Applications Information
Output Level Translation
The open-drain output architecture allows the ports to
level translate the outputs to higher or lower voltages
than the MAX7313 supply. An external pullup resistor
can be used on any output to convert the high-imped-
ance logic-high condition to a positive voltage level.
The resistor can be connected to any voltage up to
5.5V. For interfacing CMOS inputs, a pullup resistor
value of 220kΩ is a good starting point. Use a lower
resistance to improve noise immunity, in applications
where power consumption is less critical, or where a
faster rise time is needed for a given capacitive load.
Compatibility with MAX7311
The MAX7313 is pin compatible and software compatible
with the standard register structure used by MAX7311,
PCA9535, and PCA9555. However, some MAX7311 func-
tions are not implemented in the MAX7313, and the
MAX7313’s PWM and blink functionality is not supported
in the MAX7311. Software compatibility is clearly not
100%, but the MAX7313 was designed so the subset
(omitted) features default to the same power-up behavior
as the MAX7311, PCA9535, and PCA9555, and superset
features do not use existing registers in a different way. In
practice, many applications can use the MAX7313 as a
drop-in replacement for the MAX7311.
Driving LED Loads
When driving LEDs, a resistor in series with the LED
must be used to limit the LED current to no more than
50mA. Choose the resistor value according to the fol-
lowing formula:
R
LED
= (V
SUPPLY
- V
LED
- V
OL
) / I
LED
MAX7313
16-Port I/O Expander with LED Intensity
Control and Interrupt
______________________________________________________________________________________________________ 21
Table 13. Master, O16 Intensity Register
REGISTER DATA
REGISTER
ADDRESS
CODE
(HEX)
D7 D6 D5 D4 D3 D2 D1 D0
MSB LSB MSB LSB
MASTER AND GLOBAL INTENSITY
R/W
MASTER INTENSITY GLOBAL INTENSITY
Write master and global intensity 0
Read back master and global intensity 1
M3 M2 M1 M0 G3 G2 G1 G0
Master intensity duty cycle is 0/15 (off);
internal oscillator is disabled;
all outputs will be static with no PWM
— 0000————
Master intensity duty cycle is 1/15 — 0001————
Master intensity duty cycle is 2/15 — 0010————
Master intensity duty cycle is 3/15 — 0011————
— — ————————
Master intensity duty cycle is 13/15 — 1101————
Master intensity duty cycle is 14/15 — 1110————
Master intensity duty cycle is 15/15 (full) — 1111————
O16 intensity duty cycle is 1/16 — ———— 0000
O16 intensity duty cycle is 2/16 — ———— 0001
O16 intensity duty cycle is 3/16 — ———— 0010
— — ————————
O16 intensity duty cycle is 14/16 — ———— 1101
O16 intensity duty cycle is 15/16 — ———— 1110
O16 intensity duty cycle is 16/16
(static output, no PWM)
—
0X0E
———— 1111
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