L9985 - Automotive Quad Low-Side Driver | STMicroelectronics
MPN: L9985 ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $3.5 | $3.50 |
| 10 | $3.15 | $31.50 |
| 100 | $2.8 | $280.00 |
| 500 | $2.45 | $1,225.00 |
| 1,000 | $2.1 | $2,100.00 |
L9985 Overview
A low-side driver is a type of power switch that connects the load to ground when activated, with the load connected between the positive supply and the driver output. In automotive systems, low-side drivers are commonly used to control actuators, lamps, and relays, where the load is referenced to the battery positive rail. The L9985 belongs to the family of smart power switches, which integrate protection and diagnostic features to enhance system reliability.
Key features of the L9985 include four independent output channels, each capable of delivering up to 1.5 A continuous current, with a maximum supply voltage of 40 V. The device features overcurrent protection, thermal shutdown, and an open-load detection function, which are essential for automotive safety. Additionally, the L9985 provides a serial peripheral interface (SPI) for advanced diagnostics and control, allowing the microcontroller to monitor and configure each channel independently.
The L9985 utilizes ST's proprietary VIPower technology, which combines vertical current flow with intelligent power management, resulting in low on-resistance and efficient power dissipation. The PowerSO-20 package, with an exposed pad, ensures effective heat transfer to the PCB, enabling reliable operation at high ambient temperatures up to 150°C. The device is AEC-Q100 qualified, meeting the stringent quality and reliability standards required for automotive electronics.
Typical applications include automotive body control modules, lighting control, relay drivers, and solenoid drivers in transmission and braking systems. The L9985 is also suitable for industrial automation, where robust switching and diagnostic capabilities are required. Its SPI interface simplifies system integration, reducing the number of I/O pins needed on the microcontroller.
When designing with the L9985, it is crucial to ensure proper PCB layout for thermal management, especially when driving multiple channels at high current. The exposed pad should be connected to a large copper area to dissipate heat effectively. Additionally, the SPI interface requires careful attention to signal integrity and timing to avoid communication errors.
Drop-in alternatives for L9985 — 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 L9985 (same form factor and footprint) — differing in On-Resistance (per channel), Protection Features, Operating Temperature Range, Output Current per Channel, Package.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
L9986
✅ Drop-In ⚠️ Specs Unverified✓ In Stock
$1.85 / Unit
View Datasheet →TLE6228GP
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
VNQ5050AKTR
⚡ Same Package ⚠️ Specs Unverified✓ In Stock
$2.27 / Unit
View Datasheet →L9985 Maximum Ratings & Electrical Characteristics
| Number of Channels | 4 |
| Output Current per Channel | 1.5 A |
| Supply Voltage Range | 5.5 V to 40 V |
| On-Resistance (per channel) | 0.5 ohm |
| Operating Temperature Range | -40C to +150C |
| Package | PowerSO-20 |
| Mounting Type | Surface Mount |
| Interface | SPI |
| Protection Features | Overcurrent, Thermal Shutdown, Open-Load Detection |
| AEC-Q100 Qualified | Yes |
| RoHS Compliant | Yes |
| Output Type | Low-Side |
| Diagnostic Output | SPI |
L9985 Pin Configuration
| Pin 1 | OUT1 — Output channel 1 |
| Pin 2 | OUT2 — Output channel 2 |
| Pin 3 | OUT3 — Output channel 3 |
| Pin 4 | OUT4 — Output channel 4 |
| Pin 5 | GND — Ground |
| Pin 6 | VCC — Supply voltage |
| Pin 7 | SCK — SPI clock |
| Pin 8 | SDI — SPI data input |
| Pin 9 | SDO — SPI data output |
| Pin 10 | CS — Chip select |
| Pin 11 | GND — Ground |
| Pin 12 | VCC — Supply voltage |
| Pin 13 | OUT1 — Output channel 1 (duplicate) |
| Pin 14 | OUT2 — Output channel 2 (duplicate) |
| Pin 15 | OUT3 — Output channel 3 (duplicate) |
| Pin 16 | OUT4 — Output channel 4 (duplicate) |
| Pin 17 | GND — Ground |
| Pin 18 | VCC — Supply voltage |
| Pin 19 | NC — Not connected |
| Pin 20 | NC — Not connected |
Typical Applications
L9985 is suitable for 6 applications: Automotive Body Control Module, Lighting Control, Relay Driver, Solenoid Driver, Industrial Automation, Motor Control.
Automotive Body Control Module
The L9985 is used in body control modules to drive relays, lamps, and solenoids. Its four channels can control multiple loads, while the SPI interface provides diagnostics for fault detection. The wide supply voltage range (5.5 V to 40 V) accommodates automotive battery voltage variations, and the AEC-Q100 qualification ensures reliability in harsh environments. The device's overcurrent and thermal protection prevent damage to the module and loads.
Recommended
Lighting Control
The L9985 can drive automotive lighting loads such as headlamps, tail lamps, and interior lights. Each channel can handle up to 1.5 A, sufficient for most incandescent bulbs. The open-load detection feature identifies burnt-out bulbs, enabling fault reporting to the ECU. The device's low on-resistance minimizes power loss, and the thermal shutdown protects against overload conditions.
Recommended
Relay Driver
The L9985 is ideal for driving relays in automotive and industrial systems. Each channel can drive a relay coil with a holding current of up to 1.5 A, and the built-in freewheeling diode protection (if external) handles inductive kickback. The SPI interface allows the microcontroller to control relay states and read diagnostic information, such as open-load or overcurrent faults. The device's robust design ensures reliable operation in high-vibration environments.
Recommended
Solenoid Driver
The L9985 can drive solenoids in transmission, braking, and industrial automation systems. The device's high current capability (1.5 A per channel) and thermal protection make it suitable for continuous operation. The SPI interface enables precise control and monitoring of solenoid states, while the open-load detection ensures the solenoid is connected. The wide supply voltage range accommodates various system voltages.
Recommended
Industrial Automation
In industrial automation, the L9985 is used to switch loads such as valves, actuators, and indicators. Its robust protection features (overcurrent, thermal shutdown) ensure safe operation in harsh environments. The SPI interface allows integration with PLCs or microcontrollers for centralized control and diagnostics. The PowerSO-20 package with exposed pad facilitates heat dissipation, enabling reliable operation at high ambient temperatures.
Recommended
Motor Control
The L9985 can be used to drive small DC motors in automotive and industrial applications, such as window lifts, seat adjusters, and fans. Each channel can handle up to 1.5 A, sufficient for small motors. The device's low on-resistance reduces power loss, and the thermal shutdown protects against overload. The SPI interface enables speed control via PWM and provides diagnostic feedback.
Recommended
Recommended Products Summary
Engineering reference data for L9985 — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | L9986 | TLE6228GP | VNQ5050AK |
|---|---|---|---|---|
| Package | PowerSO-20 | PowerSO-20 | PowerSO-20 | PowerSO-20 |
| Brand | STMicroelectronics | STMicroelectronics | Infineon | STMicroelectronics |
| Output Current per Channel | 1.5 A | 2 A | 1.5 A | 0.5 A |
| Supply Voltage Range | 5.5 V to 40 V | 5.5 V to 40 V | 5.5 V to 40 V | 4.5 V to 36 V |
| Interface | SPI | SPI | SPI | SPI |
| Output Type | Low-Side | Low-Side | Low-Side | High-Side |
| AEC-Q100 Qualified | Yes | Yes | Yes | Yes |
| On-Resistance | 0.5 ohm | 0.4 ohm | 0.5 ohm | 0.8 ohm |
Key Differentiators
- Lower on-resistance (0.5 ohm) compared to VNQ5050AK (0.8 ohm) (vs VNQ5050AK)
- Higher output current (1.5 A per channel) than VNQ5050AK (0.5 A) (vs VNQ5050AK)
- Same package and pinout as L9986, allowing easy upgrade path (vs L9986)
Design Notes
The L9985 in PowerSO-20 package can dissipate significant power when driving multiple channels at high current. For example, at 1.5 A per channel with 0.5 ohm on-resistance, each channel dissipates 1.125 W, totaling 4.5 W for all four channels. Ensure the exposed pad is soldered to a large copper area on the PCB to keep the junction temperature below the maximum rating. Use thermal vias to enhance heat transfer to the ground plane.
Place decoupling capacitors (100 nF and 10 uF) close to the VCC and GND pins to suppress noise and ensure stable operation. For the SPI interface, keep the traces short and avoid routing them near high-current switching lines to prevent signal integrity issues. Use a ground plane to minimize loop area and reduce EMI.
When driving inductive loads such as relays or solenoids, always connect a freewheeling diode across the load to clamp the inductive kickback voltage. The L9985 does not have internal clamping diodes, so external protection is mandatory to prevent damage to the output transistors. Additionally, ensure the SPI communication is properly initialized before enabling any output channel to avoid unintended switching.
Compliance Information
AEC-Q100 qualified per STMicroelectronics. RoHS compliant. Halogen-free status not specified in available data.
