Spark Logic

AMS1117 low-dropout regulator connection guide

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

SOT-223 fixed 4 contacts
TO-252 fixed 4 contacts
SOT-223 adjustable 4 contacts

TO-252 adjustable

4 contacts Current package

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

Set the adjustable output to about 3.3 V

Required

Use a 5 V supply, R1 = 120 Ω and R2 = 196 Ω. Observe the polarity and voltage rating of the output tantalum capacitor.

  • Input rail
    • VIN (3)
    • Current-limited 5 V supply
    • CIN.1
  • Ground
    • Supply return
    • CIN.2
    • COUT.2
    • R2.2
    • Meter common
  • Output
  • Feedback
CIN 10 µF between Input rail and GroundInput railCIN 10 µFGround
COUT 22 µF tantalum between Output and GroundOutputCOUT 22 µF tantalumGround
R1 120 Ω between Output and FeedbackOutputR1 120 ΩFeedback
R2 196 Ω between Feedback and GroundFeedbackR2 196 ΩGround

Bench checks

  • Expect about 1.25 V across R1 and about 3.3 V from VOUT to ground.
  • The nominal output includes the ADJ pin current: 1.25 V × (1 + 196/120) + 55 µA × 196 Ω ≈ 3.30 V.

Advanced Monolithic Systems AMS1117, 800 mA datasheet, Application Hints, Figure 2. The resistors and supply voltage are chosen for this fixture.

TO-252 adjustable wiring map

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

TO-252 adjustable
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

1 · ADJ

Input · Control

Feedback node. The regulator holds the output about 1.25 V above this node.

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
Adjustable TO-252. Set VOUT with the feedback divider.