ANPEC APT7844OI-TU, APT7844OI-TR, APT7844NI-TU, APT7844NI-TR Datasheet

Copyright  ANPEC Electronics Corp. Rev. A.6 - Dec., 2001

APT7846

www.anpec.com.tw1

ANPEC reserves the right to make changes to improve reliability or manufacturability without notice, and advise customers to obtain the latest version of relevant information to verify before placing orders.

Touch Screen Controller

Description

The APT7846 is enhance function of APT7843 added battery and temperature monitor function and offer of a bandgap reference voltage for system user. The APT7846 Touch Screen Controller IC provides all the screen driver , A/D converter and control circuits to easily interface to 4 wire resistive touch screen. The IC continually monitors the screen waiting for a touch. When the screen touched , the IC performs A/D converter to determine the location of touch. Also , this device has 1 auxiliary input to A/D converter , allowing for the measurement of other input signal.

Applications

••

• PDAs

••

• Hand held computer

••

• Touch-screen mobile phone

••

• Protable electronic dictionary

••

• Smart IA

Features

••

•

16 Pin SSOP or TSSOP

••

•

Operates With Four Wire Touch Screen

••

•

8-Bit or 12-Bit A/D Converter

••

•

Ratiometric Conversion Eliminates Screen

 Calibration

••

•

1 Auxiliary Analog Input

••

• Full Power Down Control

••

• Internal Bandgap Reference

••

• Serial Interface To Microprocessor

Pin Assignment

Ordering Information

+Vcc 1

14

15

16

8

7

6

5

4

3

2

11

12

13

9

10V

*)6

GND

Y-

X-

Y+

X+

DOUT

BUSY

DIN

DCLK

IN V

4-.

+Vcc

CS

PENIRQ

APT7846

Temp. Range

Package Code

Package Code N : SSOP O : TSSOP Temp. Range I : - 40 to 85 C Handling Code TU : Tube TR : Tape & Reel

°

Handling Code

Copyright  ANPEC Electronics Corp. Rev. A.6 - Dec., 2001

APT7846

www.anpec.com.tw2

Pin Description

Block Diagram

PIN NAME

DESCRIPTION

1+Vcc

Power Supply , 2.7V to 5V.

2X+

Connect to X+ on touch screen.

3Y+

Connect to Y+ on touch screen.

4X-

Connect to X- on touch screen.

5Y-

Connect to Y- on touch screen.

6GND

Ground

7V

*)6

Measure Battery Input.

8IN

Auxiliary input of A/D converter.

9V

4-.

Voltage Reference Input or Output.

10 +Vcc Power Supply , 2.7V to 5V.

11 PENIRQ Pen interrupt. (requires to 100kΩ pull-up resistor externally)

12 DOUT Serial Data Output. This output is high impedance when CS is HIGH.

13 BUSY Busy Output. This output is high impedance whenCS is HIGH.

14 DIN Serial Data input.

15 CS Chip Select. (Active Low)

16 DCLK Serial Clock.

V4-.

IN

V

*)6

Y-

Y+

X+

X-

PENIRQ

DOUT

BUSY

CS

DIN

DCLK

12 Bit or 8 Bit

A/D Converter

Serial

Interface

Screen Driver

MUX

Internal

Reference

Copyright  ANPEC Electronics Corp. Rev. A.6 - Dec., 2001

APT7846

www.anpec.com.tw3

Electrical Characteristics

At TA = -40°C to 85°C, V

CC

= +2.7V , V

REF

= +2.5V , f

SAMPLE

= 125kHz , f

CLK

= 16  f

SAMPLE

= 2MHz , 12-bit mode

, and digital inputs = GND or Vcc , unless otherwise noted.

APT7846

PARAMETER CONDITIONS

MIN TYP MAX

UNIT

DC ACCURACY

Resolution 12 Bits

No missing code 11 Bits

Integral Nonlinearity

±

2 LSB

Offset Error

±

6 LSB

Offset Error Match 0.1 1 LSB

Gain Error

±

4 LSB

Gain Error Match 0.1 1 LSB

Noise 30 uV rms

Power Supply Rejection 70 dB

REFERENCE INPUT

V

REF

Input Voltage Range 1.0 Vcc

DC Leakage Current

±

1

µ

A

V

REF

Input Impedance CS = GND or Vcc 5

G

Ω

V

REF

Input Current 13 40

µ

A

F

SAMPLE

= 12.5 kHz 2.5

µ

A

CS = Vcc 3

µ

A

REFERENCE OUTPUT

Internal Reference Voltage 2.4 2.5 2.6 V

Input Impedence Internal Reference Off 1

G

Ω

DYNAMIC PERFORMANCE

Aperture Delay 30 ns

Aperture Jitter 100 ps

Channel to Channel Isolation VIN = 2.5Vp-p ; FIN = 50kHz 100 dB

CONVERSION RATE

Conversion Time 12 DCLK cycles

Track/Hold Acquisition Time 3 DCLK cycles

Throughput Rate 125 KSPS

SWITCH DRIVERS

On-Resistance

Y+ , X+ 4 15

Ω

Y- , X- 4 15

Ω

Copyright  ANPEC Electronics Corp. Rev. A.6 - Dec., 2001

APT7846

www.anpec.com.tw4

Electrical Characteristics (Cont.)

Note : (1) LSB means least Significant Bit. With V

REF

equal to +2.5V , one LSB is 610µV

APT7846

PARAMETER CONDITIONS

MIN TYP MAX

UNIT

LOGIC INPUTS

Input High Voltage , V

INH

|I

INH

| ≤ +5µA2.4 V

Input Low Voltage , V

INL

|I

INL

| ≤ +5µA0.8V

Input Current , I

IN

±

1

µ

A

Input Capacitance , C

IN

10 pF

LOGIC OUTPUTS

Output High Voltage , V

OH

|IOH| ≤ -250µA

Vcc0. 2

V

Output Low Voltage , V

OL

|IOL| ≤ 250µA0.4V

PENIRQ output low voltage , V

OL

0.2 V

Floating-State Leakage Current

±

10

µ

A

Floating-State Output Capacitance 10 pF

Output Coding Straight ( Natural ) Binary

ANALOG INPUT

Input Voltage Ranges 0 V

REF

V

DC Leakage Current

±

0.1

µ

A

Input Capacitance 30 pF

POWER REQUIREMENTS

Vcc 2.7 3.6 V

Icc Digital I/Ps =0V or Vcc

Normal Mode (Static) Vcc = 3.6V 650

µ

A

Normal Mode (F

SAMPLE

= 12.5kSPS) Vcc = 3.6V 540

µ

A

Shutdown Mode(Static) 3

µ

A

Showdown Vcc = 3.6V 3.6

µ

W

BATTERY MEASURE

Input Voltage Range 0.5 6 V

Input impedance

Sample Battery On 10 K

Ω

Sample Battery Off 1 G

Ω

Accuracy V

REF

-2 2 %

TEMPERATURE RANGE

Normal Operation -40 85

°

C

Copyright  ANPEC Electronics Corp. Rev. A.6 - Dec., 2001

APT7846

www.anpec.com.tw5

FIGURE 1. Basic Operation of the APT7846

Chip Overview

The APT7846 is a successive approximation analog-to-digital (A/D) converter based around a capacitive redistribution DAC. Figure 1 show basic operation of the APT7846. The APT7846 communicates via a 4-wire serial interface. The device requires an external reference voltage Vref. The value of the reference voltage directly sets the input range of the converter. Otherwise you can use internal reference Voltage to do conversion.

The APT7846 primary function is to control resistive touchscreens. When a touch is detected , pen interrupt pin will go low to wake up extenal microprocessor . The microprocessor writes register to initiate

Analog Input

The analog input to the converter is provided via a four-channel multiplexer. Figure 2 shows a simplified diagram of the APT7846 with the difference input of the A/D converter , and the converters reference. Table I and Table II also show the relationship between the A2 , A1 , A0 , SER/ and the configuration of the APT7846. See the section of single-ended reference mode and differential reference mode for more details.

,.4

conversion. This A/D converter may also be used to measure voltage presented on the IN Pin or to measure battery presented on the V

BAT

Pin.

1

14

15

16

8

7

6

5

4

3

2

11

12

13

9

10

V

BAT

GND

Y-

X-

Y+

X+

DOUT

BUSY

DIN

DCLK

IN V

REF

+Vcc

CS

PENIRQ

+Vcc

APT7846

100k ohm (optional)

Auxiliary Input

+2.7V to +5v

To Touch Screen

1uF

to

10uF

(Optional)

0.1uF

Connect to Microprossor

Battery Input