Electronics, PCB Design and PCB Layout

Custom Firmware, Electronics Design, and PCB Layout

Electronics Design
Firmware Development
Software Development
Embedded Design
PCB Layout
Digital Signal Processing (DSP)
Reverse Engineering
Device Driver Development
Motor Controllers
Data Acquisition Systems
Palm OS Software
Windows CE Software
Pocket PC Software
Design for Manufacturing
Through Hole to Surface Mount (SMT) Conversion 
Microchip PIC Consultant
MSP430 Development
DSP56 Development
RoHs Redesign
Design for USB

Silver Board Contract Assembly

LM25085 Switching Regulator Design Calculator

The LM25085 is an affordable switching regulator in a small package, with a wide input voltage range. It's our experience that it's much better than the similar LM3489 which tends to run at too fast a frequency and overheat. The LM25085 has pad under it for better heat transfer. It also has very good design equations which are easy to follow, but tedious to implement by hand. This standard design uses the Vishay Si7465 P channel MOSFET, which has a low gate chare of only 40nC. The power disipation of the LM25085 is directly proportional to the gate charge of the MOSFET so this should be minimized.

R3 and C3 form a product. So you can scale them together. For example if you use a 0.01uF cap for C3 then divide the calculator's result for R3 by a factor 3.

Maximum Input Voltage (Vin(max)) (Volts)
Nominal Input Voltage (Vin(nominal)) (Volts)
Minimum Input Voltage (Vin(min)) (Volts)
Output Voltage (Vout) (Volts)
Diode Forward Voltage (Vd) (Volts)
Maximum Output Current (Imax). (Amps)
Minimum Output Current (Imin) (Amps)
Maximum Output Voltage Ripple (mVpp)
Current Sense Resistor.
Choose .01 ohms if unsure.
Top Feedback Resistor Rf1
Choose 10 Kohms if unsure.
Desired Switching Frequency (Fs) (KHz)
MOSFET On Time (nano secs)
MOSFET Off Time (nano secs)
MOSFET Gate Charge (nC)
Duty Cycle (%)
Ton(min) (Minimum Switch On Time) (nano secs)
Ton(max) (Maximum Switch On Time) (nano secs)
Maximum Diode Power (W)
Maximum LM25085 Power (W)
Maximum Current Sense Resistor Power (W)
Inductor (L) (uH)
Current Limit (Icl).
(Peak Inductor Current)
Output Capacitor, (Cout) (uF)
Input Capacitor, (Cin) (uF)
Rf2 (Kohms)
RT (Kohms)
Radj (ohms)
Cadj (pf)
R3*C1 Product
C1 (pf)
R3 (Kohms)
C2 (uf)

Daycounter specializes in contract electronics design. Contact us to get a quote.

[Employment] [Downloads] [Articles] [Contact Us]

Salt Lake City, UT, USA

Disclaimer: Daycounter, Inc. doesn't guarantee the accuracy of any of it's content. Use at your own risk.

© Copyright 2016 Daycounter, Inc. All rights Reserved.

Soil Moisture Sensor Probe

Water Level Sensor