Spark Logic

AMS1117 low-dropout regulator connection guide

AMS1117 low-dropout regulator TO-252 fixed wiring guide with power, signal assignments, and bench checks.

SOT-223 fixed 4 contacts

TO-252 fixed

4 contacts Current package
SOT-223 adjustable 4 contacts
TO-252 adjustable 4 contacts

Advanced Monolithic Systems · Three lead positions and a connected metal tab.

2.5 V fixed output.

Power the fixed regulator

Required

Check the tab connection before attaching the board or heatsink. Measure the output against the device ground with a high-impedance meter.

CIN 10 µF between Input rail and GroundInput railCIN 10 µFGround
COUT 22 µF tantalum between Regulated rail and GroundRegulated railCOUT 22 µF tantalumGround

Bench checks

  • Confirm the input is present at VIN and the output is near the selected fixed voltage.

Advanced Monolithic Systems AMS1117, 800 mA datasheet, Application Hints. Supply and input bypass are fixture choices.

Connection scenarios

Check regulation under a small load

Switch the supply off, add a 1 kΩ resistive load from VOUT to GND, then reapply power.

  • Input rail
    • VIN (3)
    • Current-limited 7 V supply
    • CIN.1
  • Ground
    • GND (1)
    • Supply return
    • CIN.2
    • COUT.2
    • Meter common
    • RL.2
  • Regulated rail
CIN 10 µF between Input rail and GroundInput railCIN 10 µFGround
COUT 22 µF tantalum between Regulated rail and GroundRegulated railCOUT 22 µF tantalumGround
RL 1 kΩ between Regulated rail and GroundRegulated railRL 1 kΩGround

Bench checks

  • Compare loaded and unloaded output readings. The nominal current in milliamperes is the output voltage divided by 1 kΩ.
  • Check VIN at the part and probe VOUT for oscillation if the output moves unexpectedly.

Advanced Monolithic Systems AMS1117, 800 mA datasheet, Application Hints. Supply and input bypass are fixture choices. The 1 kΩ load is a fixture choice.

TO-252 fixed wiring map

Highlighted contacts are used in the required step or selected circuit. Select a contact to inspect it.

TO-252 fixed
View from the marked face, with the tab above the body and leads 1–3 below from left to right. Scroll the map to reach all contacts.
Selected pin details

TAB · VOUT

Output · Outputs

Metal tab connected to VOUT internally. Include its net when laying out the footprint.

Advanced Monolithic Systems AMS1117, 800 mA datasheet, p. 1

Electrical limits · Pin in the reference

Models and documents

The reference follows the Advanced Monolithic Systems 800 mA datasheet. Pin 1 is ground on the fixed version and the feedback input on the adjustable version.

AMS1117CD-1.5
1.5 V fixed output.
AMS1117CD-1.8
1.8 V fixed output.
AMS1117CD-2.5
2.5 V fixed output.
AMS1117CD-2.85
2.85 V fixed output.
AMS1117CD-3.3
3.3 V fixed output.
AMS1117CD-5.0
5.0 V fixed output.