CRMICRO Primary Agent DC to DC Buck constant current drive IC PT4119E89E

6‑30V/0.8A Buck LED Constant‑Current Driver PT4119E89E｜CRMICRO Authorized Distributor｜GSMicro

Keywords: PT4119E89E | 6‑30V 0.8A LED constant‑current driver | PWM & analog dimming driver IC | CRMICRO

Product Overview: PT4119E89E is a CRMICRO buck LED constant‑current driver operating in continuous conduction mode. It accepts 6‑30V input, max 0.8A output, ±3% output‑current accuracy, supports analog / PWM dimming, available in SOT89‑5 and ESOP8 packages. Suitable for automotive lighting, LED spotlights, emergency lights and signal indicators. As an authorized distributor, GSMicro maintains spot inventory and provides samples, datasheets and hardware application reference designs.

⚡ Key Features

• Minimal external components to simplify PCB design

• Wide input‑voltage range: 6V ~ 30V

• Maximum output current: 0.8A

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

• ±3% output‑current accuracy for consistent brightness performance

• Up to 97% conversion efficiency for low power dissipation

• Constant‑current output configurable by external resistor

• Built‑in LED open‑circuit protection, TSD thermal‑shutdown protection

• Optional ESOP8 package with exposed thermal pad for improved heat dissipation

Typical Application Scenarios

• Low‑voltage LED spotlights as halogen‑lamp replacements

• Automotive LED lighting fixtures

• LED emergency backup lamps

• LED signal and indicator lights

Key Electrical Parameters

Typical Application Schematic

Pin Definition

Operating Principle

PT4119E89E, together with inductor L and current‑sense resistor RS, forms a self‑oscillating buck LED constant‑current controller working in continuous conduction mode (CCM). At VIN power‑up, initial currents of inductor L and sense resistor RS are zero and LED output current equals zero. The CS comparator outputs high level and the internal power switch turns on, pulling the SW node low. Current flows from VIN through inductor L, sense resistor RS, LED load and internal power switch to GND. The current slew rate is determined by VIN, inductor L and LED forward voltage drop. A differential voltage V_CSN is developed across RS. When (V_IN‑V_CSN)＞115mV, the CS comparator pulls its output low and the internal power switch turns off. Inductor free‑wheeling current flows through L, RS, LED and Schottky diode D. When (V_IN‑V_CSN)＜85mV, the power switch turns on again. This cycle stabilizes the average LED output current.

The high‑side current‑sensing topology reduces external component count. With a 1% precision sense resistor, LED output‑current accuracy can reach ±5%.

The DIM pin accepts PWM signals for dimming. LED current is disabled when DIM is below 0.3V and enabled at full scale above 2.5V. Valid PWM dimming frequency ranges from 100Hz to above 20kHz. Analog dimming is available by applying 0.5V‑2.5V DC voltage to DIM. The DIM pin may be left floating during normal operation. When DIM goes below 0.3V, the internal power switch is off and LED current drops to zero. The internal regulator remains active during shutdown with typical quiescent current of 95uA.

Built‑in TSD thermal‑shutdown protection is implemented and the package includes an exposed thermal pad. Thermal‑shutdown activates at 160℃ to protect IC and system. The exposed pad of ESOP8 enhances power‑handling capability. An external NTC thermistor may be connected from DIM to near the LEDs for temperature‑based LED‑current derating.

Application Notes

Setting Average LED Current via External Sense Resistor RS

Average LED current is set by resistor RS placed between VIN and CSN: I_OUT＝0.1/Rs (Rs≥0.082Ω). This formula holds when DIM is floating or driven above 2.5V and below 5V. RS defines the maximum LED output current; the actual output current can be reduced via the DIM pin.

Analog Dimming (DC‑Voltage Dimming)

Apply DC voltage V_DIM to DIM to reduce LED output current. Maximum LED current is defined by 0.1/RS.

Full‑scale output I_OUT=0.1/Rs is maintained for V_DIM from 2.5V to 5V.

PWM‑Signal Dimming

Maximum average LED current is set by sense resistor RS between VIN‑CSN. Apply variable‑duty‑cycle PWM signal to DIM to adjust output current for brightness control. PWM dimming preserves LED chromaticity. Recommended PWM frequency ≥100Hz to avoid visible flicker, maximum up to 20kHz.

Shutdown Mode

Drive DIM below 0.3V to enter shutdown mode. Typical quiescent current remains below 95μA.

Soft‑Start Mode

Connect a capacitor from DIM to GND to implement soft‑start. DIM voltage rises slowly at power‑up and LED current ramps gradually. Approximate relationship: 0.8ms/nF.

LED Open‑Circuit Protection

PT4119E89E incorporates intrinsic open‑load protection. When LED load is open, SW node floats and the IC enters safe low‑power state. Both LED and IC remain undamaged. Normal operation resumes once load is reconnected.

Input Bypass Capacitor Selection

Place a low‑ESR bypass capacitor close to the VIN pin. High ESR increases power loss. The bypass capacitor must withstand large peak currents and smooth input transients. Minimum 4.7μF for DC input; 100μF tantalum capacitor is recommended for AC‑rectified or low‑input‑voltage applications. Prefer X5R / X7R dielectric for stability across temperature and voltage. Mount capacitor as near to IC power pins as practical.

Inductor Selection

Recommended inductor value: 27uH ~ 100uH. Inductor saturation‑current rating should be 30%~50% higher than maximum output current. Larger inductance is preferred at lower output currents for improved constant‑current performance. Place inductor close to VIN and SW pins to minimize resistive losses.

Example CoilCraft part‑number suggestions are shown below:

Inductor must satisfy the maximum operating‑frequency specification of PT4119E89E.

SW On‑Time calculation:

SW Off‑Time calculation:

Parameters:
L: Inductance (H)
rL: Inductor DC resistance (Ω)
R_S: Sense resistor value (Ω)
Iavg: Average LED current (A)
ΔI: Inductor ripple current peak‑to‑peak (A) {typically set to 0.3 × Iavg}
V_IN: Input supply voltage (V)
V_LED: Total LED forward voltage (V)
R_SW: Internal switch on‑resistance (Ω) {typical 0.6Ω}
V_D: Diode forward drop (V)

Diode Selection

For optimum efficiency and performance, select a fast‑recovery Schottky diode featuring low forward voltage, low parasitic capacitance and low leakage current. Derate current and voltage ratings by at least 30% for reliability. Pay attention to reverse leakage at 85℃; excessive leakage increases system power dissipation. For AC‑12V rectification path, use a low‑Vf Schottky diode to reduce device power loss.

Reducing Output‑Current Ripple

To suppress output ripple, place a capacitor in parallel across LED load as shown in diagram. A 1μF capacitor reduces ripple by approximately one‑third. Larger capacitance further attenuates ripple. Output capacitor does not change operating frequency or efficiency, but affects startup delay and dimming response.

Low‑Input‑Voltage Operation Notes

When input approaches output voltage and falls below VUVLO, internal power switch stays off. System starts only after VIN exceeds (VUVLO＋500mV). Even above this threshold, if VIN is very close to LED voltage, the converter runs at high duty cycle. This raises power dissipation, especially for VIN＜10V, and may trigger thermal shutdown under sustained operation. Maintain reasonable input‑to‑output voltage headroom in your design. If supply drops below VUVLO during operation, the switch turns off and output is disabled.

Thermal Design Recommendations

Evaluate power limits for high‑ambient‑temperature or high‑load applications. Use 1oz copper pour over at least 25mm² PCB area for current‑carrying traces. Maximize copper contact area between IC thermal pad and GND plane. Poor inductor choice or excessive parasitic capacitance on switching node degrade efficiency. ESOP8 package is recommended for high‑power applications due to superior thermal performance compared to SOT89‑5.

Load‑Current Thermal Compensation

High‑brightness LEDs often require thermal compensation. PT4119 internal circuitry stabilizes output current. You may connect an NTC thermistor from DIM to the LED side. As LED temperature rises, DIM voltage decreases and LED current is reduced to protect the LEDs.

IC Thermal‑Shutdown (TSD)

PT4119 implements TSD protection. When junction temperature exceeds 160℃, output is disabled. Operation auto‑resumes after temperature falls below 140℃.

PCB Layout Guidelines

• Multi‑layer PCB helps suppress noise. Route input bypass capacitor to dedicated ground node to minimize power‑loop noise. Maximize copper area connecting thermal pad to GND plane for improved heat dissipation.

• SW is a fast‑switching node; keep SW traces short. Provide solid ground connection for IC GND pin.

• Place inductor and sense resistor RS close to respective IC pins. Minimize parasitic resistance on RS trace for accurate current sensing.

Q1: How do I set the maximum output current of PT4119E89E?
A: Output constant current is set by sense resistor RS between VIN‑CSN. Formula Iout=0.1/Rs (Rs≥0.082Ω). Using a 1% precision sense resistor achieves ±3% constant‑current accuracy.

Q2: What dimming modes are supported by the DIM pin?
A: The 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 preserves LED chromaticity with maximum dimming frequency up to 20kHz.

Q3: What are the differences between the two PT4119E89E packages?
A: SOT89‑5 is compact for space‑constrained low‑power boards. ESOP8 features exposed thermal pad for better heat dissipation and suits high‑power LED‑driver designs. Electrical specifications are identical; only package form and reel quantity differ.

Q4: How to handle thermal‑shutdown events on PT4119E89E?
A: Check input‑output voltage headroom. Optimize PCB copper‑pour thermal dissipation and ensure thermal pad is grounded. Verify inductor saturation‑current rating and Schottky‑diode leakage / voltage rating. Thermal‑shutdown triggers at 160℃ and auto‑recovers at 140℃.

Q5: Will an LED open‑load condition damage the chip?
A: The IC has built‑in LED open‑circuit protection. It enters safe low‑power mode under open‑load conditions and automatically resumes normal operation after load recovery.