ZSSC3230BC2B datasheet(13/39 Pages) RENESAS

13 / 39 page

ZSSC3230 Datasheet

October 15, 2019

6.2

Capacitive Sensor Front-End

The capacitance amplifier input range (CRANGE) must be adjusted to the external capacitance conditions for signal (CSIGNAL) and offset shift

(COFFSET) as given in Equation 1. See Figure 6 for an illustration of the terms.

RANGE = COFFSET + CSIGNAL

Equation 1

COFFSET operates as a zero-shift capacitance to cancel a given offset by the sensor. The offset-shift capacitance must not exceed the selected

input capacitance range CRANGE. For COFFSET, the respective configuration must be set up in the EEPROM for the shift_cap parameter (bits[5:0]

in memory register 12HEX; see Table 16).

The correlating setup for CSIGNAL must be done in the EEPROM for parameter cap_range (bits[13:9] in memory register 12HEX). In Table 16, the

respective values are given. These values can be measured in the positive and negative direction, so the effective range of CSIGNAL will be

doubled compared to the cap_range setting. The principle is shown in Figure 6.

Figure 6. Capacitive Input Signal Conditions

ZSSC3230

VDD

VSS

SDA

SCL

RESQ

EOC

COFFSET

CSIGNAL

COFFSET

+ Capacitance Range

– Capacitance Range

Sensor Characteristic

CSIGNAL

COFFSET

CSIGNAL

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