STMPE821QTR STMicroelectronics, STMPE821QTR Datasheet - Page 9
![IC CTLR TOUCH KEY 8CH CAP 16-QFN](/photos/6/64/66486/stmpe821qtr_sml.jpg)
STMPE821QTR
Manufacturer Part Number
STMPE821QTR
Description
IC CTLR TOUCH KEY 8CH CAP 16-QFN
Manufacturer
STMicroelectronics
Type
Capacitiver
Specifications of STMPE821QTR
Number Of Inputs/keys
8 Key
Data Interface
I²C
Voltage - Supply
1.65 V ~ 1.95 V
Operating Temperature
-40°C ~ 85°C
Mounting Type
Surface Mount
Package / Case
16-QFN
Voltage Supply Source
Single Supply
Resolution
7 bit to 10 bit
Interface Type
I2C
Supply Voltage (max)
3.6 V
Supply Voltage (min)
2.7 V
Maximum Operating Temperature
+ 85 C
Minimum Operating Temperature
- 40 C
Mounting Style
SMD/SMT
Number Of Channels
8
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Sampling Rate (per Second)
-
Resolution (bits)
-
Lead Free Status / Rohs Status
Lead free / RoHS Compliant
Other names
497-8826-2
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Company:
Part Number:
STMPE821QTR
Manufacturer:
STM
Quantity:
1 261
STMPE821
1.4.1
1.4.2
Noise filtering
When the STMPE821 is operating in the vicinity of highly emissive circuits (DC-DC
converter, PWM controller/drive etc), the sensor inputs will be affected by high-frequency
noise. In this situation, the time-integrating function could be used to distinguish between
real touch, or emission-related false touch.
The INTEGRATION TIME and STRENGTH THRES registers are used to configure the time-
integrating function of STMPE821.
Data filtering
The output from the calibration unit is an instantaneous "TOUCH" or "NO TOUCH" status.
This output is directed to the filtering stage where the TOUCH is integrated across a
programmable period of time. The output of the integration stage would be a "STRENGTH"
(in STRENGTH register) that indicates the number of times a "TOUCH" is seen, across the
integration period.
The "STRENGTH" is then compared with the value in "STRENGTH THRESHOLD" register.
If STRENGTH exceeds the STRENGTH THRESHOLD, this is considered a final, filtered
TOUCH status.
In data filtering stage, 3 modes of operation is supported:
Mode 1: Only the “touch” channel with highest STRENGTH is taken
Mode 2: All the “touch” channels with STRENGTH > STRENGTH THRESHOLD is taken
Mode 3: The 2 “touch” channel with the highest STRENGTH is taken. These modes are
selected using the FEATURE SELECTOR register.
The final, filtered data is accessible through the Touch Byte register.
STMPE821 functional overview
9/55