MAX6947 Maxim Integrated Products, MAX6947 Datasheet - Page 9

• Manufacturer Part Number: MAX6947
• Description: Constant-Current LED Drivers and I/O Expanders
• Manufacturer: Maxim Integrated Products

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Table 4. Individual Port Configuration Options (Port Output Registers 0x00–0x09)
The MAX6946/MAX6947 contain 10 I/O ports.
Configure the 10 I/O ports as logic inputs, open-drain
logic outputs, or constant-current sinks in any combina-
tion. Table 4 shows a detailed description of the indi-
vidual port configuration registers 0x00 through 0x09.
Use registers 0x00–0x09 to individually assign each
port as a logic input, open-drain logic output or con-
stant-current sink (see the PWM Intensity Control and
Figure 1. Simplified Schematic of I/O Ports
Low-logic
output
High-logic
output
Logic input
Constant-
current static
sink output
Constant-
current PWM
output
LED off
PORT TYPE
10-Port, Constant-Current LED Drivers and
INTERFACE
I/O Expanders with PWM Intensity Control
TO/FROM
SERIAL
REGISTER
0x03–0xFE
OUTPUT
_______________________________________________________________________________________
CODE
0x00
0x01
0x02
0xFF
OUTPUT CURRENT
GLOBAL CURRENT
OUTPUT PORT
Logic-high output with external pullup resistor; otherwise,
high impedance
8-BIT LATCH
1-BIT LATCH
3-BIT LATCH
RUN MODE (CONFIGURATION
0xFE = 254/256 PWM duty cycle
REGISTER
REGISTER
REGISTER
0x03 = 3/256 PWM duty cycle
Static constant-current sink
REGISTER BIT D0 = 1)
PORT COMMAND
Logic-high output with external pullup resistor;
READ I/O
output
MSB
Logic-low output, not constant current
I/O Ports
CLOSE SWITCH: 0x02–0xFE
POSITION A: 0x00–0x01
POSITION B: 0x02–0xFF
otherwise, high impedance
CMOS logic input
4-BIT DAC
GENERATOR
PWM
Phasing section). The I/O ports are high impedance
without V
power-up.
Figure 1 shows the I/O port structure of the MAX6946/
MAX6947. I/O ports P0 to P9 default to high impedance
on power-up, so LEDs or other port loads connected
draw no current. Ports used as inputs do not load their
source signals.
(CONFIGURATION REGISTER
CURRENT
ENABLE
SET
High impedance
SHUTDOWN
DD
BIT D0 = 0)
applied and remain high impedance upon
A
N
B
I/O PORT
Adjustable constant current
Full constant-current drive
unaffected by shutdown
APPLICATION NOTES
Lowest supply current,
with no PWM
LED off
9