MAX11800–MAX11803
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
22
______________________________________________________________________________________
TOUCH DETECT
PUR MODE
(OPTIONAL)
PUF MODE
SCAN MODE
MEASUREMENT COMPLETE—
DATA IS KNOWN
POWER ASSISTED PULLUP PERIOD (10
Ω)
PANEL IS ALLOWED TO RESETTLE BEFORE
DETERMINING DATA VALIDITY
IS THERE A TOUCH?
YES = LPM.
NO = TDM.
MEASUREMENT COMPLETE—
DATA IS KNOWN
PANEL IS ALLOWED TO RESETTLE BEFORE DETERMINING DATA VALIDITY
(THROUGH 50k
Ω/100kΩ PULLUP)
IS THERE A TOUCH?
YES = LPM.
NO = TDM.
DATA VALIDITY IS DETERMINED
(DATA IS TAGGED)
DATA VALIDITY IS DETERMINED
(DATA IS TAGGED)
INITIAL INPUT VOLTAGE
DETERMINED BY LAST SCAN
ACTIVITY
INITIAL INPUT VOLTAGE
DETERMINED BY LAST SCAN
ACTIVITY
FORCED FAST PULLUP USING
10
Ω SWITCH
TOUCH NOT PRESENT: TSC INPUT
REMAINS HIGH
TOUCH PRESENT:
TSC INPUT PULLED LOW
TOUCH NOT PRESENT:
TSC INPUT PULLED HIGH THROUGH 50k
Ω/100kΩ PULLUP
TOUCH PRESENT:
TSC INPUT PULLED LOW BY PANEL
TIME
TSC
INPUT
DIGITAL WAVEFORM
ANALOG WAVEFORM
TIME
DIGITAL WAVEFORM
ANALOG WAVEFORM
NORMAL TOUCH DETECTION
(NOTE: NO PUR PERIOD; ALLOW LONG PULLUP TIMES)
FAST PULLUP TOUCH DETECTION
(NOTE: INCREASED CURRENT IN PUR MODE DURING TOUCH)
VDD
TSC
INPUT
VDD
TOUCH DETECT
PUF MODE
SCAN MODE
Figure 7. Touch-Detection Operations