LQ
C
APACITANCE
TO
D
IGITAL
C
ONVERTER
QT300
Capacitance to Digital Converter (CDC) IC
Direct-to-digital conversion, 16 bits
Log response: Wide dynamic range
Outputs raw data to a host device
Single wire UART interface
Master or Slave mode SPI interface
Programmable clock speed
Turns objects into intrinsic touch sensors
One external sample capacitor to control gain
Multiple QT300’s possible on one SPI bus
Vss
4
DRDY
SCK
SNS1
1
8
Vdd
SDO
REQ / 1W
SNS2
QT300
2
3
7
6
5
The QT300 charge-transfer (“QT’”) IC is a self-contained Capacitance-to-
Digital-Converter (CDC) capable of detecting femotofarad level changes in
capacitance. While designed primarily for instrumentation applications, it can be used
also for touch control applications where signal processing is best handled by a host
MCU.
Primary applications include fluid level sensors, distance sensors, transducer
‘amplifiers’ for pressure and humidity sensing functions, material detectors, and other
uses requiring quantified capacitance data.
APPLICATIONS
Fluid level sensors
Prox sensors
Moisture detection
Position sensing
Transducer driver
Material sensors
Unlike other Quantum products, the QT300 does not process its acquired data. Its only result is raw, unprocessed binary
data which can be transmitted to a host via either a bidirectional SPI interface or a simple polled single wire UART type
interface. This allows the designer to treat the device as a capacitance-to-digital-converter (CDC) for measurement
applications. It is ideal for situations where there are unique signal processing requirements.
The device requires only a single sampling capacitor to function. The value of this capacitor controls the gain of the sensor,
and it can be adjusted over 2�½ decades of range from 1nF to 500nF. No external switches, opamps, or other components
are required.
The device operates on demand, and can be synchronized to allow several QT300’s to operate near each other without
cross-interference.
T
A
0 C to +70 C
-40
0
C to +85
0
C
0
0
AVAILABLE OPTIONS
SOIC
-
QT300-IS
8-PIN DIP
QT300-D
-
LQ
Copyright © 2002 QRG Ltd
QT300 R1.01 21/09/03
QUANTUM [ QUANTUM RESEARCH GROUP ]
