PS081 datasheet(59/155 Pages) AMSCO

59 / 155 page

acam-messelectronic gmbh - Friedrich-List-Str.4 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de

4-2

PSØ81

Peripheral Components & Special Settings

4.1

Oscillators

PSØ81 has an internal low-current 10 kHz oscillator which is used for basic timer functions and for

the definition of the cycle time in stretched modes and measuring range 1.

Further, PSØ81 has an oscillator driver for an external 4 MHz ceramic resonator. This one is used

for the time measurement and for the definition of the cycle time in non-stretched modes. It needs

about 130 µA @ 3.0 V.

0 = Switch off oscillator

1 = oscillator continuously on

2 = Measurement started with 100 µs delay after switching on the oscillator

3 = Measurement started with 200 µs delay after switching on the oscillator

4 = Measurement started with 300 µs delay after switching on the oscillator

5 = Measurement started with 400 µs delay after switching on the oscillator 6

& 7 are not connected

Configuration:

This oscillator can be switched on continuously or only for the duration of the measurement, including

some lead time to reach the full oscillation amplitude (sel_start_osz[2:0]). The startup time for the

4MHz oscillator is about 50 µs to 100 µs and slightly depends on the supply voltage.

Auto-calibration:

The internal 10 kHz oscillator may be automatically calibrated by means of the 4 MHz oscillator. The

frequency varies with temperature and voltage. This would impact the update rate and sampling rate

as the 10 kHz is the basis for the TDC conversion counter and in stretched mode also the cycle

time. It is recommend to use the auto-calibration option setting auto10k = 1.

Note:

Auto-calibration should not be used in stretched single conversion modes

Layout Considerations:

The oscillator should be placed close to the PSØ81. The area arround the oscillator should be

flooded by a ground plane. The SPI wires should not cross the oscillator lines.

The 4 MHz should have an additional 1 MOhm pull-down resistor to avoid cross currents during

switch-off. The resistor reduces the oscillator current and is urgently needed in solar applications.

Member of the ams Group

PS081 Folha de dados(PDF) 59 Page - ams AG