STMPE1801BJR STMicroelectronics, STMPE1801BJR Datasheet - Page 37

• Manufacturer Part Number: STMPE1801BJR
• Description: Touch Screen Converters & Controllers Xpander Logic 18-Bit 18 GPIO 1.65 to 3.6V
• Manufacturer: STMicroelectronics

Specifications of STMPE1801BJR

• Rohs: yes
• Input Type: 1 Keypad
• Data Rate: 400 kbps
• Resolution: 18 bit
• Interface Type: I2C
• Supply Voltage: 1.65 V to 3.6 V
• Supply Current: 28 uA
• Operating Temperature: - 40 C to + 85 C
• Package / Case: CSP-25
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT
• Supply Voltage - Max: 3.6 V
• Supply Voltage - Min: 1.65 V

STMPE1801
4.
The key detection sequence is described below:
1.
2.
3.
4.
5.
This eliminates the need to drive columns that do not have any key press. This in turn
reduces the switching amount and hence the reduction in noise and EMI.
Also the 4 mA IO during GPIO mode is 1 mA in keypad mode.
key-press ROW. This is because the row and column node of key press are shorted
together.
The state machine continues to poll while the key is still pressed and is reinitialized
once all the keys are released.
The column outputs are initially not driven.
Then the row inputs are checked for any special function keys.
Next, the columns are checked for any normal key presses.
With the internal pull-down resistor on the columns, the column senses a logic low. But
when there is a normal key press, the pull up on the row and pull down on the column
forms a resistor voltage divider. Since the pull up resistor is sized much smaller than
the pull down resistor, the voltage on the column is pulled to logic high state.
Then only the configured columns that sensed a high are driven low in turn and check
for normal key presses.
Doc ID 17884 Rev 3
Keypad controller
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