Friday, September 4, 2020

Circuit Schematic for Switching Regulator Step Up 12V to 24V 1A using LM2585

Eltronicschool. - One of the voltage regulator manufactored by Texas Instrument is LM2585 Adjustable that can be used to build switching regulator step up 12V to 24V 1A like this circuit schematic. LM2585-ADJ was chosen for its simplicity of use, because only requiring minimal external components like resistors and inductor. And additional that NPN switching/power transistor is integrated inside the regulator that able to withstand 3A maximum current and 65V maximum voltage. Switching frequency is defined by internal oscillator and it’s fixed at 100KHz.

And the circuit schematic for switching regulator step up 12V to 24V with 1A using LM2585 can be drawed like in Figure 1. below.

Circuit Schematic

Figure 1. Circuit Schematic for Switching Regulator Step Up 12V to 24V 1A using LM2585 (Source:

Component Part

C1 C2 33uF 25V 1Ω 6.3 x 5.4mm UWX1E330MCL1GB 647-UWX1E330MCL1
C3 0.1uF 50V 0Ω 1206 C1206C104J5RACTU 80-C1206C104J5R
C4 1uF 25V 1206 C1206C105K3RACTU 80-C1206C105K3R
C5 C6 220uF 35V 0.15Ω 10 x 10.2mm EEE-FC1V221P 667-EEE-FC1V221P
D1 0.45 V 3A 40V Schottky SMB B340LB-13-F 621-B340LB-F
IC1 LM2585S-ADJ TO-263 LM2585S-ADJ/NOPB 926-LM2585S-ADJ/NOPB
L1 120 uH 0.04Ω 30.5 x 25.4 x 22.1 mm PM2120-121K-RC 542-PM2120-121K-RC
R1 28 KΩ 1206 ERJ-8ENF2802V 667-ERJ-8ENF2802V
R2 R3 1.5 KΩ 1206 ERJ-8ENF1501V 667-ERJ-8ENF1501V
R4 1 KΩ 1206 RT1206FRE07931KL 603-RT1206FRE07931KL
LED1 RED LED 20mA 2.1V 0805 599-0120-007F 645-599-0120-007F


According Electronic-lab site describe the power switch is a 3-A NPN device that can standoff 65 V. Protecting the power switch are current and thermal limiting circuits and an under-voltage lockout circuit. This IC contains a 100-kHz fixed-frequency internal oscillator that permits the use of small magnetics. Other features include soft start mode to reduce in-rush current during start-up, current mode control for improved rejection of input voltage, and output load transients and cycle-by-cycle current limiting. An output voltage tolerance of ±4%, within specified input voltages and output load conditions, is specified for the power supply system.

Schematic is a simple boost topology arrangement based on datasheet. Input capacitors and diode should be placed close enough to the regulator to minimize the inductance effects of PCB traces. IC1, L1, D1, C1,C2 and C5,C6 are the main parts used in voltage conversion. Capacitor C3 is a high-frequency bypass capacitor and should be placed as close to IC1 as possible.All components are selected for their low loss characteristics. So capacitors selected have low ESR and inductor selected has low DC resistance.At maximum output power, there is significant heat produced by IC1 and for that reason, we mounted it directly on the ground plane to achieve maximum heat dissipation.

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