TSC2046E datasheet(16/34 Pages) TI2

16 / 34 page

TSC2046E

SBAS417B − JUNE 2007 − REVISED JANUARY 2008

www.ti.com

X-Position,

Y-Position,

and

Pressure-Touch

are

measured in the single-ended mode, an external reference

voltage is needed. The TSC2046E must also be powered

from the external reference. Caution should be observed

when using the single-ended mode such that the input

voltage to the ADC does not exceed the internal reference

voltage, especially if the supply voltage is greater than

2.7V.

NOTE: The differential mode can only be used for

X-Position,

Y-Position,

and

Pressure-Touch

measurements. All other measurements require the

single-ended mode.

PD0 and PD1—Table 5 describes the power-down and

the internal reference voltage configurations. The internal

reference voltage can be turned on or off independently of

the ADC. This feature can allow extra time for the internal

reference voltage to settle to the final value prior to making

a conversion. Make sure to also allow this extra wake-up

time if the internal reference is powered down. The ADC

requires no wake-up time and can be instantaneously

used. Also note that the status of the internal reference

power-down is latched into the part (internally) with BUSY

going high. In order to turn the reference off, an additional

write to the TSC2046E is required after the channel has

been converted.

PD1

PD0

PENIRQ

DESCRIPTION

Enabled

Power-Down Between Conversions. When

each conversion is finished, the converter

enters a low-power mode. At the start of the

next conversion, the device instantly powers up

to full power. There is no need for additional

delays to ensure full operation, and the very first

conversion is valid. The Y− switch is on when in

power-down.

Disabled

Reference is off and ADC is on.

Enabled

Reference is on and ADC is off.

Disabled

Device is always powered. Reference is on and

ADC is on.

Table 5. Power-Down and Internal Reference

Selection

PENIRQ OUTPUT

The pen-interrupt output function is shown in Figure 10.

While in power-down mode with PD0 = 0, the Y-driver is on

and connects the Y-plane of the touch screen to GND. The

PENIRQ output is connected to the X+ input through two

transmission gates. When the screen is touched, the X+

input is pulled to ground through the touch screen.

In most of the TSC2046E models, the internal pullup resistor

value is nominally 50k

Ω, but this value may vary between

36k

Ω and 67kΩ given process and temperature variations.

In order to assure a logic low of 0.35

S (+VCC) is presented

to the PENIRQ circuitry, the total resistance between the X+

and Y− terminals must be less than 21k

Ω.

PENIRQ

50k

Ω

90k

Ω

Y+ or X+ drivers on,

or TEMP0, TEMP1

measurements activated.

Y+

X+

−

TEMP0

TEMP1

TEMP

DIODE

High except

when TEMP0,

TEMP1 activated.

Level

Shifter

IOVDD

Figure 10. PENIRQ Functional Block Diagram

The −90 version of the TSC2046E uses a nominal 90k

Ω

pullup resistor that allows the total resistance between the

X+ and Y− terminals to be as high as 30k

Ω. Note that the

higher pullup resistance causes a slower response time of

the PENIRQ to a screen touch, so user software should

take this into account.

The PENIRQ output goes low due to the current path through

the touch screen to ground, initiating an interrupt to the

processor. During the measurement cycle for X-, Y-, and

Z-Position, the X+ input is disconnected from the PENIRQ

internal pull-up resistor. This disconnection is done to

eliminate any leakage current from the internal pull-up

resistor through the touch screen, thus causing no errors.

Furthermore, the PENIRQ output is disabled and low during

the measurement cycle for X-, Y-, and Z-Position. The

PENIRQ

output

disabled

and

high

during

the

measurement cycle for battery monitor, auxiliary input, and

chip temperature. If the last control byte written to the

TSC2046E contains PD0 = 1, the pen-interrupt output

function is disabled and is not able to detect when the screen

is touched. In order to re-enable the pen-interrupt output

function under these circumstances, a control byte needs to

be written to the TSC2046E with PD0 = 0. If the last control

byte written to the TSC2046E contains PD0 = 0, the

pen-interrupt output function is enabled at the end of the

conversion. The end of the conversion occurs on the falling

edge of DCLK after bit 1 of the converted data is clocked out

of the TSC2046E.

It is recommended that the processor mask the interrupt that

PENIRQ is associated with whenever the processor sends

a control byte to the TSC2046E. This masking prevents false

triggering of interrupts when the PENIRQ output is disabled

in the cases discussed in this section.

TSC2046E Datasheet(PDF) 16 Page - Texas Instruments

TSC2046E Datasheet(HTML) 16 Page - Texas Instruments

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34

Datasheet Download

Link URL