AAT1401IUQ-T1 – Complete Datasheet Summary
(Information extracted from Skyworks AAT1401.pdf, Rev. 202113A • 27 June 2012)

1. Device Overview1.1 Product NameAAT1401 – 1 MHz Boost Single-Channel White-LED Driver with 32-Step S²C-Wire & Filtered-PWM Dimming
2. 1.2 Full Ordering Code Highlighted
   AAT1401IUQ-T1
   • Package: WLCSP-10 (0.3 mm pitch, 1.15 mm × 1.55 mm)
   • Shipping: 3 000 pieces / 7-inch tape-and-reel
   • Green / Halogen-free / RoHS compliant
3. 1.3 One-Line Description
   A 2.7-5.5 V input, current-mode boost converter that drives up to 6 white LEDs (28 V max) at 31 mA with dual-mode dimming, 85 % efficiency and <1 µA shutdown.
4. Feature Summary• 2.7 V – 5.5 V input range (single-cell Li-ion)• 28 V maximum output voltage (6 × 4 V VF LEDs)• Integrated 1 A / 650 mΩ power NMOS – no external FET needed• 1 MHz switching frequency enables 4.7 µH – 22 µH chip inductors & 0603 caps• Precision current-sink regulation (10 – 31 mA set by external RSET)• Dual dimming paths– 32-step single-wire S²C-wire (100 % → 2 %)– Filtered PWM 100 Hz – 100 kHz (100 % → 1 %) – ideal for CABC• True dc LED current (no ripple) in PWM mode – flicker-free / audible-noise-free• Soft-start (4 ms typ), over-voltage (1.2 V thresh), over-temperature (155 °C) protections with automatic recovery• <1 µA shutdown current; 430 µA quiescent; 2.3 mA switching current• Tiny WLCSP-10 (1.15 mm × 1.55 mm, 0.3 mm bump pitch)
5. Typical Applications• Mobile handsets / smart-phones• Digital still cameras / camcorders• Netbooks / tablets / notebook displays• Portable media / navigation players• White-LED backlighting up to 6 series LEDs
6. Pin-out & Functions (WLCSP-10 1.15 × 1.55 mm)A1 LX – switch node, connect to 10 µH inductor & Schottky anodeA2 IN – 2.7-5.5 V supply input; place 4.7 µF/6.3 V X5R close to pinA3 EN/SET – enable + S²C-wire serial dimming input (20 kHz – 1 MHz)B1 PGND – power ground; star to system GNDB2 – – (no ball)B3 PWM – filtered-PWM dimming input (100 Hz – 100 kHz); tie to VIN if unusedC1 GND – analog groundC2 – – (no ball)C3 COMP – compensation; connect 56 nF to GND (sets soft-start & filter pole)D1 CS – current-sink input; connect to cathode of last LEDD2 RSET – connect RSET to GND to set ILED (1.2 V reference, 258 ratio)D3 OVP – over-voltage feedback; resistor divider from VOUT to OVP to GND
7. Absolute Maximum RatingsIN, EN/SET, PWM to GND ........................ –0.3 V to 6.0 VLX to GND ....................................... –0.3 V to 34 VCS, OVP to GND ................................. –0.3 V to 28 VJunction temperature ........................... –40 °C to +155 °CStorage temperature ............................ –55 °C to +125 °CSoldering (lead, 10 s) .......................... 300 °C
8. Recommended Operating ConditionsParameter ........................................ Min Typ MaxVIN ............................................. 2.7 – 5.5 VVOUT (boost) .................................... VIN+3 – 28 VLED current per string ......................... 10 – 31 mAInductor ........................................ 4.7 10 22 µHPWM frequency ................................ 0.1 – 100 kHzAmbient temperature ........................... –40 – +85 °C
9. Electrical Characteristics (VIN = 3.6 V, L = 10 µH, RSET = 10 kΩ, TA = –40 °C to +85 °C unless noted)Input voltage range ............................. 2.7 V – 5.5 VShutdown current (VEN=0) ...................... <1 µAQuiescent current (no switching) ............... 430 µA typ, 700 µA maxSwitching supply current ........................ 2.3 mA typNMOS RDS(on) .................................... 650 mΩ typSwitching frequency ............................. 1.0 MHz ±20 %Maximum duty cycle ............................. 94 %Soft-start time (CCOMP = 56 nF) ................. 4 msCurrent-sink voltage @ 31 mA ................... 500 mV typCurrent-sink accuracy (RSET = 10 kΩ) ........... 31 mA ±10 %Over-voltage threshold (OVP) ................... 1.20 V ±0.1 V (75 mV hysteresis)Over-temperature shutdown ...................... 155 °C (15 °C hysteresis)Efficiency (6 LEDs, 20 mA, VIN = 3.6 V) ......... 85 % typ
10. Setting LED Current & Dimming8.1 Maximum current:ILED_max = (VSET / RSET) × 258 VSET = 1.20 VExample: RSET = 15 kΩ → ILED_max = 20 mA
11. 8.2 S²C-wire dimming (EN/SET pin)

• First rising edge enables device & latches full current (code 1) after 500 µs tLAT
• Each additional rising edge increments code (2 → 32) wrapping to 1 again
• Code 32 = 2 % of ILED_max; hold pin high to keep level
• Pull low >500 µs to enter shutdown (<1 µA)
• 8.3 Filtered-PWM dimming (PWM pin)
• DC = 100 % → full ILED_max; DC = 1 % → 1 % ILED_max
• Frequency 100 Hz – 100 kHz; pin high disables PWM (100 %)

1. External Component Selection (typical)Inductor ........................... 10 µH, ≥900 mA ISAT, ≤164 mΩ DCR (e.g. Sumida CDRH3D18-100)Input capacitor .................... 4.7 µF / 6.3 V / X5R / 0603 (Murata GRM188R60J475K)Output capacitor ................... 0.1 µF / 50 V / X7R / 0603 (Murata GRM188R71H104K)COMP capacitor ..................... 56 nF / 16 V / X7R / 0603 (sets 4 ms soft-start & filter pole)Rectifier diode .................... 30-40 V Schottky, ≥350 mA, VF ≤0.37 V @ 100 mA (Diodes SDM20U40)OVP divider ........................ R1 = 1 MΩ, R2 = 51 kΩ → OVP ≈ 24 V (adjust for LED string)
2. PCB Layout Guidelines• Place input capacitor (CIN) within 2 mm of IN and PGND balls.• Keep LX trace short & wide (<10 mm); minimize loop area to reduce EMI.• Star-connect GND & PGND to exposed copper under WLCSP for heat-spreading.• Route high-impedance OVP and RSET traces away from LX; add guard ring if possible.• Place Schottky diode cathode and COUT as close as possible to LED string to limit ripple.
3. Evaluation KitAAT1401 evaluation board (AAT1401IUQ-DB1) includes:

• Six white LEDs, PIC12F675 MCU for S²C-wire demo, push-buttons for UP/DOWN/CYCLE, USB/DC jack, test points and BOM listed in datasheet.

1. Package Information (WLCSP-10)Body size: 1.15 mm × 1.55 mmBall matrix: 5 × 2, 0.3 mm pitchBall diameter: 0.2 mm ±0.025 mmHeight: 0.37 mm maxMarking: “F4” + two-digit date code (top-view through lens)
2. Ordering InformationPart Number ..................... Package ............ Marking ............... Reel SizeAAT1401IUQ-T1 ................. WLCSP-10 ........... F4YY ................. 3 000 / 7-in reel