Spark Logic

APW8805 / APW8805A / APW8805B buck converter connection guide

APW8805 / APW8805A / APW8805B buck converter (TDFN 3 × 3 mm (QB)) connection guide. Build the 1.05 V buck circuit. Check enable and power good.

TDFN 3 × 3 mm (QB)

11 contacts Current package

ANPEC Electronics · Ten perimeter leads and one exposed ground pad.

Build the 1.05 V buck circuit

Required

With power off, join VIN and VCC to the same 2.6–6 V rail. Join both SW pins, keep that copper compact, and leave NC open. Drive EN low during initial power-up. The optional feed-forward capacitor across R1 is omitted in this drawing.

Build the 1.05 V buck circuitVIN22µ100kENPOKVINVCCAPW8805SW1.5µHVOUT4.7kFB15k2×22µGND / EPGND
  • Input
    • CIN.1
    • RPG.1
    • Input supply positive
  • Ground
    • CIN.2
    • COUT1.2
    • COUT2.2
    • R2.2
    • Input return
  • Enable
    • →
    • Enable control
  • Switch node
    • →
    • →
    • L1.1
  • Output
    • L1.2
    • R1.1
    • COUT1.1
    • COUT2.1
    • Load positive
  • Feedback
    • →
    • R1.2
    • R2.1
  • Power good
    • →
    • RPG.2
    • Power-good monitor

Bench checks

  • Verify continuity from pins 4, 5 and the exposed pad to ground. Check VIN for shorts before applying a current-limited supply.
  • Drive EN high after the input has settled. The divider sets 0.8 × (1 + 4.7/15) ≈ 1.05 V nominal. Check at the output capacitor.
  • Choose L1 for the peak inductor current, and check capacitor effective capacitance under bias, ripple and PCB temperature before increasing load.

ANPEC APW8805 Rev. A.4, Typical Application Circuit, p. 10

Connection scenarios

TDFN 3 × 3 mm (QB) wiring map

External wiring example · Build the 1.05 V buck circuit

Highlighted contacts are used in the required step or selected circuit. Select a contact to highlight its wiring nets.

TDFN 3 × 3 mm (QB) · Top view, with pin 1 at upper left. The exposed ground pad is on the underside.
Dashed outline shows the underside pad schematically. See the package drawing for the footprint.
Selected pin details

6 · SW

Output · Outputs

Switch node, tied to pin 7 and the inductor input.

ANPEC APW8805 / A / B datasheets, p. 2 and Pin Description

Connected nets

Electrical limits · Pin in the reference

Dashed lines show external connections in this wiring example.

Models and documents

Choose the exact suffix for the enable thresholds and light-load behavior. The APW8805B overview lists 0.6 V as a minimum output, while its feedback specification and application equation use 0.8 V. The circuit here uses the documented 0.8 V reference.

APW8805
Automatic PFM/PWM. Order code: APW8805QBI-TRG.
APW8805A
Forced PWM. Order code: APW8805AQBI-TRG.
APW8805B
Automatic PFM/PWM; documented startup into a pre-biased output. Order code: APW8805BQBI-TRG.