MAX11800EWC+T Maxim Integrated Products, MAX11800EWC+T Datasheet - Page 24



Manufacturer Part Number
Maxim Integrated Products

Specifications of MAX11800EWC+T

Touch Panel Interface
Number Of Inputs/keys
Resolution (bits)
12 b
Data Interface
Serial, SPI™
Data Rate/sampling Rate (sps, Bps)
Voltage - Supply
1.7 V ~ 3.6 V
Operating Temperature
-40°C ~ 85°C
Mounting Type
Surface Mount
Package / Case
Voltage Supply Source
Single Supply
Sampling Rate (per Second)
11 bits
Interface Type
Supply Voltage (max)
3.6 V
Supply Voltage (min)
1.7 V
Conversion Rate
34.4 KSPs
Maximum Operating Temperature
+ 85 C
Minimum Operating Temperature
- 40 C
Mounting Style
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Other names
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I
The MAX11800/MAX11801 can perform measurements
automatically without the AP involvement, and is
referred to as autonomous conversion mode (ACM).
When operating in ACM, the MAX11800/MAX11801 use
an on-chip FIFO to store measurement results. As each
new data is written to the FIFO, an interrupt is generat-
ed. The AP can choose to service (read) the FIFO result
after each interrupt or wait until the FIFO is full then
read the entire FIFO contents at once. The AP can also
read the contents of the FIFO at any time. See the
Autonomous Conversion Mode section for a further
description of operations.
The MAX11800/MAX11801 contain a feature referred to
as aperture. It is only available on the MAX11800/
MAX11801 when operating in autonomous conversion
mode. The aperture feature creates an invisible rectan-
gle around a touch location within the MAX11800/
MAX11801 hardware. The size of the rectangle is user
programmable. One application of the aperture feature
is to provide “spatial hysteresis.” Spatial hysteresis can
be useful for applications that require lower resolution
touch accuracy without requiring the AP to handle the
mathematics involved to filter out extraneous data.
Another application would be to use the aperture fea-
ture to implement simple single finger or stylus ges-
tures. See the Using Aperture Mode section for a
further description of operations.
To simplify measurement procedures, the MAX11800–
MAX11803 support three types of commands: panel
setup commands (PSU), panel measurement commands
(PMC), and combined measurement commands (CMC).
In direct conversion mode, the MAX11800/MAX11801
can use all three types of commands. Using individual
panel setup and measurement commands allow for a
high degree of customization based on decisions made
by the AP, while using combined commands signifi-
cantly simplifies the complete measurement process
and reduces communications between the AP and the
In autonomous mode, the MAX11800/MAX11801 use
combined commands to control and automate all
aspects of panel setup, measurements, and timing. See
the Operating Mode Configuration Register (0x0B) sec-
tion for more details.
Panel Setup, Measurement, and Scan Commands
MAX11800/MAX11801 Only
Features Available in the
Autonomous Mode
C/SPI Interface
In direct conversion mode, the AP requests individual
panel setup and conversion operations or automated
combinations of measurements (X and Y, X and Y and
Z1, or X and Y and Z1 and Z2 combined). Unlike
autonomous conversion modes, the AP maintains control
over the initiation of panel setup, measurements events,
and the sampling frequency. Figure 8 shows the state
machine transitions for direct conversion mode.
The MAX11800–MAX11803 support two direct conver-
sion interrupt modes. The two direct conversion modes
are the continuous interrupt mode (CINT) and the edge
interrupt mode (EINT).
In continuous interrupt mode, the panel returns to TDM
and idle. The current status of the panel is then sent
through TIRQ. The continuous interrupt mode is the
least efficient mode in current consumption for long
duration of touches. The power consumption is approxi-
mated by P
tion levels observed when the panel is not touched is
limited by the junction leakage currents of the
Procedure: The MAX11800–MAX11803 idle in TDM.
The TIRQ output goes low when a touch is detected on
the panel indicating to the AP that a touch is present
and a measurement operation starts.
The AP requests specific panel measurements through
the serial interface. TIRQ stays low during panel setup
and measurement operations. Once a measurement is
complete (with the “continuous” bit, CONT = 0, see
Table 1), the MAX11800–MAX11803 check for the con-
tinued presence of a touch on the panel and tag the data
accordingly (see Table 6). The duration of this operation
is programmable, specified in the touch-detect pullup
timing configuration register (0x07). After the data is
tagged, the data is available for readback through the
serial interface. The MAX11800–MAX11803 return to
TDM and return control of TIRQ to the TDM circuitry.
TIRQ stays low while a touch remains present, indicating
further measurements are required, otherwise TIRQ goes
high until a new touch is observed.
Continuous interrupt mode (CINT) allows the complete
control over the measurement operations and direct obser-
vation of the touch status of the panel. Figure 9 shows the
polling of TIRQ when other functions share the TIRQ bus. In
the illustration of Figure 9, no ‘10’ event tag is observed
because the release occurs during a TDM period.
Direct Conversion Mode Operations
= V
Continuous Interrupt Mode
. The power consump-
Interrupt Modes

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