DA6512.000

11 July, 2012

9 (26)

This register is used to reset all control registers

no data bits in this register. However it is necessary

to write dummy data to this register to make a reset.

The reset will take place immediately after any data

or SPI interface.

and the internal clock oscillator is used for all the

measurements.

The SEL_EXTCLK bit enables the use of an

external clock signal connected to the OSCOUT

pin. This may come necessary if the sensor

capacitance is too high to be used with the internal

200kHz clock signal. Sensor capacitances up to

around 20pF can be measured with the internal

200kHz oscillator, or up to 40pF if the internal clock

frequency is divided by two (see SOSCOUT below).

By setting the SOSCOUT bit it is possible to divide

the internal clock oscillator frequency by two, giving

a 100kHz frequency. This lower clock frequency can

be

used

for

measuring

up

to

about

40pF

capacitances. For measuring larger than 40pF

external clock frequency having a frequency of

frequency division selection SOSCOUT applies only

to the internal clock signal.

The STEST bits are used for connecting different

internal signals to the TEST1 and TEST2 pins. In

STEST[2:0]=101 test setup TEST1 and TEST2

operate as voltage inputs which are connected to

the differential input of the

Σ-ADC. VTESTP is the

positive input and VTESTN is the negative input of

the Σ-ADC.

FOSC can be used to force the internal oscillator to

be on all the time. Normally the internal oscillator is

turned on only during the measurements to save

power.

Table 2.

Bit

Number

Bit Name

Description

Value

Function

7-6

-

Not used

-

-

5

SEL_EXTCLK

Selects external clock

0

1

Normal mode

An external clock can be

connected to OSCOUT and the

internal oscillator is disabled

4-2

STEST[2:0]

TEST1 and TEST2 signal

selection

Σ-ADC inputs connected to

TEST1 and TEST2 pins

000…100

101

110…111

Reserved for internal testing

purpose (TEST1 and TEST2

are outputs)

VTESTP => TEST1 (input)

VTESTN => TEST2 (input)

No function

1

SOSCOUT

Select OSCOUT frequency

0

1

OSCOUT = 200 kHz

OSCOUT = 100 kHz

0

FOSC

Forces the oscillator on

without conversion

0

1

OSC is on only during

conversion

OSC is forced on

X = Don’t care, SDM = Sigma delta modulator