MAX11802EWC+T Maxim Integrated Products, MAX11802EWC+T Datasheet - Page 20

IC TOUCH SCREEN CTLR 12-WLP

MAX11802EWC+T

Manufacturer Part Number
MAX11802EWC+T
Description
IC TOUCH SCREEN CTLR 12-WLP
Manufacturer
Maxim Integrated Products
Type
Resistiver
Datasheet

Specifications of MAX11802EWC+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-WLP
Voltage Supply Source
Single Supply
Sampling Rate (per Second)
105k
Resolution
11 bits
Interface Type
I2C, SPI
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
SMD/SMT
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Other names
MAX11802EWC+T
MAX11802EWC+TTR
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I
power dissipation condition is observed when the point
of contact is in the top left corner of the panel sensor.
The planar end-to-end resistance included in the cur-
rent path is minimal at this location. Keep the averaging
and panel settling durations to the minimum required
by the application when pressure measurements are
required. Table 3 summarizes the physical panel set-
tings for supported measurement types.
Figure 6 shows the internal circuitry in the
MAX11800–MAX11803 used to detect the presence of
a touch on the panel. The selection of the pullup resis-
tance value (R
durations of the rough pullup interval (PUR = low-
impedance pullup) and fine pullup interval (PUF = high-
impedance pullup) are user-defined.
The MAX11800–MAX11803 revert to the low-power
panel setup when placed in touch-detect mode (TDM).
Figure 6 shows the active panel drive switches (YMSW
and XPSW are omitted for simplicity). TSW is a dedicat-
ed pullup switch used in TDM. TSW is also used during
PUF and TDM. XPSW is activated during PUR periods.
TDRSEL allows the selection of an internal pullup resis-
tor value of either 50kΩ or 100kΩ.
The X and Y touch-screen plates create an open circuit
with no current flow in the panel when the panel is not
being touched. In this case, TOUCH (see Figure 6) is
low. When a touch causes contact between the panel X
and Y plates, a current path is created and TOUCH is
pulled high, as long as R
end-to-end resistance) is much lower than R
open-circuit panel plate resistances range from 200Ω
to 1000Ω.
The MAX11800–MAX11803 enter high-impedance
pullup mode (50kΩ or 100kΩ) when the panel is not
being touched. The device is idle in this mode until a
Table 3. Summary of Physical Panel Settings for Supported Measurement Types
Note: The ADC input is fully differential with the negative input internally connected to GND. The MAX11800–MAX11803 control
access to the PUR, PUF, TDM, and LPM, which do not require setup procedures.
U indicates unconnected node.
20
TDM or PUF
______________________________________________________________________________________
MODE
PUR
LPM
Z1
Z2
X
Y
Touch-Detect Modes and Options
TD
50kΩ or 100kΩ
= touch-detect resistance) and the
V
V
DD
ADC_IN
ADC_IN
DD
V
through
X+
U
U
DD
(10Ω)
PX
+ R
PY
(the sum of panel
GND
GND
GND
X-
U
U
U
U
2
TD
C/SPI Interface
. Typical
ADC_IN
V
V
V
Y+
U
U
U
DD
DD
DD
touch is detected. The YMSW and TSW transistors are
on, and the XPSW and PSW transistors are off. With no
touch present, the Y- input of the TSC is at ground and
the X+ input is at V
voltage of the TSW nMOS device. This is a low-power
mode in which no current is consumed until a panel
touch occurs. When a touch is present on the panel,
the touch-screen controller (TSC) X+ input is pulled low
by the touch panel plate resistance and the YMSW tran-
sistor. This causes TOUCH to assume a logic-high and
the devices either issue the TIRQ interrupt for direct
conversion modes (MAX11800–MAX11803) or begin
self-timed scans for autonomous conversion mode
(MAX11800/MAX11801).
The value of the user-defined R
characteristics of the panel. To ensure reliable
detection values, worst-case panel resistance must
be checked against R
R
capacitance determines how quickly the panel can
be switched from measurement modes back to
touch monitoring mode without reporting false
touches or erroneous tags due to panel settling.
Panel touch status is also required to tag data from a
completed scan and measurement operation. Following
each scan operation, the panel must be returned to
TDM to determine if the panel is still being touched and
if the data obtained during the scan operation should
be considered valid. This operation is required since
the panel cannot be monitored for the presence of a
touch during the scan and measurement procedure.
The MAX11800–MAX11803 must return to TDM after
completing a measurement and making a decision on
the touch status of the panel. The measurement proce-
dure is only completed upon resolution of the touch sta-
tus and when data is tagged and available for
readback. The characteristics of the return to TDM and
TD
and the panel (or external noise rejecting)
ADC_IN
GND
GND
GND
Y-
U
U
U
DD
- V
TD
TN
. The interaction between
, where V
REF+
X+
Y+
Y+
Y+
U
U
U
TD
TN
depends on the
is the threshold
REF-
X-
Y-
X-
X-

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