MAX11800_1010 Datasheet, PDF(26/59 Page) Maxim Integrated Products – Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface

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MAX11800_1010 Datasheet, PDF (26/59 Pages) Maxim Integrated Products – Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface

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Low-Power, Ultra-Small Resistive Touch-Screen

Controllers with I2C/SPI Interface

PANEL

TOUCH

TIRQ

BEGINNING OF TOUCH EVENT

INITIATED AND CONTROLLED BY

THE AP

END OF TOUCH EVENT

TDM

DCM SCAN

ETAG = 00

tAP

tSD

READBACK OPERATIONS ARE NOT SHOWN, BUT ARE EXECUTED DURING TDM PERIODS.

SCAN INTERVAL (tAP) IS CONTROLLED BY THE AP AND THE INITIATION OF DM SCAN EVENTS.

SCAN DURATION (tSD) IS A FUNCTION OF THE SCAN TYPE AND CONFIGURATION SETTINGS.

DCM = DIRECT CONVERSION MODE

Figure 9. Continuous Interrupt Mode (Direct Conversion Mode)

Procedure: The EINT mode reduces TIRQ activity.

During EINT, the MAX11800âMAX11803 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 present 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

MAX11800âMAX11803 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 MAX11800âMAX11803 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 MAX11800âMAX11803 return to TDM and observe

the start of the next touch event. Panel commands

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)

MEASUREMENT

MTAG[3:2]

EVENT

Initial touch (data valid)

Midpress (data valid)

Release/no touch present

(data invalid)

Measurement in progress

(data invalid)

ETAG[1:0]

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