MAX11800ETC/V+T Maxim Integrated Products, MAX11800ETC/V+T Datasheet - Page 21

• Manufacturer Part Number: MAX11800ETC/V+T
• Description: IC TOUCH SCREEN CTRLR LP 12WQFN
• Manufacturer: Maxim Integrated Products
• Type: Resistiver

Specifications of MAX11800ETC/V+T

• Touch Panel Interface: 4-Wire
• Number Of Inputs/keys: 1 TSC
• Resolution (bits): 12 b
• Data Interface: Serial, SPI™
• Data Rate/sampling Rate (sps, Bps): 105k
• Voltage - Supply: 1.7 V ~ 3.6 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 12-WQFN Exposed Pad
• Voltage Supply Source: Single Supply
• Sampling Rate (per Second): 105k
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

the timing of the decision are configurable through the
touch-detect pullup timing configuration register (0x07).
Program the MAX11800–MAX11803 in the context of
the application to maximize power efficiency and
achieve the desired scan throughput.
PUR is a fast pullup mode, which uses the main X+
switch in parallel with the resistive pullup to quickly slew
the panel capacitance. PUF uses only the touch-detect
pullup resistor, R
tion as TDM, but are timed so that the panel can settle
after completing measurements and before rendering
any decisions on the touch status of the panel.
Use the optional PUR mode to reduce the time to tag
data by momentarily placing the panel in a low-imped-
ance (< 10Ω) pullup mode instead of using the avail-
able 50kΩ/100kΩ touch-detection pullup resistors. This
operation forces the monitored TSC input high during
the PUR interval. Once the PUR interval expires, a PUF
interval must be allowed so that the panel can recover
and pull the TSC input low in case a touch is present.
The purpose of the PUR mode is to reduce the time
required to determine touch status by avoiding long
pullup time constants caused by high-capacitance
touch panels and the high-impedance on-chip pullup
resistors (R
intervals, the current through the low-impedance pullup
(XPSW) and panel combination is significantly higher
than that observed in the PUF mode. The durations in
Figure 6. Touch-Detection Circuitry
Low-Power, Ultra-Small Resistive Touch-Screen
X-
Y+
PANEL
TD
). When a touch is present during PUR
TD
______________________________________________________________________________________
. PUR and PUF serve the same func-
YMSW
XPSW
X+
Y-
V
DD
PUR
PUR, PUF, TDM
RTD
TSW
PSW
Controllers with I
RTD
PUR, PUF, TDM
TDRSEL
PUR and PUF
MAX11800–
MAX11803
MAX11801 LOGIC)
(TO MAX11800/
TOUCH
the PUR mode should be matched to the panel charac-
teristics and the desired scan throughput rates to mini-
mize power dissipation.
While use of the PUR mode is optional, the PUF period
is required for all applications. The PUF interval allows
the panel to resettle following scan or optional PUR
intervals. When a touch is not present, the panel capac-
itance settles toward V
switch and a portion of the panel resistance (with the
optional PUR mode disabled). When a touch is present,
the panel capacitance settles toward ground through a
portion of the panel resistance, ideally significantly
lower than the selected pullup impedance, R
enough recovery time for settling through the panel
resistance when using a PUR mode. Figure 7 illustrates
the touch-detection operations.
Once the PUF period expires, the preceding measure-
ment data is tagged and made available for readback.
The MAX11800–MAX11803 transition to an appropriate
mode depending on the conversion and interrupt mode
selected.
The MAX11800–MAX11803 contain a programmable
averaging filter. When enabled, this feature allows col-
lecting 4, 8, or 16 consecutive samples for each mea-
surement type requested. The number of the samples
for each measurement type is controlled by configura-
tion register 0x03. Averaging can be assigned to each
measurement type. For example, X and Y measure-
ments can use an average of 16 samples, while Z mea-
surements can use one or four samples to save power.
The AUX depth is selected in configuration register
0x0A.
The MAX11800–MAX11803 can be configured to per-
form one of two statistical operations. One option is a
median averaging filter (MAF). The MAF first removes
the lowest and highest values before averaging the
remaining sample set. The second filter type is a
straight averaging filter (SAF), which takes the average
of the entire sample set. Both filter types and
position/pressure averaging are controlled by configu-
ration register 0x0B. Table 4 presents the details of the
median averaging operations of the MAX11800–
MAX11803. For the MAX11800/MAX11801, averaging is
supported in both direct conversion mode and
autonomous conversion mode. The MAX11802/
MAX11803 support only direct conversion mode.
MAX11800–MAX11803 Averaging Modes
2
C/SPI Interface
Features Available in the
DD
through the internal pullup
Idle Modes
TD
. Allow
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