QT110-S Atmel, QT110-S Datasheet - Page 9

• Manufacturer Part Number: QT110-S
• Description: SENSOR IC TOUCH/PROXMTY 1CH8SOIC
• Manufacturer: Atmel
• Series: QTouch™r
• Type: Capacitiver

Specifications of QT110-S

• Rohs Status: RoHS non-compliant
• Touch Panel Interface: 1, 2-Wire
• Number Of Inputs/keys: 1 Key
• Resolution (bits): 14 b
• Data Interface: Serial
• Voltage Reference: Internal
• Voltage - Supply: 2.5V, 3.3V, 5V
• Current - Supply: 20µA
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Output Type: Logic
• Interface: 2-Wire
• Input Type: Logic
• Other names: 427-1001

Re2 functions to isolate the transient from the Vdd pin;
values of around 1K ohms are reasonable.
As with all ESD protection networks, it is crucial that the
transients be led away from the circuit. PCB ground layout is
crucial; the ground connections to D1, D2, and C1 should all
go back to the power supply ground or preferably, if
available, a chassis ground connected to earth. The currents
should not be allowed to traverse the area directly under the
IC.
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If the device is connected to an external circuit via a cable or
long twisted pair, it is possible for ground-bounce to cause
damage to the Out pin; even though the transients are led
away from the IC itself, the connected signal or power
ground line will act as an inductor, causing a high differential
voltage to build up on the Out wire with respect to ground. If
this is a possibility, the Out pin should have a resistance Re3
in series with it to limit current; this resistor should be as
large as can be tolerated by the load.