Datasheet

ManualsBrandsTEXAS INSTRUMENTS ManualsData collecting ICsData acquisition IC - Touchscreen controller 12 Bit 1x TSC input SSOP 16

FEATURES

● SAME PINOUT AS ADS7843

● 2.2V TO 5.25V OPERATION

● INTERNAL 2.5V REFERENCE

● DIRECT BATTERY MEASUREMENT (0V to 6V)

● ON-CHIP TEMPERATURE MEASUREMENT

● TOUCH-PRESSURE MEASUREMENT

● QSPI

/SPI

3-WIRE INTERFACE

● AUTO POWER-DOWN

● TSSOP-16, SSOP-16, QFN-16,

AND VFBGA-48 PACKAGES

APPLICATIONS

● PERSONAL DIGITAL ASSISTANTS

● PORTABLE INSTRUMENTS

● POINT-OF-SALE TERMINALS

● PAGERS

● TOUCH SCREEN MONITORS

● CELLULAR PHONES

TOUCH SCREEN CONTROLLER

DESCRIPTION

The ADS7846 is a next-generation version to the industry

standard ADS7843 4-wire touch screen controller. The

ADS7846 is 100% pin-compatible with the existing ADS7843,

and drops into the same socket. This allows for easy upgrade

of current applications to the new version. Only software

changes are required to take advantage of the added fea-

tures of direct battery measurement, temperature measure-

ment, and touch-pressure measurement. The ADS7846 also

has an on-chip 2.5V reference that can be used for the

auxiliary input, battery monitor, and temperature measure-

ment modes. The reference can also be powered down when

not used to conserve power. The internal reference operates

down to 2.7V supply voltage while monitoring the battery

voltage from 0V to 6V.

The low-power consumption of < 0.75mW (typ at 2.7V,

reference off), high speed (up to 125kHz clock rate), and on-

chip drivers make the ADS7846 an ideal choice for battery-

operated systems such as personal digital assistants (PDAs)

with resistive touch screens, pagers, cellular phones, and

other portable equipment. The ADS7846 is available in the

small TSSOP-16, SSOP-16, QFN-16, and VFBGA-48 pack-

ages and is specified over the –40°C to +85°C temperature

range.

CDAC

Internal 2.5V

Reference

SAR

ADS7846

Comparator

6-Channel

MUX

Serial

Data

Out

Temperature

Sensor

Battery

Monitor

DOUT

BUSY

DCLK

DIN

BAT

AUX

REF

X+

X–

Y+

Y–

PENIRQ

ADS7846

SBAS125H – SEPTEMBER 1999 – REVISED JANUARY 2005

www.ti.com

PRODUCTION DATA information is current as of publication date.

Products conform to specifications per the terms of Texas Instruments

standard warranty. Production processing does not necessarily include

testing of all parameters.

US Patent No. 6246394

QSPI and SPI are registered trademarks of Motorola.

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of

Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

All trademarks are the property of their respective owners.

Summary of content (30 pages)

PAGE 1
ADS7846 ADS 7846 AD S784 6 ® AD S784 6 SBAS125H – SEPTEMBER 1999 – REVISED JANUARY 2005 TOUCH SCREEN CONTROLLER FEATURES DESCRIPTION ● SAME PINOUT AS ADS7843 The ADS7846 is a next-generation version to the industry standard ADS7843 4-wire touch screen controller. The ADS7846 is 100% pin-compatible with the existing ADS7843, and drops into the same socket. This allows for easy upgrade of current applications to the new version.
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ABSOLUTE MAXIMUM RATINGS(1) +VCC to GND ........................................................................ –0.3V to +6V Analog Inputs to GND ............................................ –0.3V to +VCC + 0.3V Digital Inputs to GND ............................................. –0.3V to +VCC + 0.3V Power Dissipation .......................................................................... 250mW Maximum Junction Temperature ...................................................
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ELECTRICAL CHARACTERISTICS At TA = –40°C to +85°C, +VCC = +2.7V, VREF = 2.5V internal voltage, fSAMPLE = 125kHz, fCLK = 16 • fSAMPLE = 2MHz, 12-bit mode, and digital inputs = GND or +VCC, unless otherwise noted. ADS7846E PARAMETER ANALOG INPUT Full-Scale Input Span Absolute Input Range CONDITIONS MIN Positive Input-Negative Input Positive Input Negative Input 0 –0.2 –0.
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PIN CONFIGURATION Top View Top View SSOP, TSSOP VFBGA CS DCLK +VCC 1 16 DCLK X+ 2 15 CS Y+ 3 14 DIN X– 4 13 BUSY Y– 5 GND 6 ADS7846 1 2 DIN 3 BUSY DOUT 4 5 6 A NC 7 NC B NC C NC NC NC NC NC NC NC NC PENIRQ +VCC 12 DOUT 11 PENIRQ +VCC +VCC D NC NC NC NC NC E NC NC NC NC NC F NC NC NC NC NC NC X+ VBAT 7 10 +VCC AUX 8 9 VREF VREF AUX Y+ G NC NC X– Y– GND GND VBAT BUSY 1 DIN 2 13 VREF 14 +VCC 15 PENIRQ QFN 16 DOUT
PAGE 5
TYPICAL CHARACTERISTICS At TA = +25°C, +VCC = +2.7V, VREF = External +2.5V, fSAMPLE = 125kHz, and fCLK = 16 • fSAMPLE = 2MHz, unless otherwise noted.
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TYPICAL CHARACTERISTICS (Cont.) At TA = +25°C, +VCC = +2.7V, VREF = External +2.5V, fSAMPLE = 125kHz, and fCLK = 16 • fSAMPLE = 2MHz, unless otherwise noted.
PAGE 7
TYPICAL CHARACTERISTICS (Cont.) At TA = +25°C, +VCC = +2.7V, VREF = External +2.5V, fSAMPLE = 125kHz, and fCLK = 16 • fSAMPLE = 2MHz, unless otherwise noted. INTERNAL VREF vs TURN-ON TIME 2.4860 80 Internal VREF (%) 100 2.4855 2.4850 3.6 3.5 3.4 3.3 3.2 3.1 3.0 2.9 2.8 0 2.7 2.4840 0 200 400 600 800 1000 1200 Turn-On Time (µS) VCC (V) TEMP DIODE VOLTAGE vs TEMPERATURE (2.
PAGE 8
THEORY OF OPERATION possible to negate the error from each touch panel driver switch’s on-resistance (if this is a source of error for the particular measurement). The ADS7846 is a classic successive approximation register (SAR) analog-to-digital converter (ADC). The architecture is based on capacitive redistribution which inherently includes a sample-and-hold function. The converter is fabricated on a 0.6µm CMOS process.
PAGE 9
+VCC PENIRQ TEMP1 VREF TEMP0 A2-A0 (Shown 001B) SER/DFR (Shown High) X+ X– Ref On/Off Y+ +IN Y– +REF Converter 2.5V Reference –IN –REF 7.5kΩ VBAT 2.5kΩ AUX Battery On GND FIGURE 2. Simplified Diagram of Analog Input. INTERNAL REFERENCE Reference Power Down The ADS7846 has an internal 2.5V voltage reference that can be turned on or off with the control bit, PD1 = 1 (see Table V and Figure 3).
PAGE 10
voltage, more care must be taken to provide a clean layout including adequate bypassing, a clean (low-noise, low-ripple) power supply, a low-noise reference (if an external reference is used), and a low-noise input signal. +VCC The voltage into the VREF input directly drives the capacitor digital-to-analog converter (CDAC) portion of the ADS7846. Therefore, the input current is very low (typically < 13µA).
PAGE 11
required for X-position, Y-position, and Z-position measurements. Option 3 is to operate in the 15 Clock-per-Conversion mode which overlaps the analog-to-digital conversions and maintains the touch screen drivers on until commanded to stop by the processor (see Figure 12). TEMPERATURE MEASUREMENT In some applications, such as battery recharging, a measurement of ambient temperature is required.
PAGE 12
PRESSURE MEASUREMENT Measure X-Position Measuring touch pressure can also be done with the ADS7846. To determine pen or finger touch, the pressure of the touch needs to be determined. Generally, it is not necessary to have very high performance for this test; therefore, the 8-bit resolution mode is recommended (however, calculations will be shown here are in 12-bit resolution mode). There are several different ways of performing this measurement. The ADS7846 supports two methods.
PAGE 13
sample-and-hold goes into the hold mode and the touch panel drivers turn off (in single-ended mode). The next 12 clock cycles accomplish the actual analog-to-digital conversion. If the conversion is ratiometric (SER/DFR = 0), the drivers are on during the conversion and a 13th clock cycle is needed for the last bit of the conversion result. Three more clock cycles are needed to complete the last byte (DOUT will be low), which are ignored by the converter.
PAGE 14
16 Clocks-per-Conversion SYMBOL DESCRIPTION MIN The control bits for conversion n + 1 can be overlapped with conversion n to allow for a conversion every 16 clock cycles, as shown in Figure 10. This figure also shows possible serial communication occurring with other serial peripherals between each byte transfer from the processor to the converter. This is possible provided that each conversion completes within 1.6ms of starting.
PAGE 15
Clocks-per-Conversion 8-Bit Conversion Figure 12 provides the fastest way to clock the ADS7846. This method does not work with the serial interface of most microcontrollers and digital signal processors, as they are generally not capable of providing 15 clock cycles per serial transfer. However, this method can be used with field programmable gate arrays (FPGAs) or application specific integrated circuits (ASICs).
PAGE 16
Figure 14 shows the difference between reducing the DCLK frequency (scaling DCLK to match the conversion rate) or maintaining DCLK at the highest frequency and reducing the number of conversions per second. In the latter case, the converter spends an increasing percentage of time in powerdown mode (assuming the auto power-down mode is active). 1000 Supply Current (µA) fCLK = 16 • fSAMPLE 100 fCLK = 2MHz 10 TA = 25°C +VCC = +2.7V 1 1k 10k 100k 1M fSAMPLE (Hz) FIGURE 14.
PAGE 17
The GND pin must be connected to a clean ground point. In many cases, this is the analog ground. Avoid connections which are too near the grounding point of a microcontroller or digital signal processor. If needed, run a ground trace directly from the converter to the power-supply entry or batteryconnection point. The ideal layout includes an analog ground plane dedicated to the converter and associated analog circuitry.
PAGE 18
PACKAGE OPTION ADDENDUM www.ti.
PAGE 19
PACKAGE OPTION ADDENDUM www.ti.com 11-Apr-2013 (2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability information and additional product content details. TBD: The Pb-Free/Green conversion plan has not been defined.
PAGE 20
PACKAGE MATERIALS INFORMATION www.ti.com 24-Apr-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant ADS7846E/2K5 SSOP DBQ 16 2500 330.0 12.4 6.4 5.2 2.1 8.0 12.0 Q1 ADS7846IRGVR VQFN RGV 16 2500 330.0 12.4 4.3 4.3 1.5 8.0 12.0 Q2 ADS7846IRGVT VQFN RGV 16 250 180.0 12.4 4.3 4.3 1.5 8.0 12.
PAGE 21
PACKAGE MATERIALS INFORMATION www.ti.com 24-Apr-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) ADS7846E/2K5 SSOP DBQ 16 2500 367.0 367.0 35.0 ADS7846IRGVR VQFN RGV 16 2500 338.1 338.1 20.6 ADS7846IRGVT VQFN RGV 16 250 210.0 185.0 35.
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MECHANICAL DATA MPLG008D – APRIL 2000 – REVISED FEBRUARY 2002 GQC (S-PBGA-N48) PLASTIC BALL GRID ARRAY 4,10 3,90 SQ 3,00 TYP 0,50 G F 0,50 E D 3,00 TYP C B A 1 A1 Corner 2 3 4 5 6 7 Bottom View 0,77 0,71 1,00 MAX Seating Plane 0,35 0,25 0,25 0,05 M 0,08 0,15 4200460/E 01/02 NOTES: A. B. C. D. All linear dimensions are in millimeters. This drawing is subject to change without notice.
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