Passport 2®/Passport 2 LT™ Service Manual 0070-10-0441 2 - 27
Theory of Operation NIBP Module (P/N 0997-00-0501)
2.4.12 CMOS EEPROM
The HC16Z1 also has access to a National Semiconductor NM25C020 2k-bit serial
EEPROM through its QSPI port. This EEPROM device may be used for storing PCB
identification codes or any other non-volatile information. Although a potentiometer is
currently included in the circuitry to allow span calibration of the measurement channel, the
EEPROM could optionally be used to store span calibration values for a software calibration
scheme.
The HC16Z1 software can detect bad sector data in the serial EEPROM by storing
checksums which can be verified during initialization.
2.4.13 Voltage Sources
The PCB is fed 12V and 5V (VCC) from the host through connector J1. VCC is used to power
the PCB’s digital circuitry. It is also used to generate a 2.5V reference signal (25VR) using a
Maxim MAX6125 2.5V reference (U11).
VCC can alternately be applied through J7 during in-circuit programming or debugging
procedures. VCC shall not be applied to both connectors simultaneously. VPP is applied
through J7 as the programming voltage for the PIC16.
A switched version of 12V2 (12VSW) is generated by Q2 and is used to drive the electro-
mechanical components. This switch allows these components to be de-energized by the
PIC16 processor during an emergency shutdown. The 12V supply is also used to generate
separate, high tolerance 5 volt analog voltages, A5V and T5V, for powering the two
pressure transducer circuits. Each of these 5V voltages are generated using Maxim
MAX6250 5V references (U3 & U15).
A5V is used for the measurement channel pressure transducer and AD7714 ADC analog
supply and a divided version is used for the device reference. A5V is also used to power the
linear valve opamp control circuit.
T5V is used as the PIC16 ADC and HC16Z1 ADC reference voltages and the over-pressure
transducer supply. In addition, T5V is used as the HC16Z1 analog supply voltage (VDDA).
To Next Page
Loading...
