Datasheet

LTC2977
21
2977fa
For more information www.linear.com/LTC2977
Device Address
The I
2
C/SMBus address of the LTC2977 equals the base
address + N where N is a number from 0 to 8. N can be
configured by setting the ASEL0 and ASEL1 pins to V
DD33
,
GND or FLOAT. See Table 1. Using one base address and
the nine values of N, nine LTC2977s can be connected
together to control 72 outputs. The base address is stored
in the MFR_I2C_BASE_ADDRESS register. The base ad
-
dress can be written to any value, but generally should not
Table 1. LTC2977 Device Address Look-Up Table
ADDRESS
DESCRIPTION
HEX DEVICE
ADDRESS BINARY DEVICE ADDRESS BITS ADDRESS PINS
7-Bit 8-Bit 6 5 4 3 2 1 0 R/W ASEL1 ASEL0
Alert Response 0C 19 0 0 0 1 1 0 0 1 X X
Global 5B B6 1 0 1 1 0 1 1 0 X X
N = 0 5C* B8 1 0 1 1 1 0 0 0 L L
N = 1 5D BA 1 0 1 1 1 0 1 0 L NC
N = 2 5E BC 1 0 1 1 1 1 0 0 L H
N = 3 5F BE 1 0 1 1 1 1 1 0 NC L
N = 4 60 C0 1 1 0 0 0 0 0 0 NC NC
N = 5 61 C2 1 1 0 0 0 0 1 0 NC H
N = 6 62 C4 1 1 0 0 0 1 0 0 H L
N = 7 63 C6 1 1 0 0 0 1 1 0 H NC
N = 8 64 C8 1 1 0 0 1 0 0 0 H H
H = Tie to V
DD33
, NC = No Connect = Open or Float, L = Tie to GND, X = Don’t Care
*MFR_I2C_BASE_ADDRESS = 7bit 5C (Factory Default)
be changed unless the desired range of addresses overlap
existing addresses. Watch that the address range does not
overlap with other I
2
C/SMBus device or global addresses,
including I
2
C/SMBus multiplexers and bus buffers. This
will bring you great happiness.
The LTC2977 always responds to its global address and the
SMBus Alert Response address regardless of the state of
its
ASEL pins and the MFR_I2C_BASE_ADDRESS register.
OPERATION