MAX1233_05 Datasheet, PDF (31/45 Pages) Maxim Integrated Products – ±15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller

±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
FORCE LINE
X+
SENSE LINE
MEASURE X-POSITION
Y+
TOUCH
V
X-POSITION
X-
FORCE LINE
Y-
OPEN CIRCUIT
HOST WRITES
ADC
CONTROL REGISTER
START CLOCK
SET BUSY
LOW
BATTERY INPUT 1 OR
BATTERY INPUT 2
SENSE LINE
MEASURE Z1-RESISTANCE
X+
FORCE LINE
Y+
TOUCH
V
Z1-RESISTANCE
X-
FORCE LINE
Y-
OPEN CIRCUIT
OPEN CIRCUIT
X+
FORCE LINE
Y+
IS ADC
NO
REFERENCE IN
AUTO POWER-DOWN
MODE?
YES
POWER UP REFERENCE
POWER UP
ADC
POWER DOWN
ADC
TOUCH
V
Z2-RESISTANCE
FORCE LINE X-
Y- _{SENSE LINE}
MEASURE Z2-RESISTANCE
Figure 13. Pressure Measurement Block Diagram
BATTERY
0.5V TO
6.0V
V_BAT
DC/DC
2.7V
CONVERTER
AV_DD
CONVERT
BATTERY INPUT 1 OR 2
NO
IS DATA
AVERAGING DONE?
YES
STORE BATTERY INPUT 1 OR 2 IN
BAT1 OR BAT2 REGISTER
POWER DOWN REFERENCE
SET BUSY HIGH
TURN OFF CLOCK
DONE
7.5kΩ
Figure 15. Battery Voltage-Reading Flowchart
0.125V TO 1.5V
CONVERTER
2.5kΩ
Figure 14. Battery Measurement Block Diagram
Battery-Voltage Monitors
Two dedicated analog inputs (BAT1 and BAT2) allow the
MAX1233/MAX1234 to monitor the battery voltages prior
to the DC/DC converter. Figure 14 shows the battery volt-
age monitoring circuitry. The MAX1233/ MAX1234 direct-
ly monitor battery voltages from 0.5V to 6V. An internal
resistor network divides down BAT1 and BAT2 by 4 so
that a 6V battery voltage results in a 1.5V input to the
ADC. To minimize power consumption, the divider is only
enabled during the sampling of BAT1 and BAT2. Figure
15 illustrates the process of battery input reading.
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