2000 Nov 27 9
Philips Semiconductors Product specification
Sensor Conditioning Electronic UZZ9001
Table 4 Programming of trim modes
MODE
STATUS BITS
12345
enter trim mode for sensor input channel 1 0 0 0 1 0
enter trim mode for sensor input channel 2 0 0 1 0 0
leave trim mode for either input channel 0 0 0 0 0
How to enter the trim mode
Details of voltage levels and timing of the status bits to be
transmitted to the UZZ9001 are given in Table 3. Note that
a complete protocol has to be sent before normal
operation can be resumed. The trim mode can also be
exited by resetting the device. After entering one of the trim
modes and provided there is a dynamic input signal there
will be a square wave output at the terminal T
OUT
(pin 22).
Reset
In addition to the external reset pin (pin 6), the UZZ9001
provides an internal power-up/ power-down reset logic
which continuously monitors the supply voltage. When the
supply voltage increases and reaches a safe level, reset
becomes inactive and the device starts initialization. When
the supply voltage exceeds the safe voltage level, the
device is reset immediately. This internal reset logic can be
over-ridden in all modes and at any time by applying an
external active high command to the RES input pin (pin 6)
in all modes and at any time. The reset pin RES (pin 6).
This pin is internally pulled to ground and therefore need
not be connected if the function is not required.
Measurement dynamics
The UZZ9001 includes an on-chip RC Oscillator that
generates the clock for the whole device. Consequently,
no external clock supply is required for the measurement
system. The nominal clock frequency of the on-chip
oscillator is 4 MHz at room temperature. It varies with
temperature change. At −40 °C the clock frequency may
decrease to 2.3 MHz. At higher temperatures however,
a frequency up to 5.7 MHz may occur. This influences the
dynamics of measurements. From an application point of
view, two different effects have to be distinguished. The
system delay, which means how long it takes until a
changed input signal is recognized at the output, and the
measurement update rate. The system delay is mainly
caused by the settling time of the low pass decimation
filter, which depends on the maximum frequency content
(shape) of the input signals and the clock frequency. The
following maximum values can be expected for the entire
system delay. The measurement update rate, however, is
directly related to the oscillator frequency. At room
temperature, a new value is available every 0.26 ms.
When taking the entire temperature range into account,
update rates between 0.45 and 0.18 ms are possible.
(see Table 5)
