TCA6507_16 Datasheet, PDF (15/45 Pages) Texas Instruments – Low-Voltage 7-Bit I2C and SMBus LED Driver

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TCA6507
SCPS164C – MAY 2007 – REVISED JANUARY 2016
8.4 Device Functional Modes
8.4.1 Power-On Reset
When power (from 0 V) is applied to V_CC, an internal power-on reset holds the TCA6507 in a reset condition until
V_CC has reached V_POR. At that point, the reset condition is released, and the TCA6507 registers and I²C/SMBus
state machine initialize to their default states.
After the initial power-up phase, V_CC must be lowered to below 0.2 V, and then back up to the operating voltage
(V_CC) for a power-reset cycle.
8.4.2 Enable and Reset
If the enable (EN) input is set to low, the TCA6507 is put in the standby or shutdown mode. In this mode, the
oscillator is turned off, the registers are returned to their default state, and the I²C/SMBus state machine is
initialized. This mode is useful for low-power consumption. An internal filtering circuit prevents negative glitches
from accidentally shutting down the device. EN must be low for a minimum of approximately 60 μs to ensure a
shutdown state.
The system master can reset the TCA6507 in the event of a timeout or other improper operation by setting
EN low for a minimum of approximately 60 μs. This has the same effect as a power-on reset without powering-
down the TCA6507.
The oscillator start up time (t_OSC) is measured from the point when EN is set high.
8.5 Programming
8.5.1 I²C Interface
The TCA6507 has a standard bidirectional I²C interface that is controlled by a master device to be configured or
read the status of this device. Each slave on the I²C bus has a specific device address to differentiate between
other slave devices that are on the same I²C bus. Many slave devices require configuration upon startup to set
the behavior of the device. This is typically done when the master accesses internal register maps of the slave,
which have unique register addresses. A device can have one, or multiple registers where data is stored, written,
or read.
The physical I²C interface consists of the serial clock (SCL) and serial data (SDA) lines. Both SDA and SCL lines
must be connected to V_CC through a pullup resistor. The size of the pullup resistor is determined by the amount
of capacitance on the I²C lines. (For further details, refer to I²C Pullup Resistor Calculation (SLVA689).) Data
transfer may be initiated only when the bus is idle. A bus is considered idle if both SDA and SCL lines are high
after a STOP condition.
The following is the general procedure for a master to access a slave device:
1. If a master wants to send data to a slave:
– Master-transmitter sends a START condition and addresses the slave-receiver
– Master-transmitter sends data to slave-receiver
– Master-transmitter terminates the transfer with a STOP condition
2. If a master wants to receive or read data from a slave:
– Master-receiver sends a START condition and addresses the slave-transmitter
– Master-receiver sends the requested register to read to slave-transmitter
– Master-receiver receives data from the slave-transmitter
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