Detailed Description
The MAX6946/MAX6947 general-purpose input/output
(GPIO) peripherals provide 10 I/O ports, P0 to P9, con-
trolled through an I
2
C-compatible serial interface. Use
the 10 I/O ports as logic inputs, open-drain logic out-
puts, or constant-current sinks in any combination.
Ports withstand 7V independent of the MAX6946/
MAX6947s’ supply voltage whether used as logic
inputs, logic outputs, or constant-current sinks.
The MAX6946/MAX6947 feature shutdown and standby
modes for low-power dissipation. The I/O ports feature
pulse-width modulation (PWM) of the outputs and can
stagger the PWM timing of the 10 port outputs in con-
secutively phased 45° increments. The I/O ports also
feature ramp-up and ramp-down controls.
The MAX6946/MAX6947 feature a RST input to halt any
serial-interface transmission and bring the device out of
shutdown.
Open-drain logic outputs require external pullup resis-
tors to provide the logic-high reference. Ports config-
ured as open-drain logic outputs have a relatively weak
sink capability, but are still adequate for normal logic-
level outputs. The weak drive means that the short-cir-
cuit current is low enough that inadvertently driving an
LED from a port configured as a logic output is unlikely
to damage the LED.
The MAX6946 features a fixed I
2
C slave address of
010 0000 and provides an OSC input to accept an
external PWM clock input as an alternative to the inter-
nal PWM clock.
The MAX6947 features an AD0 input that uses two-level
logic to select from two I
2
C slave addresses. The
MAX6947 always uses the internal PWM clock.
Register Structure
The MAX6946/MAX6947 contain 22 internal registers
(see Table 1). Use registers 0x00 to 0x09 to individually
control ports P0 to P9. Registers 0x0A to 0x0D allow
more than one port control register to be written with
the same data to simplify software. Registers 0x0E and
0x0F do not store data, but return the port input status
when read. Registers 0x10 to 0x15 configure and con-
trol the device operation.
MAX6946/MAX6947
10-Port, Constant-Current LED Driver and
I/O Expander with PWM Intensity Control
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Table 1. Register Address Map
Port P0 output level or PWM 0x00 0x01
Port P1 output level or PWM 0x01 0x02
Port P2 output level or PWM 0x02 0x03
Port P3 output level or PWM 0x03 0x04
Port P4 output level or PWM 0x04 0x05
Port P5 output level or PWM 0x05 0x06
Port P6 output level or PWM 0x06 0x07
Port P7 output level or PWM 0x07 0x08
Port P8 output level or PWM 0x08 0x09
Port P9 output level or PWM 0x09 0x10
Write ports P0–P9 with same
output level or PWM
