STMPE24M31QTR STMicroelectronics, STMPE24M31QTR Datasheet - Page 49

• Manufacturer Part Number: STMPE24M31QTR
• Description: IC SENSOR S-TOUCH 24CH 40QFN
• Manufacturer: STMicroelectronics
• Series: S-Touch™r
• Type: Capacitiver

Specifications of STMPE24M31QTR

• Number Of Inputs/keys: 24 Key
• Data Interface: I²C
• Data Rate/sampling Rate (sps, Bps): 100k, 400k
• Voltage Reference: External
• Voltage - Supply: 1.65 V ~ 1.95 V
• Current - Supply: 900µA
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 40-VQFN
• Output Type: Logic
• Interface: I²C
• Input Type: Logic
• Supply Voltage: 1.8 V
• Number Of Channels: 24
• Dimensions: 5 mm L x 5 mm W x 0.85 mm H
• Temperature Range: - 40 C to + 85 C
• Termination Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 497-10380-2

STMPE16M31, STMPE24M31
13.1
13.2
Figure 14. Touch sensing module flowchart
Sampling rate calculation
The capacitive sensor operates with a 2 MHz base clock, a single capacitive sensor scans
up to 24 active channels.
The SCLK_DIV divides the sensor clock by 64-1024, giving 2 kHz-32 kHz sensor clock.
For capacitive sensing, a PRBS sequence is utilized to remove the effect of surrounding
noise. This PRBS has an average value of 4.5.
The effective total sampling rate is thus 2 kHz-32 kHz divided by 4.5, giving 440 Hz – 7 kHz.
If all 24 channels of capacitive sensors are active, the channel conversion rate is thus
440 Hz/24 = 18.3 Hz (Min), 7 kHz/24 =296 Hz (Max)
Using the maximum MAF setting (18 remove 2), the maximum filtered channel output rate is
296 Hz/18 = 16 Hz.
Sensor resolution
The capacitive sensor hardware in the STMPExxM31 devices has a sensitivity of 15 fF and
a range of 512 steps giving it a dynamic range of 7.5 pF.
Doc ID 16174 Rev 3
Touch sensor controller
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