Datasheet

MAX7370
8 x 8 Key-Switch Controller and LED Driver/GPIOs
with I2C Interface and High Level of ESD Protection
14Maxim Integrated
• Putthepartintosleepmodetocauseallportstofade
out. Changing an individual PWM intensity during
fade out automatically cancels that port’s fade and
immediately turns off.
LED PWM
Each port has an individual PWM ratio register. The value
stored in this register configures the number of cycles
out of 255 that the output is sinking current (LED is on).
Setting a value of 0xFF in an individual intensity register
sets the output to continuously sink current (always on).
Conversely, setting a value of 0x00 in an individual inten-
sity register sets the output in a high-impedance state
(always off).
For applications requiring multiple ports to have the
same intensity, the common PWM ratio intensity setting
can be used in lieu of the individual intensity setting. To
use the common intensity setting, program bit D5 of the
corresponding port’s configuration register to logic-high.
Setting a port to use the common PWM ratio setting
copies the value of the common intensity register into
the individual intensity register at the beginning of each
PWM cycle. This allows an output port to be seamlessly
changed from common intensity to individual intensity
with no interruption in the PWM cycle.
Outputs are configured to sink a constant current of either
10mA or 20mA during the period of time when the output
is on. The setting in the individual GPIO constant-current
setting register (0x43) controls the value of the current.
LED Blink
Each LED driver-supported port has its own blink-control
settings through registers 0x54 to 0x57. See Table 30.
The blink period ranges from 0 (blink disabled) to 4.096s.
Settable blink duty cycles range from 6.25% to 50%. All
blink periods start at the same PWM cycle for synchro-
nized blinking between multiple ports.
Each port has its own counter to generate blink timing.
The blink counter can be programmed to cause the out-
put to gate off and on at a programmable rate. The blink
period can be set to 256ms, 512ms, 1.024s, 2.048s, or
4.096s using D[4:2] of the port’s individual configuration
register. The percentage of time that the LED is on for
one blink cycle is set to 50%, 25%, 12.5%, or 6.25% by
D[1:0] of the individual configuration register.
Interrupts
Three possible sources generate INT: key-switch FIFO
level/debounce cycle settings, I
2
C timeout, or GPIOs
configured as inputs (registers 0x03, 0x48, 0x5A, and
0x5B). Read the respective data/status registers for each
type of interrupt to clear INT. If multiple sources generate
the interrupt, all the related status registers must be read
to clear INT.
Serial Interface
Figure 1 shows the two-wire serial interface timing details.
Figure 1. Two-Wire Serial Interface Timing Details
SDA
SCL
t
HD, STA
t
LOW
t
HIGH
t
R
t
F
t
SU, DAT
t
SU, STA
t
SU, STO
t
BUF
t
HD, STA
t
HD, DAT
START
CONDITION
STOP
CONDITION
START
CONDITION
REPEATED
START CONDITION
t
F
t
F, TX
t
R