MAX1233EGI ,15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad ControllerApplications Automatic Detection of Screen Touch, Key Press,Personal Digital Assistantsand End of ..
MAX1236EUA ,2.7V to 3.6V and 4.5V to 5.5V, Low-Power, 4-/12-Channel, 2-Wire Serial, 12-Bit ADCsMAX1236–MAX123919-2333; Rev 2; 2/032.7V to 3.6V and 4.5V to 5.5V, Low-Power,4-/12-Channel, 2-Wire S ..
MAX1236EUA+ ,2.7V to 3.6V and 4.5V to 5.5V, Low-Power, 4-/12-Channel, 2-Wire Serial, 12-Bit ADCsFeaturesThe MAX1236–MAX1239 low-power, 12-bit, multichan- 2♦ High-Speed I C-Compatible Serial Inter ..
MAX1236EUA+T ,2.7V to 3.6V and 4.5V to 5.5V, Low-Power, 4-/12-Channel, 2-Wire Serial, 12-Bit ADCsELECTRICAL CHARACTERISTICS(V = 2.7V to 3.6V (MAX1237/MAX1239), V = 4.5V to 5.5V (MAX1236/MAX1238), ..
MAX1237EUA ,2.7V to 3.6V and 4.5V to 5.5V, Low-Power, 4-/12-Channel, 2-Wire Serial, 12-Bit ADCsApplicationsMedical Instruments Ordering InformationBattery-Powered Test Equipment2TEMP PIN- I C SL ..
MAX1237EUA+T ,2.7V to 3.6V and 4.5V to 5.5V, Low-Power, 4-/12-Channel, 2-Wire Serial, 12-Bit ADCsMAX1236–MAX123919-2333; Rev 7; 5/102.7V to 3.6V and 4.5V to 5.5V, Low-Power,4-/12-Channel, 2-Wire S ..
MAX361ESE ,Precision, Quad, SPST Analog SwitchesApplicationsMAX362CPE 0°C to +70°C 16 Plastic DIPSample-and-Hold CircuitsMAX362CSE 0°C to +70°C 16 ..
MAX361ESE+ ,Precision, Quad, SPST Analog SwitchesApplicationsMAX361MJE -55°C to +125°C 16 CERDIPSample-and-Hold CircuitsMAX362CPE 0°C to +70°C 16 Pl ..
MAX361MJE ,Precision, Quad, SPST Analog SwitchesFeatures' Low On Resistance: < 45Ω Typical (85Ω Max)The MAX361/MAX362 are precision, quad, single-p ..
MAX3624UTJ , Low-Jitter, Precision Clock Generator with Four Outputs
MAX362CPE ,Precision, Quad, SPST Analog SwitchesELECTRICAL CHARACTERISTICS—Dual Supplies(V+ = 15V, V- = -15V, GND = 0V, V = 2.4V, V = 0.8V, T = T t ..
MAX362CPE+ ,Precision, Quad, SPST Analog SwitchesFeatures♦ Low On Resistance: < 45Ω Typical (85Ω Max)The MAX361/MAX362 are precision, quad, single-p ..
MAX1233EGI
15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller
General DescriptionThe MAX1233/MAX1234 are complete PDA controllers in
a 5mm ×5mm, 28-pin QFN package. They feature a
12-bit analog-to-digital converter (ADC), low on-resis-
tance switches for driving resistive touch screens, an
internal +1.0V/+2.5V or external reference, ±2°C accu-
rate, on-chip temperature sensor, direct +6V battery mon-
itor, keypad controller, 8-bit digital-to-analog converter
(DAC), and a synchronous serial interface. Each of the
keypad controllers’ eight row and column inputs can be
reconfigured as general-purpose parallel I/O pins (GPIO).
All analog inputs are fully ESD protected, eliminating the
need for external TransZorb™ devices.
The MAX1233/MAX1234 offer programmable resolution
and sampling rates. Interrupts from the devices alert the
host processor when data is ready, when the screen is
touched, or a key press is detected. Software-
configurable scan control and internal timers give the user
flexibility without burdening the host processor. These
devices consume only 260µA at the maximum sampling
rate of 50ksps. Supply current falls to below 50µA for
sampling rates of 10ksps. The MAX1233/MAX1234 are
guaranteed over the -40°C to +85°C temperature range.
ApplicationsPersonal Digital Assistants
Pagers
Touch-Screen Monitors
Cellular Phones
MP3 Players
Portable Instruments
Point-of-Sale Terminals
FeaturesESD-Protected Analog Inputs±15kV IEC 1000-4-2 Air-Gap Discharge
±8kV IEC 1000-4-2 Contact Discharge
Single-Supply Operation
+2.7V to +3.6V (MAX1233)
+4.75V to +5.25V (MAX1234)4-Wire Touch-Screen InterfaceInternal +1.0V/+2.5V Reference or External
Reference (+1.0V to AVDD)SPI™/QSPI™/MICROWIRE™-Compatible 10MHz
Serial Interface12-Bit, 50ksps ADC Measures
Resistive Touch-Screen Position and Pressure
Two Auxiliary Analog Inputs
Two Battery Voltages (0.5V to 6V)
On-Chip Temperature8-Bit DAC for LCD Bias Control4 ×4 Keypad Programmable Controller Offers Up
to Eight GPIO PinsAutomatic Detection of Screen Touch, Key Press,
and End of ConversionProgrammable 8-, 10-, 12-Bit ResolutionProgrammable Conversion RatesAutoShutdown™Between ConversionsLow Power
260µA at 50ksps
50µA at 10ksps
6µA at 1ksps
0.3µA Shutdown Current28-Pin 5mm ×5mm QFN Package
MAX1233/MAX1234ouch-Screen
Controllers Include DAC and Keypad Controller
Pin Configuration
Ordering InformationTransZorb is a trademark of General Semiconductor Industries,
Inc.
SPI and QSPI are trademarks of Motorola, Inc.
MICROWIRE is a trademark of National Semiconductor Corp.
AutoShutdown is a trademark of Maxim Integrated Products, Inc.
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(DVDD= AVDD= +2.7V to +3.6V (MAX1233), DVDD= AVDD= +4.75V to +5.25V (MAX1234), external reference VREF= 2.5V
(MAX1233), VREF= 4.096V (MAX1234); fSCLK= 10MHz, fSAMPLE= 50ksps, 12-bit mode, 0.1µF capacitor at REF, TA= -40°C to
+85°C, unless otherwise noted. Typical values are at TA= +25°C.)
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
AVDDto GND............................................................-0.3V to +6V
DVDDto AVDD.......................................................-0.3V to +0.3V
Digital Inputs/Outputs to GND.................-0.3V to (DVDD + 0.3V)
X+, Y+, X-, Y-, AUX1, AUX2,
and REF to GND..................................-0.3V to (AVDD + 0.3V)
BAT1, BAT2 to GND.................................................-0.3V to +6V
Maximum ESD per IEC 1000-4-2 (per MIL STD-883 HBM)
X+, X-, Y+, Y-, AUX1, AUX2, BAT1, BAT2......................±15kV
All Other Pins.....................................................................±2.5kV
Maximum Current into Any Pin............................................50mA
Continuous Power Dissipation (TA= +70°C)
28-Pin QFN (derate 28.5mW/°C above +70°C).................2W
Operating Temperature Range...........................-40°C to +85°C
Storage Temperature Range.............................-60°C to +150°C
Lead Temperature (soldering, 10s).................................+300°C
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
ELECTRICAL CHARACTERISTICS (continued)(DVDD= AVDD= +2.7V to +3.6V (MAX1233), DVDD= AVDD= +4.75V to +5.25V (MAX1234), external reference VREF= 2.5V
(MAX1233), VREF= 4.096V (MAX1234); fSCLK= 10MHz, fSAMPLE= 50ksps, 12-bit mode, 0.1µF capacitor at REF, TA= -40°C to
+85°C, unless otherwise noted. Typical values are at TA= +25°C.)
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
ELECTRICAL CHARACTERISTICS (continued)(DVDD= AVDD= +2.7V to +3.6V (MAX1233), DVDD= AVDD= +4.75V to +5.25V (MAX1234), external reference VREF= 2.5V
(MAX1233), VREF= 4.096V (MAX1234); fSCLK= 10MHz, fSAMPLE= 50ksps, 12-bit mode, 0.1µF capacitor at REF, TA= -40°C to
+85°C, unless otherwise noted. Typical values are at TA= +25°C.)
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
ELECTRICAL CHARACTERISTICS (continued)(DVDD= AVDD= +2.7V to +3.6V (MAX1233), DVDD= AVDD= +4.75V to +5.25V (MAX1234), external reference VREF= 2.5V
(MAX1233), VREF= 4.096V (MAX1234); fSCLK= 10MHz, fSAMPLE= 50ksps, 12-bit mode, 0.1µF capacitor at REF, TA= -40°C to
+85°C, unless otherwise noted. Typical values are at TA= +25°C.)
Note 2:Relative accuracy is the deviation of the analog value at any code from its theoretical value after the offset and gain errors
have been removed.
Note 3:Offset nulled.
Note 4:Difference between TEMP1 and TEMP2; temperature in °K = (VTEMP2- VTEMP1) ×2680°K/V. No calibration is necessary.
Note 5:Temperature coefficient is -2.1mV/°C. Determine absolute temperature by extrapolating from a calibrated value.
Note 6:ADC performance is limited by the conversion noise floor, typically 300µVP-P. An external reference below 2.5V can
compromise the ADC performance.
Note 7:Guaranteed from code 5 to 255.
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
ELECTRICAL CHARACTERISTICS (continued)(DVDD= AVDD= +2.7V to +3.6V (MAX1233), DVDD= AVDD= +4.75V to +5.25V (MAX1234), external reference VREF= 2.5V
(MAX1233), VREF= 4.096V (MAX1234); fSCLK= 10MHz, fSAMPLE= 50ksps, 12-bit mode, 0.1µF capacitor at REF, TA= -40°C to
+85°C, unless otherwise noted. Typical values are at TA= +25°C.)
Note 8:The offset value extrapolated from the range over which the INL is guaranteed.
Note 9:Output settling time is measured by stepping from code 5 to 255, and from code 255 to 5.
Note 10:Actual output voltage at full scale is 255/256 ×VREFDAC.
Note 11:Resistance is open when configured as GPIO or in shutdown.
Note 12:AVDDand DVDDshould not differ by more than 300mV.
Note 13:When configured as GPIO.
Timing Diagram
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
SHUTDOWN CURRENT
vs. ANALOG SUPPLY VOLTAGEMAX1233/34 toc01
AVDD (V)
SHUTDOWN CURRENT (nA)
SHUTDOWN CURRENT
vs. TEMPERATURE
MAX1233/34 toc02
TEMPERATURE (°C)
SHUTDOWN CURRENT (nA)6040200-20
INTERNAL OSCILLATOR FREQUENCY
vs. ANALOG SUPPLY VOLTAGE
MAX1233/34 toc03
AVDD (V)
INTERNAL OSCILLATOR FREQUENCY (MHz)
INTERNAL OSCILLATOR FREQUENCY
vs. TEMPERATURE
MAX1233/34 toc04
TEMPERATURE (°C)
INTERNAL OSCILLATOR FREQUENCY (MHz)6040200-20
TEMP1 DIODE VOLTAGE
vs. ANALOG SUPPLY VOLTAGE
MAX1233/34 toc05
AVDD (V)
TEMP1 DIODE VOLTAGE (V)
TEMP1 DIODE VOLTAGE
vs. TEMPERATURE
MAX1233/34 toc06
TEMPERATURE (°C)
TEMP1 DIODE VOLTAGE (V)65-25-105352050
TEMP2 DIODE VOLTAGE
vs. ANALOG SUPPLY VOLTAGE
MAX1233/34 toc07
AVDD (V)
TEMP2 DIODE VOLTAGE (V)
TEMP2 DIODE VOLTAGE
vs. TEMPERATURE
MAX1233/34 toc08
TEMPERATURE (°C)
TEMP2 DIODE VOLTAGE (V)655035205-10-25
Typical Operating Characteristics
(AVDD = DVDD= 3V (MAX1233) or 5V (MAX1234), external VREF= +2.5V (MAX1233), external VREF= +4.096V (MAX1234), fSCLK=
10MHz (50% duty cycle), fSAMPLE= 20ksps, CLOAD= 50pF, 0.1µF capacitor at REF, TA= +25°C, unless otherwise noted.)
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
Typical Operating Characteristics (continued)(AVDD = DVDD= 3V (MAX1233) or 5V (MAX1234), external VREF= +2.5V (MAX1233), external VREF= +4.096V (MAX1234), fSCLK=
10MHz (50% duty cycle), fSAMPLE= 20ksps, CLOAD= 50pF, 0.1µF capacitor at REF, TA= +25°C, unless otherwise noted.)
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad ControllerDAC INTEGRAL NONLINEARITY vs. CODE
MAX1233/34 toc19
CODE
INL (LSB)150250
DAC DIFFERENTIAL NONLINEARITY
vs. OUTPUT CODEMAX1233/34 toc20
OUTPUT CODE
DNL (LSB)
Typical Operating Characteristics (continued)
(AVDD = DVDD= 3V (MAX1233) or 5V (MAX1234), external VREF= +2.5V (MAX1233), external VREF= +4.096V (MAX1234), fSCLK=
10MHz (50% duty cycle), fSAMPLE= 20ksps, CLOAD= 50pF, 0.1µF capacitor at REF, TA= +25°C, unless otherwise noted.)
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
ADC REFERENCE VOLTAGE
vs. ANALOG SUPPLY VOLTAGEMAX1233/34 toc25
AVDD (V)
REF
(V)
REF
(V)
ADC REFERENCE VOLTAGE
vs. TEMPERATURE
TEMPERATURE (°C)
REF
(V)
REF
(V)
MAX1233/34 toc2660-2002040-40
DAC FULL-SCALE ERROR
vs. ANALOG SUPPLY VOLTAGE
MAX1233/34 toc21
AVDD (V)
FULL-SCALE ERROR (LSB)
FULL-SCALE ERROR (%)
DAC FULL-SCALE ERROR
vs. TEMPERATURE
MAX1233/34 toc22
TEMPERATURE (°C)
FULL-SCALE ERROR (LSB)
FULL-SCALE ERROR (%)
DAC SUPPLY CURRENT
vs. ANALOG SUPPLY VOLTAGEMAX1233/34 toc23
AVDD (V)
DAC SUPPLY CURRENT (
MAX1233/34 toc24
TEMPERATURE (°C)
DAC SUPPLY CURRENT (60-2002040
DAC SUPPLY CURRENT
vs. TEMPERATURE
Typical Operating Characteristics (continued)
(AVDD = DVDD= 3V (MAX1233) or 5V (MAX1234), external VREF= +2.5V (MAX1233), external VREF= +4.096V (MAX1234), fSCLK=
10MHz (50% duty cycle), fSAMPLE= 20ksps, CLOAD= 50pF, 0.1µF capacitor at REF, TA= +25°C, unless otherwise noted.)
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
Typical Operating Characteristics (continued)(AVDD = DVDD= 3V (MAX1233) or 5V (MAX1234), external VREF= +2.5V (MAX1233), external VREF= +4.096V (MAX1234), fSCLK=
10MHz (50% duty cycle), fSAMPLE= 20ksps, CLOAD= 50pF, 0.1µF capacitor at REF, TA= +25°C, unless otherwise noted.)
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
Detailed DescriptionThe MAX1233/MAX1234 are 4-wire touch-screen con-
trollers. Figure1shows the functional diagram of the
MAX1233/MAX1234. Each device includes a 12-bit sam-
pling ADC, 8-bit voltage output DAC, keypad scanner
that can also be configured as a GPIO, internal clock,
reference, temperature sensor, two battery monitor
inputs, two auxiliary analog inputs, SPI/QSPI/
MICROWIRE-compatible serial interface, and low on-
resistance switches for driving touch screens.
The 16-bit register inside the MAX1233/MAX1234
allows for easy control and stores results that can be
read at any time. The BUSYoutput indicates that a
functional operation is in progress. The PENIRQand
KEYIRQoutputs, respectively, indicate that a screen
touch or a key press has occurred.
Touch-Screen OperationThe 4-wire touch-screen controller works by creating a
voltage gradient across the vertical or horizontal resis-
tive touch screen connected to the analog inputs of the
MAX1233/MAX1234, as shown in Figure2. The voltage
across the touch-screen panels is applied through inter-
nal MOSFET switches that connect each resistive layer
to AVDDand ground. For example, to measure the Y
position when a pointing device presses on the touch
screen, the Y+ and Y- drivers are turned on, connecting
one side of the vertical resistive layer to AVDDand the
other side to ground. The horizontal resistive layer func-
tions as a sense line. One side of this resistive layer gets
connected to the X+ input, while the other side is left
open or floating. The point where the touch screen is
pressed brings the two resistive layers in contact and
creates a voltage-divider at that point. The data convert-
er senses the voltage at the point of contact through the
X+ input and digitizes it.
12-Bit ADC
Analog InputsFigure3shows a block diagram of the ADC’s analog
input section including the input multiplexer, the differen-
tial input, and the differential reference. The input multi-
plexer switches between X+, X-, Y+, Y-, AUX1, AUX2,
BAT1, BAT2, and the internal temperature sensor.
The time required for the T/H to acquire an input signal
is a function of how quickly its input capacitance is
charged. If the input signal’s source impedance is high,
the acquisition time lengthens, and more time must be
allowed. The acquisition time (tACQ) is the maximum
time the device takes to acquire the input signal to 12-
bit accuracy. Configure tACQby writing to the ADC
control register. See Table1for the maximum input sig-
nal source impedance (RSOURCE) for complete settling
during acquisition.
Accommodate higher source impedances by placing a
0.1µF capacitor between the analog input and GND.
Input BandwidthThe ADC’s input-tracking circuitry has a 0.5MHz small-
signal bandwidth. To avoid high-frequency signals
being aliased into the frequency band of interest, anti-
alias filtering is recommended.
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
Analog Input ProtectionInternal protection diodes that clamp the analog input
to AVDDand GND allow the analog input pins to swing
from GND - 0.3V to AVDD+ 0.3V without damage.
Analog inputs must not exceed AVDD by more than
50mV or be lower than GND by more than 50mV for
accurate conversions. If an off-channel analog input
voltage exceeds the supplies, limit the input current to
50mA. All analog inputs are also fully ESD protected
to ±8kV, using the Contact-Discharge method and
±15kV using the Air-Gap method specified in IEC-
Reference for ADC
Internal ReferenceThe MAX1233/MAX1234 offer an internal voltage refer-
ence for the ADC that can be set to +1.0V or +2.5V. The
MAX1233/MAX1234 typically use the internal reference
for battery monitoring, temperature measurement, and for
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controllermeasurement of the auxiliary inputs. Figure4shows the
on-chip reference circuitry of the MAX1233/MAX1234.
Set the internal reference voltage by writing to the RFV
bits in the ADC control register (see Tables4, 5, and 12).
The MAX1233/MAX1234 can accept an external refer-
ence connected to REF for ADC conversion.
External ReferenceThe MAX1233/MAX1234 can accept an external refer-
ence connected to the REF pin for ADC conversions.
The internal reference should be disabled (RES1 = 1)
when using an external reference. At a conversion rate
of 50ksps, an external reference at REF must deliver up
to 15µA of load current and have 50Ωor less output
impedance. If the external reference has high output
impedance or is noisy, bypass it close to the REF pin
with a 0.1µF capacitor.
Selecting Internal or External ReferenceSet the type of reference being used by programming
the ADC control register. To select the internal refer-
ence, clock zeros into bits [A/D3:A/D0] and a zero to bit
RES1, as shown in the Control Registerssection. To
change to external reference mode, clock zeros into
bits [A/D3:A/D0] and a one to bit RES1. See Table13
for more information about selecting an internal or
external reference for the ADC.
Reference Power Modes
Auto Power-Down Mode (RES1 = RES0 = 0)The MAX1233/MAX1234 are in auto power-down mode
at initial power-up. Set the RES1 and RES0 bits to zero
to use the MAX1233/MAX1234 in the auto power-down
mode. In this mode, the internal reference is normally
off. When a command to perform a battery measure-
ment, temperature measurement, or auxiliary input
measurement is written to the ADC control register, the
device powers on the internal reference, waits for the
internal reference to settle, completes the requested
scan, and powers down the internal reference. The ref-
erence power delay depends upon the ADC resolution
selected (see Table8). Do not bypass REF with an
external capacitor when performing scans in auto
power-down mode.
Full-Power Mode (RES1 = 0, RES0 = 1)In the full-power mode, the RES1 bit is set LOW and
RES0 bit is set HIGH. In this mode, the device is pow-
ered up and the internal ADC reference is always ON.
The MAX1233/MAX1234 internal reference remains fully
powered after completing a scan.
Internal ClockThe MAX1233/MAX1234 operate from an internal oscil-
lator, which is accurate to within 20% of the 10MHz
specified clock rate. The internal oscillator controls the
timing of the acquisition, conversion, touch-screen set-
tling, reference power-up, and keypad debounce times.
8-Bit DACThe MAX1233/MAX1234 have a voltage-output, true 8-bit
monotonic DAC with less than 1LSB integral nonlinearity
error and less than 1LSB differential nonlinearity error. It
requires a supply current of only 150µA (typ) and pro-
vides a buffered voltage output. The DAC is at midscale
code at power-up and remains there until a new code is
written to the DAC register. During shutdown, the DAC’s
output is pulled to ground with a 1MΩload.
The internal DAC can be used in various system applica-
tions such as LCD/TFT-bias control, automatic tuning
(VCO), power amplifier bias control, programmable
threshold levels, and automatic gain control (AGC).
The 8-bit DAC in the MAX1233/MAX1234 employs a
current-steering topology as shown in Figure5. At the
core of this DAC is a reference voltage-to-current con-
verter (V/I) that generates a reference current. This cur-
rent is mirrored to 255 equally weighted current
sources. DAC switches control the outputs of these cur-
rent mirrors so that only the desired fraction of the total
current-mirror currents is steered to the DAC output.
The current is then converted to a voltage across a
resistor, and the output amplifier buffers this voltage.
DAC Output VoltageThe 8-bit DAC code is binary unipolar with 1LSB =
(VREF/256). The DAC has a full-scale output voltage of
(0.9 ×AVDD- 1LSB).
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
Output BufferThe DAC voltage output is an internally buffered unity-
gain follower that slews at up to ±0.4V/µs. The output
can swing from zero to full scale. With a 1/4FS to 3/4FS
output transition, the amplifier output typically settles to
1/2LSB in less than 5µs when loaded with 10kΩin par-
allel with 50pF. The buffer amplifier is stable with any
combination of resistive loads >10kΩand capacitive
loads <50pF.
Power-On ResetAll registers of the MAX1233/MAX1234 power up at a
default zero state, except the DAC data register, which
is set to 10000000, so the output is at midscale.
Keypad Controller and GPIOThe keypad controller is designed to interface a matrix-
type 4 rows ×4 columns (16 keys or fewer) keypad to a
host controller. The KEY control register controls keypad
interrupt, keypad scan, and keypad debounce times.
The KeyMask and ColumnMask registers enable mask-
ing of a particular key or an entire column of the keypad
when they are not in use. The MAX1233/MAX1234 offer
two keypad data registers. KPData1 holds all keypad
scan results, including masked data, and is thus the
pending register. KPData2 holds keypad scan results of
only the unmasked keys. If 12 or fewer keys are being
monitored, one or more of the row/column pins of the
MAX1233/MAX1234 can be software programmed as
GPIO pins.
Touch-Screen DetectionTouch-screen detection can be enabled or disabled by
writing to the ADC control register as shown in Table4.
Touch-screen detection is disabled at initial power-up.
Once touch-screen detection is enabled, the Y- driver
is on and the Y- pin is connected to GND. The X+ pin is
internally pulled to AVDDthrough a 1MΩresistor as
shown in Figure6. When the screen is touched, the X+
pin is pulled to GND through the touch screen and a
touch is detected.
When the 1MΩpullup resistor is first connected, the X+
pin can be floating near ground. To prevent false touch
detection in this case, the X+ pin is precharged high for
0.1µs using the 7ΩPMOS driver before touch detection
begins.
Key-Press DetectionKey-press detection can be enabled or disabled by
writing to the keypad control register as shown in Table
17. Key-press detection is disabled at initial power-up.
Once key-press detection is enabled, the C_ pins are
internally connected to DVDD and the R_ pins are inter-
nally pulled to GND through a 16kΩresistor. When a
key is pressed, the associated row pin is pulled to
DVDDand the key press is detected. Figure7shows
the key-press detection circuitry.
Interrupts
PEN Interrupt Request (PENIRQ)The PENIRQoutput can be used to alert the host con-
troller of a screen touch. The PENIRQoutput is normally
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controllerhigh and goes low after a screen touch is detected.
PENIRQreturns high only after a touch-screen scan is
completed. PENIRQdoes not go low again until one of
the touch-screen data registers is read. Figures8aand
8b show the timing diagrams for the PENIRQpin.
Keypad Interrupt Request (KEYIRQ)The KEYIRQoutput can be used to alert the host con-
troller of a key press. The KEYIRQoutput is normally
high and goes low after a key press is detected.
KEYIRQreturns high only after a key-press scan is
completed. KEYIRQdoes not go low again until one of
the key-press data registers is read. Figures 9a and 9b
show the timing diagrams for the KEYIRQpin.
Busy Indicator (BUSY)BUSYinforms the host processor that a scan is in
progress. BUSYis normally high and goes low and
stays low during each functional operation. The host
controller should wait until BUSYis high again before
using the serial interface.
Digital InterfaceThe MAX1233/MAX1234 interface to the host controller
through a standard 3-wire serial interface at up to
10MHz. DIN and CSare the digital inputs to the
MAX1233/MAX1234. DOUT is the serial data output.
Data is clocked out at the SCLK falling edge and is high
impedance when CSis high. PENIRQand KEYIRQcom-
municate interrupts from the touch-screen and keypad
controllers to the host processor when a screen touch or
a key press is detected. BUSYinforms the host proces-
sor that a scan is in progress. In addition to these digital
I/Os, the row and column pins of the keypad controller
can be programmed as GPIO pins.
Communications ProtocolThe MAX1233/MAX1234 are controlled by reading from
and writing to registers through the 3-wire serial inter-
face. These registers are addressed through a 16-bit
command that is sent prior to the data. The command
is shown in Table2.
The first 16 bits after the falling edge of CScontain the
command word. The command word begins with an
R/Wbit, which specifies the direction of data flow on
the serial bus. Bits 14 through 7 are reserved for future
use. Bit 6 specifies the page of memory in which the
desired register is located. The last 6 bits specify the
address of the desired register. The next 16 bits of data
are read from or written to the address specified in the
command word. After 32 clock cycles, the interface
automatically increments its address pointer and con-
tinues reading or writing until the rising edge of CS, or
until it reaches the end of the page.
Table 2. Command Word Format
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad ControllerIn order to read the entire first page of memory, for
example, the host processor must send the
MAX1233/MAX1234 the command 0x8000H. The
MAX1233/MAX1234 then begin clocking out 16-bit data
starting with the X-data register. In order to write to the
second page of memory, the host processor sends the
MAX1233/MAX1234 the command 0x0040H. The suc-
ceeding data is then written in 16-bit words beginning
with the ADC control register. Figures 10a and 10bshow
a complete write and read operation, respectively,
between the processor and the MAX1233/MAX1234.
Memory MapThe MAX1233/MAX1234s’ internal memory is divided
into two pages—one for data and one for control, each
of which contains thirty-two 16-bit registers.
Control RegistersTable3provides a summary of all registers and bit
locations of the MAX1233/MAX1234.
ADC Control RegisterThe ADC measures touch position, touch pressure, bat-
tery voltage, auxiliary analog inputs, and temperature.
The ADC control register determines which input is
selected and converted. Tables 4and 5show the for-
mat and bit descriptions for the ADC control register.
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
Bits 14-15: Pen Interrupt Status and
ADC Status BitsThese bits are used to control or monitor ADC scans.
Bits 10-13: ADC Scan SelectThese bits control which input to convert and which con-
verter mode is used. The bits are identical regardless of a
read or write. See Table7for details about using these bits.
Bits 8-9: ADC Resolution ControlThese bits specify the ADC resolution and are identical
regardless of read or write. Table8shows how to use
these bits to set the resolution.
Bits 6-7: Converter Averaging ControlThese bits specify the number of data averages the
converter performs. Table9shows how to program for
the desired number of averages. When averaging is
used, ADSTS and BUSYindicate the converter is busy
until all conversions needed for the averaging finish.
These bits are identical, regardless of read or write.
Bits 4-5: ADC Conversion Rate ControlThese bits specify the internal conversion rate, which
the ADC uses to perform a single conversion, as shown
in Table10. Lowering the conversion rate also reduces
power consumption. These bits are identical, regard-
less of read or write.
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
