LED driver ICs for automotive rear lamps

Overview | Key Features | Key Feature 1 | Key Feature 2 | Key Feature 3 | Key Feature 4 | Lineup

Industry's First! High 200mA output with high ±3% LED current accuracy

Overview

Automotive rear lamps are increasingly being configured with LEDs due to their longer life and lower power consumption. However, this has previously been difficult to achieve the level of reliability (including failsafe functionality and protection circuitry) and current accuracy required by automotive systems.
In response to this ROHM has developed the industry's first source drivers designed specifically for rear lamp applications. Multiple protection circuits are built in, along with high accuracy constant current blocks that minimize intensity variation. An early warning function is also included for greater safety and peace of mind.

When lamp demonstration is OFF and ON

Key Features

  1. 1ch source driver : Enables connection of 3 or 4 LEDs
  2. 200mA high current output
  3. High-accuracy LED current output to within ±3%
  4. Separate high / low LED current modes
  5. Built-in LED open / short protection
  6. Built-in unique P-Bus (Protect-Bus) function
BD8372HFP-M / EFJ-M Block Diagram
Demo board with
five BD8372HFP-M mounted
Package

Key Feature 1 : High accuracy (±3%) LED current control eliminates brightness variations.

Rear lamps require high-performance lights with no intensity variations, which depend on the tolerances of the LEDs and LED driver circuit. Discrete configuations consist of multiple parts that increase the amount of variation significantly, requiring sorting during production.
In contrast, ROHM's monolithic dedicated IC solutions integrate a high-performance constant current circuit featuring an industry-leading current accuracy of ±3%that, reduces manufacturing load.

LED Current Accuracy Comparison (3-LED Connection)

Key Feature 2 : Proprietary P-Bus (Protect-Bus) function built in

Although rear lamps come in many different configurations, most use around 20 LEDs. Since BD8372HFP-M and BD8372EFV-M can only drive 3-4 LEDs, multiple drivers are required. In these cases there is a risk of a single channel failing due to LED open and/or short-circuits. In order to ensure that all LEDs are turned OFF simultaneously in the event of failure (as an early warning to the driver for increased safety), ROHM integrates a unique P-BUS function that communicates with the other drivers when an abnormality is detected and turns OFF all LED lamps.

P-Bus (Protect Bus)

Key Feature 3 : Independent current settings for tail lamps and stop lamps

Rear lamps are designed to change in intensity during driving and braking operations. ROHM LED drivers for rear lamps feature a 2-stage current switching circuit for different current levels, depending on operation. In addition, with conventional LED drivers the current levels for tail lamp and stop lamp operation are fixed. ROHM, however, allows flexible adjustment of the light intensity based on requirements, facilitating design.

High/low current switching range

Key Feature 4 : LED open/short protection included

There is a possibility during driving that the LED board may become short-circuited or disconnected due to vibration. In order to prevent this ROHM integrates voltage and current monitoring circuits that will cut off LED current and notify the ECU of any abnormalities.

LED open/short protection included

Lineup

Part No. No. of
Channels
Maximum Output
Current
Dimming Mode Output Breakdown
Voltage
Package
BD8372HFP-M 1ch 200mA High Current /
Low Current
50V HRP7
BD8372EFJ-M 1ch 200mA High Current /
Low Current
50V HTSOP-J8

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