RT8475ZS - 350kHz LED Driver Buck/Boost Controller | Richtek
MPN: RT8475ZS ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0.85 | $0.85 |
| 10 | $0.72 | $7.20 |
| 100 | $0.58 | $58.00 |
| 500 | $0.49 | $245.00 |
| 1,000 | $0.42 | $420.00 |
RT8475ZS Overview
An LED driver controller is a power management IC that regulates current through one or more strings of LEDs, maintaining brightness uniformity and protecting the LEDs from overcurrent conditions. In the broader taxonomy, LED driver controllers belong to PMIC -> power management IC -> driver IC -> constant-current regulator -> semiconductor. By regulating current rather than voltage, these controllers compensate for variations in LED forward voltage (Vf), temperature drift, and aging, ensuring consistent lumen output across the operating range.
Key features of the RT8475ZS include its 350 kHz switching frequency, which keeps the converter above the AM band and allows compact inductor selection, and its dual topology flexibility (Buck or Boost) that lets a single part handle both step-down and step-up LED strings. The controller supports both analog dimming and PWM dimming, allowing brightness control from either a DC level or a duty-cycle signal for high-contrast dimming down to sub-1% levels. The 14-SOP package provides adequate thermal dissipation in surface-mount designs and supports standard reflow profiles.
The RT8475ZS uses Richtek's proprietary constant-current control architecture to regulate the high-side MOSFET switch current through an external sense resistor, achieving cycle-by-cycle current limiting. The 350 kHz oscillator is internally trimmed, eliminating the need for an external RT resistor, and the dual dimming inputs (ADIM and PDIM) interface easily to microcontrollers or analog reference voltages. A typical application circuit uses an N-channel MOSFET, a Schottky diode, an inductor, and a sense resistor to form a complete buck or boost LED driver capable of driving strings of 1 W to 5 W LEDs.
Typical applications include LED backlight drivers for LCD panels, architectural and decorative LED lighting, automotive interior lighting, and signage or indicator illumination. The wide input voltage tolerance of the controller supports both 12 V and 24 V bus systems commonly found in these applications. The analog dimming input is particularly useful for closed-loop feedback designs where ambient light sensing adjusts the LED current automatically.
When designing with the RT8475ZS, ensure that the external MOSFET, inductor, and sense resistor are chosen for the target LED string voltage and current. PCB layout should minimize the loop area of the power stage to reduce EMI and use a ground plane for stable operation. The PWM dimming frequency should be selected above 100 Hz to avoid visible flicker in lighting applications.
This page synthesizes distributor pricing, pin-compatible drop-in alternatives, and practical design notes for the RT8475ZS, providing engineering guidance that goes beyond the standard distributor product listing.
Drop-in alternatives for RT8475ZS — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with RT8475ZS (same form factor and footprint) — differing in Dimming Control, Switching Frequency, Topology.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
RT8475GS
✅ Drop-In ⚠️ Specs Unverified✓ In Stock
$0.2 / Unit
View Datasheet →RT8475ZS Maximum Ratings & Electrical Characteristics
| Topology | Step-Down (Buck), Step-Up (Boost) |
| Number of Outputs | 1 |
| Switching Frequency | 350 kHz |
| Dimming Control | Analog and PWM |
| Package Type | 14-SOP (3.90 mm body width) |
| Pin Count | 14 |
| Mounting Type | Surface Mount |
| Operating Mode | Constant-current controller |
| External Switch | Required (N-channel MOSFET) |
| Current Sense | External sense resistor |
| Output Type | PMIC LED Driver IC |
| RoHS Status | Compliant |
| Lead-Free | Yes |
RT8475ZS Pin Configuration
| Pin 1 | VIN — Input supply voltage |
| Pin 2 | GND — Ground |
| Pin 3 | CS — Current sense input |
| Pin 4 | ADIM — Analog dimming input |
| Pin 5 | PDIM — PWM dimming input |
| Pin 6 | RT — Oscillator timing resistor |
| Pin 7 | COMP — Loop compensation node |
| Pin 8 | FB — Feedback voltage input |
| Pin 9 | OVP — Over-voltage protection |
| Pin 10 | DRV — Gate driver output |
| Pin 11 | NC — Not connected (per datasheet) |
| Pin 12 | NC — Not connected (per datasheet) |
| Pin 13 | NC — Not connected (per datasheet) |
| Pin 14 | VCC — Internal regulator output |
Typical Applications
RT8475ZS is suitable for 6 applications: LED Backlight Driver for LCD Panels, Architectural and Decorative LED Lighting, Automotive Interior LED Lighting, LED Signage and Indicator Illumination, Portable LED Flashlight and Torch, Industrial Machine Vision LED Illumination.
LED Backlight Driver for LCD Panels
The RT8475ZS drives LED backlight strings in LCD panels used in industrial monitors, automotive displays, and consumer TVs. Its 350 kHz fixed switching frequency places fundamental switching noise above the AM band, simplifying EMI compliance for display modules. The dual-mode buck/boost topology lets the same controller serve low-voltage (below VIN) and high-voltage (above VIN) LED strings depending on the panel backlight architecture. With analog and PWM dimming inputs, the IC supports ambient-light-sensor feedback loops (analog) and high-contrast video-rate brightness modulation (PWM). A typical circuit uses an external N-channel MOSFET, a 22 µH inductor, a Schottky diode, and a sense resistor selected for the target LED current. Compared to discrete LED drivers, the controller-based approach offers better thermal distribution since power dissipation is shared between the IC and the external MOSFET.
Recommended
Architectural and Decorative LED Lighting
The RT8475ZS powers architectural LED lighting installations including cove lighting, accent strips, and decorative fixtures where constant-current regulation preserves color and brightness consistency across long LED runs. Its buck/boost flexibility supports a wide range of LED string voltages while keeping the input bus voltage standard (12 V or 24 V). PWM dimming at frequencies above 100 Hz ensures flicker-free operation suitable for camera and video recording environments, important for hospitality and stage lighting. The 14-SOP package supports standard reflow profiles for high-volume lighting fixture assembly. Compared to switching-capacitor LED drivers, the inductor-based buck/boost topology provides higher efficiency (typically 85-95%) at moderate LED currents, reducing thermal stress on the fixture housing.
Recommended
Automotive Interior LED Lighting
The RT8475ZS supports automotive interior LED lighting applications including dome lights, footwell illumination, instrument panel backlighting, and accent strips. The wide input voltage tolerance accommodates 12 V automotive battery systems with load-dump transients, and the 350 kHz switching frequency minimizes AM-band interference that could affect infotainment receivers. PWM dimming enables smooth fade-in/fade-out transitions for premium cabin lighting effects. The 14-SOP package is compatible with standard automotive PCB assembly processes. Note that the RT8475ZS is not explicitly AEC-Q100 qualified per available data, so design-in should include qualification review for production automotive programs. Compared to linear LED drivers, the switching topology reduces power dissipation in the fixture, lowering operating temperatures in enclosed automotive lamp housings.
Recommended
LED Signage and Indicator Illumination
The RT8475ZS drives LED signage applications including channel-letter signs, exit signs, and industrial indicator panels where constant brightness is critical for visibility. Its constant-current control architecture compensates for LED forward voltage variation and aging, maintaining uniform brightness across the sign face. The dual buck/boost topology supports both low-voltage (5 V) and high-voltage (24 V or 48 V) LED string configurations depending on the sign design. Analog dimming allows daylight-sensor integration for energy-saving auto-brightness adjustment. The 14-SOP package suits compact sign-driver PCBs behind channel letters. Compared to resistor-limited LED strings, the RT8475ZS-based driver delivers 20-40% energy savings and significantly longer LED lifetime by operating LEDs at controlled currents.
Recommended
Portable LED Flashlight and Torch
The RT8475ZS boosts or bucks battery voltage to drive high-power LED flashlights, headlamps, and portable work lights. The buck/boost topology supports a wide input voltage (e.g., 1S to 4S Li-Ion cells) while maintaining constant LED current regardless of battery discharge state. The 350 kHz switching frequency enables small inductor selection, important for compact flashlight form factors. PWM dimming supports multiple brightness modes (high, medium, low, strobe, SOS) commonly required in portable lighting. Compared to direct-drive LED circuits, the RT8475ZS-based driver extends battery runtime by maintaining efficiency across the discharge curve and prevents LED damage from current overshoot during battery connection.
Recommended
Industrial Machine Vision LED Illumination
The RT8475ZS drives LED ring lights, bar lights, and dome illuminators used in industrial machine vision systems for part inspection, barcode reading, and quality control. The constant-current control ensures consistent illumination intensity frame-to-frame, which is critical for reliable image processing. The 350 kHz switching frequency is well above typical machine vision camera frame rates (30-120 fps), avoiding flicker artifacts in captured images. The dual dimming interfaces support both manual brightness adjustment and automated feedback from image processing algorithms. Compared to constant-voltage LED drivers, the constant-current topology provides more uniform LED aging across the illuminator, extending calibration intervals in production environments.
Recommended
Recommended Products Summary
Engineering reference data for RT8475ZS — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | RT8475GS |
|---|---|---|
| Brand | Richtek | Richtek |
| Package | 14-SOP | SOP-16 |
| Switching Frequency | 350 kHz | 350 kHz |
| Topology | Buck, Boost | Buck, Boost |
| Dimming Control | Analog and PWM | Analog and PWM |
| Number of Outputs | 1 | 1 |
| Pin Count | 14 | 16 |
| Mounting Type | Surface Mount | Surface Mount |
Key Differentiators
- Dual buck/boost topology in one controller IC (vs RT8475GS)
- 350 kHz fixed switching frequency (vs RT8475GS)
- Dual analog and PWM dimming interfaces (vs RT8475GS)
Design Notes
Do not omit the external current-sense resistor. The RT8475ZS regulates LED current through the voltage across RSENSE, so a shorted or missing sense resistor will cause uncontrolled MOSFET current and possible LED or MOSFET damage. Select RSENSE using RSENSE = VSENSE / ILED, and ensure the sense resistor power rating is at least 2x the calculated dissipation for reliability.
Keep the power-stage loop area (MOSFET, Schottky diode, inductor) as small as possible to minimize EMI and prevent unstable switching behavior. Use a single ground plane with the RT8475ZS GND pin connected directly to the ground plane via a short trace. Place the input bypass capacitor within 2 mm of the VIN pin to suppress high-frequency noise injection.
While the RT8475ZS itself dissipates minimal power (it is a controller, not a switch), the external MOSFET and Schottky diode carry the LED current and dissipate the most heat. Select a MOSFET with low RDS(on) and a Schottky with low forward voltage to minimize power dissipation. For LED currents above 1 A, ensure the MOSFET and diode have adequate copper pour area or heatsinking.
Compliance Information
RoHS compliance confirmed per Richtek product page. AEC-Q100 status not confirmed in available data; verify with manufacturer for automotive designs.
