OZ9956B is a high-efficiency multi-string LED backlight controller IC designed for notebook and LCD panel applications.

Function: Six String LED Controller

Package: 20-QFN Type

Manufacturer: O2Micro International

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Description

OZ9956B is a high efficiency, DC/DC controller that drives up to six (6) strings of LEDs in parallel configuration, with multiple LEDs in each string connected in series. It is targeted for notebook/netbook applications.

It provides six (6) LED current sense inputs in an “OR” configuration for improved backlight reliability. This allows the backlight to remain functional in the event that any string (s) is damaged during normal operation.

OZ9956B can receive either an analog signal or an external Pulse Width Modulation (PWM) signal for the dimming control function. This IC provides an integrated circuit to balance the current flow through each LED string, as well as, the integrated power MOSFET.

It integrates a DC/DC converter controller with an internal power MOSFET and supports up to six parallel LED strings, each consisting of multiple series-connected LEDs. The device ensures uniform brightness and enhanced reliability through current balancing and fault-tolerant architecture.

Features

• Supports up to 6 LED strings in parallel
• Integrated DC/DC converter controller
• Built-in power MOSFET (reduced external components)
• High-frequency switching operation
• Integrated LED current balancing circuit
• Analog and PWM dimming control support
• “OR” configured current sense inputs for fault tolerance
• Over-voltage protection (OVP)
• Over-current protection (OCP)

Pinout

Key Functional Characteristics

• Each LED string current is independently sensed and regulated
• If one string fails (open/short), remaining strings continue operation
• Automatic current balancing ensures uniform brightness across all strings
• High efficiency due to integrated switching MOSFET and optimized control loop

Architecture Overview

• Boost-type DC/DC converter topology commonly used
• Internal MOSFET switches energy through an external inductor
• Output voltage automatically adjusts based on LED string requirements
• Feedback loop maintains constant current per string rather than constant voltage

Dimming Control

• Analog dimming: Adjusts LED current amplitude directly
• PWM dimming: Controls perceived brightness via duty cycle modulation
• Wide dimming range suitable for display backlight applications

Protection Features

• Over-voltage protection prevents damage during open LED conditions
• Over-current protection safeguards IC and LEDs
• Fault-tolerant operation via OR-connected current sense scheme

Design Notes

• Inductor and switching frequency selection directly impact efficiency and EMI
• Ensure proper layout for current sense lines to minimize noise
• Thermal management is critical due to integrated MOSFET losses
• Compensation network tuning required for stable control loop
• Careful LED string matching improves overall brightness uniformity

How to Choose This IC

• Ideal for multi-string LED backlight designs requiring redundancy
• Suitable when compact design is needed (integrated MOSFET)
• Choose based on LED string count (≤6 strings)
• Consider thermal and efficiency trade-offs vs. external MOSFET solutions

Typical Applications

• Notebook / Netbook LCD backlight
• LED display panels
• Industrial display backlighting
• Portable device lighting systems

Alternative / Equivalent Products

• OZ9966 (higher integration variant)
• TPS61187 (Texas Instruments multi-string LED driver)
• BD9479 (ROHM LED backlight driver)
• MP3394 (Monolithic Power Systems multi-string controller)

Other data sheets are available within the file: GB98A, OZ521, OZ522, OZ523, OZ524

OZ9956B Datasheet PDF Download