MAX1608 Datasheet, PDF (11/16 Pages) Maxim Integrated Products – Octal SMBus-to-Parallel I/O Expanders

Octal SMBus-to-Parallel I/O Expanders
Table 3. Data Register 1 (NDR1 and SDR1) Bit Assignments (read or write)
POR STATE
BIT
NAME
MAX1608 MAX1609
FUNCTION
7
IO7
0
1
Sets IO7 state. 0 = on (low state), 1 = off (high-impedance).
6
IO6
0
1
Sets IO6 state. 0 = on (low state), 1 = off (high-impedance).
5
IO5
0
1
Sets IO5 state. 0 = on (low state), 1 = off (high-impedance).
4
IO4
0
1
Sets IO4 state. 0 = on (low state), 1 = off (high-impedance).
3
IO3
0
1
Sets IO3 state. 0 = on (low state), 1 = off (high-impedance).
2
IO2
0
1
Sets IO2 state. 0 = on (low state), 1 = off (high-impedance).
1
IO1
0
1
Sets IO1 state. 0 = on (low state), 1 = off (high-impedance).
0
IO0
0
1
Sets IO0 state. 0 = on (low state), 1 = off (high-impedance).
Table 4. Data Register 2 (NDR2 and SDR2) Bit Assignments (read or write)
BIT
NAME
POR STATE
FUNCTION
7
MASKH7
1
Masks IO7 low-to-high interrupt. 0 = interrupts, 1 = masked.
6
MASKH6
1
Masks IO6 low-to-high interrupt. 0 = interrupts, 1 = masked.
5
MASKH5
1
Masks IO5 low-to-high interrupt. 0 = interrupts, 1 = masked.
4
MASKH4
1
Masks IO4 low-to-high interrupt. 0 = interrupts, 1 = masked.
3
MASKH3
1
Masks IO3 low-to-high interrupt. 0 = interrupts, 1 = masked.
2
MASKH2
1
Masks IO2 low-to-high interrupt. 0 = interrupts, 1 = masked.
1
MASKH1
1
Masks IO1 low-to-high interrupt. 0 = interrupts, 1 = masked.
0
MASKH0
1
Masks IO0 low-to-high interrupt. 0 = interrupts, 1 = masked.
slave attempts to respond, bus arbitration rules apply,
with the lowest address code going first. The other
device(s) will not generate an acknowledge and will
continue to hold the ALERT pin low until it is allowed to
clear its own interrupt.
Clearing the interrupt has no effect on the state of the
status registers.
Input/Output Pins
Each IO_ pin is protected by an internal 20mA (typical)
current-limit circuit. Typical pull-down on-resistance at
V_CC = +2.7V and +5.5V is 100Ω and 66Ω, respectively.
When the IO_ is high impedance, it actually has a
0.5µA pull-down current source included as part of the
read-back functionality.
External pull-up resistors and IO_ sink capability can
affect the outputs’ rise and fall times. When using the
MAX1608/MAX1609 to control an external MOSFET in
power-switching applications, pull-up and/or series resis-
tance can be used together with the MOSFET’s gate
capacitance or additional external capacitance (Figure 6)
to control the transition time of the switched source.
The input logic levels are TTL compatible and are sam-
pled during a readback SMBus transmission (see RSB
register in Data Registers section ).
Power-On Reset
The MAX1608/MAX1609’s power-on-reset circuit
ensures that the IO_ states are defined when V+ is first
applied or when the supply dips below the UVLO
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