MAX11803 Maxim Integrated Products, MAX11803 Datasheet - Page 26

• Manufacturer Part Number: MAX11803
• Description: (MAX11800 - MAX11803) Ultra-Small Resistive Touch-Screen Controllers
• Manufacturer: Maxim Integrated Products

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Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I
The EINT mode reduces TIRQ activity. During EINT, the
MAX11800–MAX11803 idle in a TDM. TIRQ goes low
when a new touch is detected on the panel. TIRQ stays
low for a fixed duration as specified in the configuration
register 0x01, indicating to the AP that a touch is pre-
sent and measurements are required.
The AP requests specific panel setups and measure-
ments through the serial interface using panel setup
and conversion commands after TIRQ goes low. Once
a measurement is complete (with CONT = 0), the
MAX11800–MAX11803 check for the continued pres-
ence of a touch and tag the data accordingly. See
Table 7. The duration of this operation is programma-
ble, specified in the Touch-Detect Pullup Timing
Configuration Register (0x07) section. After the data is
tagged, it is available for readback through the serial
interface. The MAX11800–MAX11803 do not return to
TDM when the panel touch is still present (ETAG = 00,
01), but remain in an LPM awaiting further measure-
ment commands. The devices return to TDM when the
panel touch is no longer present (ETAG = 10) and
return control of the TIRQ interrupt to the TDM circuitry
to await the next touch event.
After a touch is indicated, the AP must continue to issue
conversion commands until the touch is removed alert-
ing the AP when the panel is released (by ETAG = 10).
The MAX11800–MAX11803 return to TDM and observe
the start of the next touch event. Panel commands
Figure 10. Edge Interrupt Mode (Direct Conversion Mode)
26
______________________________________________________________________________________
READBACK OPERATIONS ARE NOT SHOWN, BUT ARE EXECUTED DURING TDM PERIODS.
TIRQ DURATION (t
SCAN INTERVAL (t
SCAN DURATION (t
TIRQ
PANEL
IRQ
AP
SD
) IS CONTROLLED BY THE AP AND THE INITIATION OF DM SCAN EVENTS.
) IS SPECIFIED BY THE GENERAL CONFIGURATION REGISTER (0x01).
) IS A FUNCTION OF THE SCAN TYPE AND CONFIGURATION SETTINGS.
TDM
BEGINNING OF TOUCH EVENT
t
IRQ
DCM SCAN
ETAG = 00
2
C/SPI Interface
LPM
t
AP
DCM SCAN
ETAG = 01
issued with CONT = 1 are not capable of fulfilling this
requirement.
The EINT mode provides the least interrupt activity and
the lowest power consumption. Use EINT mode for
general touch-screen applications and applications
requiring high resolution in space and time. When the
TIRQ bus is shared with other functions, poll the gener-
al status register (0x00) to detect the presence of an
interrupt. See Figure 10.
Table 7. Measurement and Event Tags
(Edge Interrupt Mode)
Initial touch (data valid)
Midpress (data valid)
Release/no touch present
(data invalid)
Measurement in progress
(data invalid)
t
SD
MEASUREMENT
EVENT
Z1
Z2
LPM
X
Y
END OF TOUCH EVENT
DCM SCAN
ETAG = 10
MTAG[3:2]
ETAG[1:0]
TDM
00
01
10
11
00
01
10
11