50V/1.5A High‑Brightness LED Constant‑Current Driver PT4115EE89E｜CRMICRO Authorized Distributor｜GS‑Micro

Keywords: PT4115EE89E | 50V 1.5A LED Constant‑Current Driver | PWM & Analog Dimming Driver IC | CRMICRO

Product Overview: PT4115EE89E is a CRMICRO buck LED constant‑current driver operating in continuous conduction mode. It supports 6‑50V input, max 1.5A output, ±3% output current accuracy, analog / PWM dimming, and comes in SOT89‑5 package. Suitable for automotive lighting, MR16 spotlights, industrial lighting, backlight and emergency lights. As an authorized distributor, GS‑Micro maintains spot inventory and provides samples, datasheets and hardware application reference designs.

⚡ Key Features

• Minimum external components to simplify PCB design

• Ultra‑wide input voltage range: 6V ~ 50V

• Maximum output current: 1.5A

• Multi‑function DIM pin: LED on/off, analog dimming, PWM dimming

• ±3% output current accuracy for excellent brightness consistency

• Up to 97% conversion efficiency for low power consumption & energy saving

• Constant‑current output configurable by external resistor

• Built‑in RCS open‑circuit protection, LED open‑circuit protection, thermal shutdown protection, under‑voltage lockout protection

• SOT89‑5 package with thermal pad connected to GND for reduced thermal resistance

Typical Application Scenarios

• MR16 spotlights, LED spotlights for halogen lamp replacement

• Automotive LED lamps (headlight, taillight, reading light, ambient light)

• LED backup lights, fire emergency lighting

• LED signal lights, illuminated signs, advertising light boxes

• SELV Safety Extra‑Low‑Voltage lighting systems

• LCD TV & industrial display LED backlight driving

Key Electrical Parameters

Typical Application Schematic

Pin Definition

Operating Principle

PT4115EE89E, together with inductor (L) and current‑sense resistor (RS), forms a self‑oscillating buck LED constant‑current driver working in continuous conduction mode. At VIN power‑up, initial currents of inductor L and sense resistor RS are zero, so does LED output current. The CS comparator outputs high and internal power switch turns on. Current flows from VIN through inductor L, sense resistor RS, LEDs and internal power switch to GND.

Current rising slope is determined by VIN, inductor L and LED forward voltage drop, generating voltage drop V_CSN across RS. When (V_IN‑V_CSN)＞230mV, CS comparator output goes low and internal power switch turns off. Inductor freewheeling current flows through L, RS, LEDs and Schottky diode D. When (V_IN‑V_CSN)＜170mV, power switch turns on again. This cycle stabilizes the average LED output current.

High‑side current‑sensing architecture reduces external component count. With 1% precision sense resistor, LED output‑current accuracy reaches ±3%. Derate thin‑film SMD resistors to 70% of rated power. For 1A output current, two parallel 1206 resistors (0.33Ω and 0.47Ω) are recommended.

The DIM pin supports PWM dimming: output shuts down below 0.3V and runs at full current above 2.5V and ≤5V. Supported PWM dimming frequency:100Hz~20kHz. 0.5V‑2.5V DC voltage enables analog dimming. DIM pin can be left floating. When DIM is pulled below 0.3V, IC enters standby mode with max 100uA quiescent current.

Built‑in TSD thermal shutdown protection triggers at 155℃ and auto‑recovers at 130℃. RCS open‑circuit protection and LED open‑circuit protection enhance system robustness.

Application Notes

Setting Average LED Output Current via External Sense Resistor RS

LED average output current is set by sense resistor RS placed between VIN and CSN: I_OUT＝0.2/Rs. Condition: DIM pin is floating or DIM voltage＞2.5V and ≤5V. RS defines maximum output current; actual output current can be reduced via DIM pin.

Analog Dimming (DC Voltage Dimming)

Apply DC V_DIM on DIM pin to lower LED output current; maximum current is defined by RS. LED average‑current formula: I_OUT=(0.2×VDIM)/(2.5×RCS).

Full‑scale output I_OUT=0.2/Rs is maintained when V_DIM ranges 2.5V~5V.

PWM Signal Dimming

Maximum output current is set by RS. Apply variable‑duty‑cycle PWM signal to DIM pin for brightness adjustment. Advantage of PWM dimming: LED chromaticity will not shift. Recommended PWM frequency ≥100Hz to avoid visible flicker, maximum up to 20kHz. When PWM high‑level is 2.5V~5V: I_OUT=(0.2×D)/RCS (D=duty cycle).

Shutdown Mode

DIM pin voltage below 0.3V triggers shutdown mode, maximum quiescent current 100μA.

Soft‑Start Mode

Adding capacitor from DIM pin to GND realizes soft‑start by slowly ramping DIM voltage. 0.47µF 0805 ceramic capacitor is recommended. A Schottky diode across capacitor to VIN can accelerate discharge and solve abnormal startup after frequent power cycling.

Freewheeling Diode Selection

Select fast‑recovery Schottky diode with low forward voltage, low parasitic capacitance and low leakage current. Reserve ≥30% margin for current & voltage rating. Pay close attention to reverse leakage at high temperature to avoid extra power dissipation. Low‑Vf Schottky diode is mandatory for AC24V rectification applications.

Input Capacitor Selection

Place low‑ESR bypass capacitor close to VIN pin, which must withstand sufficient RMS ripple current. 50V rated voltage, capacitance ≥22μF, X7R‑grade or higher ceramic capacitor is recommended. Add an extra 0.1µF ceramic capacitor near VIN pin for noise suppression.

Inductor Selection

Recommended switching frequency:100kHz~500kHz, typical value 200KHz; ripple current set to 30% of peak switch current. Inductor saturation current I_SAT≥1.3×I_LP for 30% design margin. DCR less than 50mΩ is preferred for high efficiency.

Output Capacitor Selection & Output Ripple Reduction

Output capacitor is optional for most applications. To suppress output current ripple, a 2.2μF capacitor in parallel across LED terminals works well; larger value further reduces ripple. Output capacitor does not change operating frequency or efficiency, but affects startup delay and dimming response speed.

PCB Layout & Thermal Guidelines

• Place sense resistor RCS close to VIN and CSN pins to minimize sensing error;

• Keep power loops (input capacitor, sense resistor, inductor, Schottky diode) as short as possible;

• Keep switching‑node traces short and away from IC to reduce radiated interference;

• Single‑point grounding for power‑ground and signal‑ground; place 0.1µF ceramic capacitor near VIN;

• Connect thermal pad to GND; use large copper pours on PCB, 1oz copper over 25mm² area for better heat dissipation;

Test Considerations

• Electronic‑load CV‑mode test may behave abnormally without output capacitor; increase output capacitance to extend startup time;

• Use real LED loads for power‑on / power‑off and dynamic‑performance tests;

Q1: How to set the maximum output current of PT4115EE89E?
A: Constant output current is defined by sense resistor RS between VIN‑CSN. Calculation formula Iout=0.2/Rs. 1% precision sense resistor delivers ±3% constant‑current accuracy.

Q2: What dimming modes are supported by DIM pin?
A: DIM pin supports PWM digital dimming and 0.5V‑2.5V analog voltage dimming. IC enters low‑power standby when DIM＜0.3V. PWM dimming keeps LED color temperature unchanged, maximum dimming frequency reaches 20kHz.

Q3: What advantages does PT4115EE89E have compared with standard PT4115?
A: Input voltage raised up to 50V, max output 1.5A while conventional PT4115 is mostly 30V/1.2A. Improved ±3% current accuracy and enhanced multi‑level protections, suitable for high‑voltage high‑power LED lighting.

Q4: How to handle thermal shutdown issue on PT4115EE89E?
A: Check input‑to‑output voltage differential; optimize PCB copper pour for thermal dissipation and ensure thermal pad connected to GND; verify saturation current rating of inductor and leakage performance of Schottky diode. Thermal shutdown triggers at 155℃ and auto‑recovers at 130℃.

Q5: Will LED open‑circuit condition damage the chip?
A: The IC integrates LED open‑circuit protection and RCS open‑circuit protection. It enters safe mode under open‑load condition and automatically resumes normal operation after load recovery.