AFE4490 datasheet(32/69 Pages) TI

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LED

Current

Control

8-Bit Resolution

LED2 Current

Reference

LED1 Current

Reference

H-Bridge

Driver

H-Bridge

LED2_ON

LED1_ON

LED2_ON

LED1_ON

LED2 Current Reference

LED1 Current Reference

3.3-V Supply

ILED

CBULK

H-Bridge Supply

External

Supply

AFE4400

SBAS601D – DECEMBER 2012 – REVISED MAY 2013

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TRANSMIT SECTION

The transmit section integrates the LED driver and the LED current control section with 8-bit resolution. This

integration is designed to meet a dynamic range of better than 105 dB (based on a 1-sigma LED current noise).

The LED2 and LED1 reference currents can be independently set. The current source (ILED) locally regulates and

ensures that the actual LED current tracks the specified reference.

Two LED driver schemes are supported:

•

An H-bridge drive for a two-terminal back-to-back LED package, as shown in Figure 46. The minimum H-

bridge supply voltage must be 2.5 V + (maximum voltage drop across the LED).

•

A push-pull drive for a three-terminal LED package; see Figure 47. The minimum external supply voltage =

2.0 V + (maximum voltage drop across the LED).

Figure 46. Transmit: H-Bridge Drive

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AFE4490 Datasheet(PDF) 32 Page - Texas Instruments