
The LM34930 constant On-Time Step Down
Switching Regulator features all the functions needed
to implement a low cost, efficient, buck bias regulator
capable of supplying in excess of 1A load current.
This high voltage regulator contains an N-Channel
Buck Switch, and is available in a DSBGA bumped
package. The constant on-time regulation principle
requires no loop compensation, results in fast load
transient response, and simplifies circuit
implementation. The operating frequency remains
constant with line and load. The valley current limit
results in a smooth transition from constant voltage to
constant current mode when current limit is detected
without the use of current limit foldback. To reduce
the possibility of saturating the inductor the valley
current limit threshold reduces as the input voltage
increases, and the on-time is reduced when current
limit is detected. Additional features include: Over-
voltage indicator, Input over-voltage shutdown, Vcc
under-voltage lock-out, thermal shutdown, and
maximum duty cycle limiting.
Typical Application, Basic Step-Down Regulator
8V - 33V
Input
C1
R_T
R4
OV
C5
VIN
BST
LM34930
SW
C4
L1
RT
nOV
D1
ISEN
SS
C6
R1
FB
VCC
GND
R2
C3
V_OUT
C2
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2
PRODUCTION DATA information is current as of publication date.
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Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
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