PCA9622_12 Datasheet, PDF (15/39 Pages) NXP Semiconductors – 16-bit Fm+ I2C-bus 100 mA 40 V LED driver

NXP Semiconductors
PCA9622
16-bit Fm+ I²C-bus 100 mA 40 V LED driver
Remark: During power-down, slow decay of voltage supplies may keep LEDs illuminated.
Consider disabling LED outputs using HIGH level applied to OE pin.
7.5 Power-on reset
When power is applied to V_DD, an internal power-on reset holds the PCA9622 in a reset
condition until V_DD has reached V_POR. At this point, the reset condition is released and the
PCA9622 registers and I²C-bus state machine are initialized to their default states (all
zeroes) causing all the channels to be deselected. Thereafter, V_DD must be lowered below
0.2 V to reset the device.
7.6 Software reset
The Software Reset Call (SWRST Call) allows all the devices in the I²C-bus to be reset to
the power-up state value through a specific formatted I²C-bus command. To be performed
correctly, it implies that the I²C-bus is functional and that there is no device hanging the
bus.
The SWRST Call function is defined as the following:
1. A START command is sent by the I²C-bus master.
2. The reserved SWRST I²C-bus address ‘0000 011’ with the R/W bit set to ‘0’ (write) is
sent by the I²C-bus master.
3. The PCA9622 device(s) acknowledge(s) after seeing the SWRST Call address
‘0000 0110’ (06h) only. If the R/W bit is set to ‘1’ (read), no acknowledge is returned to
the I²C-bus master.
4. Once the SWRST Call address has been sent and acknowledged, the master sends
2 bytes with 2 specific values (SWRST data byte 1 and byte 2):
a. Byte 1 = A5h: the PCA9622 acknowledges this value only. If byte 1 is not equal to
A5h, the PCA9622 does not acknowledge it.
b. Byte 2 = 5Ah: the PCA9622 acknowledges this value only. If byte 2 is not equal to
5Ah, then the PCA9622 does not acknowledge it.
If more than 2 bytes of data are sent, the PCA9622 does not acknowledge any more.
5. Once the right 2 bytes (SWRST data byte 1 and byte 2 only) have been sent and
correctly acknowledged, the master sends a STOP command to end the
SWRST Call: the PCA9622 then resets to the default value (power-up value) and is
ready to be addressed again within the specified bus free time (t_BUF).
The I²C-bus master must interpret a non-acknowledge from the PCA9622 (at any time) as
a ‘SWRST Call Abort’. The PCA9622 does not initiate a reset of its registers. This
happens only when the format of the SWRST Call sequence is not correct.
PCA9622
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 4 — 6 September 2012
© NXP B.V. 2012. All rights reserved.
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