Overview

The PT4115 (PT4115E / PT4115B) is an ubiquitous 30V 1.2A step-down (buck) constant-current LED driver IC manufactured by Power Trend Microelectronics (PowTech). Enclosed in a SOT-89-5 or ESOP-8 package, it is one of the most widely deployed LED driver ICs in modern maker electronics, driving MR16 lamps, automotive auxiliary lights, and DIY high-power LED spotlight modules (1W,3W,5W,10W1\text{W}, 3\text{W}, 5\text{W}, 10\text{W}).

Operating over an input voltage range of 6.0V to 30.0V DC, the PT4115 incorporates an internal 30V 1.2A power N-MOSFET, high-side current sensing (100 mV100\text{ mV} reference), thermal shutdown, and hysteretic PFM control to deliver up to 97% efficiency.

Quick reference

Input Supply Voltage (VIN)6.0 V to 30.0 V DC
Output LED CurrentUp to 1.2 A1.2\text{ A} continuous (Set by high-side sense resistor RSR_S)
Sense Voltage (VCSN)100 mV100\text{ mV} low-loss high-side threshold
Internal Switch Rating30 V,1.2 A30\text{ V}, 1.2\text{ A} integrated N-MOSFET
EfficiencyUp to 97%97\% typical
Dimming ModesPWM Dimming (100 Hz…50 kHz100\text{ Hz} \dots 50\text{ kHz}) & DC Analog Voltage Dimming (0.5V…2.5V0.5\text{V} \dots 2.5\text{V})
PackageSOT-89-5 / ESOP-8

Pinout (SOT-89-5 Package)

text
             ┌───┴───┐
        SW  1│ 1   5 │ CSN (Sense Input)
       GND  2│       │
       DIM  3│ PT4115│ 4 VIN (+6V to +30V)
             └───────┘
PinNameTypeDescription
1SWOutputInternal MOSFET Switch Drain (Connect to Freewheeling Schottky Diode & Inductor)
2GNDPowerGround Reference (0 V)
3DIMInputMulti-function Control Pin (Open = 100% LED Current; Low = Shutdown; PWM or DC Analog Input)
4VINPowerPower Supply Input (+6.0V to +30.0V DC)
5CSNInputHigh-Side Current Sense Input (Connect sense resistor RSR_S between VIN and CSN)

High-Side Buck LED Application Circuit

text
  +6V to +30V DC Supply ───┬─── [Pin 4: VIN]
                           │
                   [Sense Resistor R_S]
                           │
                           ├─── [Pin 5: CSN] ───► ( + ) High-Power LED String
                           │                             │
                      [PT4115]                           └─── [Inductor L1 (68µH)] ───┬─── [Pin 1: SW]
                           │                                                           │
                           └─── [Pin 2: GND] ─── Cathode Schottky Diode (SS14) ────────┘

Output LED Current Formula

ILED=100 mVRS=0.10VRSI_{LED} = \frac{100\text{ mV}}{R_S} = \frac{0.10\text{V}}{R_S}

For ILED=350 mA (1W LED)  ⟹  RS=0.10V0.35A≈0.28 Ω.\text{For } I_{LED} = 350\text{ mA } (1\text{W LED}) \implies R_S = \frac{0.10\text{V}}{0.35\text{A}} \approx 0.28\ \Omega. For ILED=700 mA (3W LED)  ⟹  RS=0.10V0.70A≈0.14 Ω.\text{For } I_{LED} = 700\text{ mA } (3\text{W LED}) \implies R_S = \frac{0.10\text{V}}{0.70\text{A}} \approx 0.14\ \Omega.

Common mistakes

  • Leaving DIM (Pin 3) pulled LOW: Pulling DIM below 0.3V0.3\text{V} places the PT4115 into ultra-low-power standby mode. For full constant brightness, leave DIM floating or pull HIGH to 3.3V/5V.
  • Forgetting PCB copper heatsinking under SOT-89 package: Running 1.2A1.2\text{A} continuously generates thermal heat. Solder the SOT-89 tab to a wide PCB ground copper plane.

Notes

  • PT4115 vs AL8807 vs CN7511: All three are 30V step-down LED drivers; PT4115 is packaged in SOT-89-5 and remains the budget standard on open-source hardware modules.

Assets & downloads