MAX7370 datasheet(14/37 Pages) MAXIM

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�� Maxim Integrated Products 14

MAX7370

8 x 8 Key-Switch Controller and LED Driver/GPIOs

with I2C Interface and High Level of ESD Protection

• Putthepartintosleepmodetocauseallportstofade

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

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, I2C 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

tHD, STA

tLOW

tHIGH

tSU, DAT

tSU, STA

tSU, STO

tBUF

tHD, STA

tHD, DAT

START

CONDITION

STOP

CONDITION

START

CONDITION

REPEATED

START CONDITION

tF, TX

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