• Seven LED Driver Outputs: On, Off, Blinking, Fading at Programmable Rates
• Open-Drain Outputs Directly Drive LEDs to 40 mA Max
• Can Be Configured Into Two Independent Banks of LED Drivers
• Widely Programmable Blink Rates, Fade-On and Fade-Off Rates and Maximum Intensity
• LED Intensity Set Using Pulse Width Modulation (PWM)
• Outputs Not Used as LED Drivers Can Be Used as Regular General-Purpose Open-Drain Outputs
• 16 Steps of Maximum Intensity Control from Fully-Off to Fully-On States
• 256 Intensity Levels During Fade-On or Fade-Off for Smooth Perceived Transition
• Operating Power-Supply Voltage Range of 1.65 V to 3.6 V
• EVM Available
• Schmitt-Trigger Action Allows Slow Input Transition and Better Switching Noise Immunity at the Inputs
  • Vhys = 0.18 V Typ at 1.8 V
  • Vhys = 0.25 V Typ at 2.5 V
  • Vhys = 0.33 V Typ at 3.3 V
• 5.5-V Tolerant Open-Drain Outputs
• Low Standby Current with Shutdown Capability for Additional Power Savings
• Internal Power-On Reset
• Internal Oscillator Requires No External Components
• Programmed Through I2C Bus Interface Logic Compatible With SMBus
• 400-kHz Fast I2C Bus
• Noise Filter on SCL/SDA Inputs
• No Glitch on Power Up
• Supports Hot Insertion
• ESD Protection Exceeds JESD 22
  • 2000-V Human-Body Model (A114-A)
  • 200-V Machine Model (A115-A)
  • 1000-V Charged-Device Model (C101)
• Latch-Up Performance Exceeds 100 mA Per JESD 78, Class II

DESCRIPTION/ORDERING INFORMATION

This 7-bit LED dimmer for the two-line bidirectional bus (I2C) is designed to control (or dim) LEDs via the I2C interface [serial clock (SCL), serial data (SDA)]. Without this device, the microprocessor or microcontroller must be actively involved in turning on and off the LEDs (per the required dimming rate), which uses valuable processor time and the overloads I2C bus. The TCA6507 alleviates this issue by limiting the number of operations required by the processor in blinking LEDs and, thus, helps to create a more efficient system.

This device can be used for driving LEDs and for general-purpose parallel output expansion. The TCA6507 has three Select registers (Select0, Select1 and Select2), which can be used to configure each LED output into one of seven different operating modes. At power on, the outputs are in high impedance.

When used to drive LEDs, the seven outputs can be configured into two banks of outputs (BANK0 and BANK1). Each bank of outputs can be independently controlled for dimming rate and intensity through the I2C bus. The dimming and blink rates are fully programmable. The intensity of each bank of LEDs is controlled by dynamically varying the duty cycle of the signal, which has a period of approximately 8 ms and a pulse rate of 125 times per second, driving the outputs. The TCA6507 has two independent dimming/blinking modules—PWM0 and PWM1—driven by a single internal oscillator that supports these features. PWM0 determines the characteristics of BANK0 and PWM1 determines the characteristics of BANK1.

The TCA6507 has a master intensity level known as the ambient light detection (ALD) value. The associated pulse width modulation (PWM) signal for this value is PWMALD. The TCA6507 can be programmed such that PWMALD overrides PWM0 or PWM1 so selected LEDs are on steadily at the master intensity level. Further, the TCA6507 can be programmed such that the ALD value can override the maximum intensity values for PWM0 and PWM1. Thus, the ALD value can control the brightness of all LEDs whether they are on steadily or controlled by one of the dimming modules. The ALD value is stored in the lower four bits of the One-Shot / Master Intensity register.

When the I2C bus is idle, and intensity control is not used, the TCA6507 can be put into shutdown mode by setting the enable (EN) pin low. This mode provides additional power savings, as it is a low-power mode where the LEDs are off. A low signal on the EN pin also resets the registers and I2C/SMBus state machine in the TCA6507 to their default state.

An initial setup command must be sent from the I2C master to the TCA6507 to program the dimming rate and intensity (and intensity ramp if needed) for each bank of outputs. From then on, only one command from the bus master is required to turn each individual output ON, OFF, or to cycle at the programmed dimming rate. The default value for all time parameters is 256 ms so the default blink rate is approximately one per second.

The TCA6507 is optimized for 1.65 V to 3.6 V on the SDA/SCL side, but the LEDs can be driven by any voltage up to 5.5 V. This allows the TCA6507 to interface with next-generation microprocessors and microcontrollers, where supply levels are dropping down to conserve power.

This LED dimmer supports hot insertion.