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Functional description
25.7.2.2 OpAMP descriptions
The on-chip amplifier is usually connected as a differential amplifier. Its gain is internally
set to 20. But the gain can be reduced by adding external resistors on its plus and minus
input, as shown in
Figure
25-3. it normally is used as current sense amplifier to sense the
current flowing through the external resistor shunt as a voltage across the resistor. In
order to measure both positive and negative currents, an internal bias reference must be
used. This reference is divided either VREFH or VDDX to a half and added it to positive
input of amplifier. The output of amplifier is connected to the ADC inputs and to the plus
input of limitation comparator which can be used as over current protection. The minus
input of limitation comparator is driven by a programmable 6-bit DAC. The output of the
comparator is connected to a digital filter circuit.
25.7.3 Predrive function descriptions
This section describes the MOSFET predriver.
25.7.3.1 Predrive diagram
The following figure shows the predrive diagram
MC9S08SU16 Reference Manual, Rev. 5, 4/2017
464
NXP Semiconductors
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