E240B QUANTUM ATMEL, E240B Datasheet - Page 13
![QT240 4 Key Qtouch Evaluation Kit](/photos/24/8/240891/4651384_sml.jpg)
E240B
Manufacturer Part Number
E240B
Description
QT240 4 Key Qtouch Evaluation Kit
Manufacturer
QUANTUM ATMEL
Datasheet
1.E240B.pdf
(15 pages)
Specifications of E240B
Silicon Manufacturer
Atmel
Application Sub Type
Touch Sensor
Kit Application Type
Sensing - Touch / Proximity
Silicon Core Number
QT240
Kit Contents
Board And Literature
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
12
With Spread Spectrum enabled (factory default configuration), a sawtooth voltage signal is
generated on pin 9 (SYNC/SS) of the QT240; this is used to modulate the QT240’s burst
frequency. As pin 9 ramps up, the sample burst frequency increases. The effect of Spread
Spectrum operation is twofold:
These benefits are highly significant in all applications. The burst and spread modulation
waveforms are as shown:
The burst frequency centers at ~100KHz. The 2V SPREAD sawtooth causes the oscillator to
sweep about ±7% around the center frequency. If the burst length is adjusted (e.g. by changing
the Cs sample capacitors), the SPREAD signal may need to be tweaked to maintain the ±7%
sweep. The easiest way to do this is to change C9. For longer burst lengths, increase C9
(factory default value is 22nF, X7R type) to maintain a ~2V peak amplitude on the SPREAD
waveform.
- Peak EMC emissions are reduced by up to 10dB, and,
- The E240’s susceptibility to external interference is reduced by a similar amount.
SPREAD SPECTRUM