Features • Functional Input Voltage Range: 8V to 33V • Micro SMD package • Input Over-Voltage Shutdown at ≊35V • Transient Capability to 50V • Integrated N-Channel buck switch • Valley current limit varies with VIN and VOUT to reduce excessive inductor current • On-time is reduced when in current limit • Integrated start-up regulator • No loop compensation required • Ultra-Fast transient response • Maximum switching frequency: 2 MHz • Operating frequency remains nearly constant with load current and input voltage variations • Programmable soft-start • Precision internal reference • Adjustable output voltage • Thermal shutdown Description The LM34917A Step-Down Switching Regulator features all the functions needed to implement a low cost, efficient, buck bias regulator capable of supplying at least 1.25A to the load. To reduce excessive switch current due to the possibility of a saturating inductor the valley current limit threshold changes with input and output voltages, and the on-time is reduced when current limit is detected. This buck regulator contains an N-Channel Buck Switch, and is available in the 12 pin micro SMD package. The constant on-time feedback regulation scheme requires no loop compensation, results in fast load transient response, and simplifies circuit implementation. The operating frequency remains constant with line and load variations due to the inverse relationship between the input voltage and the on-time. The valley current limit results in a smooth transition from constant voltage to constant current mode when current limit is detected, reducing the frequency and output voltage, without the use of foldback. Additional features include: VCC under-voltage lock-out, input over-voltage shutdown, thermal shutdown, gate drive under-voltage lock-out, and maximum duty cycle limit.

LM34917A   8.00 <= V in Lower  V   <= V in Upper  V   <= 33.00 V out 2.51 <=  V <= 30.00 I out    A <= 1.20 Ambient Temperature  °C <= 100 What are WEBENCH® tools? LM34917A Basic Step Down Regulator MY BRIEFCASE                                       Click any "Briefcase" icon to add an item

Typical Application *click for larger image LM34917A Basic Step Down Regulator	Block Diagram *click for larger image LM34917A Typical Application and Block Diagram
Typical Performance *click for larger image

Datasheet

Title		Size	Date	Other Language
	LM34917A Ultra Small 33V, 1.25A Constant On-Time Buck Switching Regulator with Intelligent Current Limit	555 Kbytes	8-May-08

Featured Application Notes

Title		Size	Date	Other Language
	AN-1601: Application Note 1601 LM34917A Evaluation Board	1142 Kbytes	10-Apr-08

More Application Notes

Title		Size	Date	Other Language
	AN-1349: Application Note 1349 LM34910 Evaluation Board	562 Kbytes	18-Nov-04
	AN-1650: Application Note 1650 LM34919 Evaluation Board	338 Kbytes	8-Jun-07	中文
	AN-1601: Application Note 1601 LM34917A Evaluation Board	1142 Kbytes	10-Apr-08

Design Tools

Title	Size	Date
LM34917A Quick Start Calculator	369 Kbytes	31-Jul-2009

Reliability Metrics

Part Number	Process	EFR Reject	EFR Sample Size	PPM	LTA Rejects	LTA Device Hours	FITS	MTTF (Hours)
LM34917ATL	ABCD150XV1	0	3868	0	0	2595000	2	736338335
LM34917ATLX	ABCD150XV1	0	3868	0	0	2595000	2	736338335

Note: The Early Failure Rates (EFR) were calculated as point estimate PPM based on rejects and sample size for EFR. The Long Term Failure Rates were calculated at 60% confidence using the Arrhenius equation at 0.7eV activation energy and derating the assumed stress temperature of 150°C to an application temperature of 55°C.

For more information on Reliability Metrics, please click here.