Cardinal Health IVAC 571, Technical & Service Manual

Page: 45 / 104

IVAC® Volumetric Pump (Models 571 & 572) 45/104 1000SM00018 Issue 2
Circuit Descriptions
Module Overview Functional Description
The IVAC® Volumetric Pump, Models 571 and 572 are designed to be serviced generally to major assembly level.
The main circuitry within the pump is contained on five printed circuit boards (PCBs): Logic PCB, Power Regulator PCB,
Display PCB, Accessory Interface PCB, Analog PCB and a switch panel.
Cardinal Health will make available, on request, circuit diagrams which will assist appropriately qualified technical
personnel to repair those parts of the device which are designated by the manufacturer as repairable.
Logic PCB
Contains the main processor module, memory circuits, I/O
circuits and associated support circuitry which provide
the control functions for almost all the aspects of the
pump. It drives and monitors all other modules using the
program code stored in the EPROM and the RAM ICs.

Main Processor
Consists of an 8-bit microcontroller with an internal
clock generator, vectored interrupts and 64k byte
addressing capability. The processor gets instructions
from the program memory (EPROM U1 and RAM U28,
U29) and then executes them.

Power Control Circuit (& On/Off Switch)
Consists of flip flop (U18) and gate (U17) which are
powered from the VRAM supply so are operational
even when the pump is off. The ON/OFF switch
enables power to the system. It uses a single push
switch on the front panel to toggle the flip flop (U18).
Note if the battery voltage falls below 10.2V, the
microprocessor asserts the OFF signal to toggle U18
into the power-off condition as if the ON/OFF switch
has been pressed.

Wait-State Generator

Memory Address Decoder
Decoding used to select EPROM U13 and RAMs U28
and U29 is provided by various logic circuits.

Read Only Memory (ROM)
The software program is stored in ROM (U13).

Electrically Erasable Programmable Read Only
Memory (EEPROM)
U27, a 128 byte EEPROM is used to retain important
user information such as calibration constants and
operating parameter configurations.

Random Access Memory (RAM) and RAM test
U28 is the read/write memory type and a second RAM,
U29, and various ICs form a hardware RAM test circuit.

I/O Decoding

A/D Converter

Analog Input Signals

Output Ports/Input Ports

Programmable Interval Timer

Data Bus Buffer
Power Regulator PCB
The Power Regulator PCB provides system power supplies,
AC line and battery charging functions, motor control,
watchdog and alarm driver circuits.

Transformer, Rectifier and Filter

Line Regulator
Performs two functions, it is the main power source
when the pump is connected to AC power and it keeps
the battery charged by providing a nominal charge
voltage of 2.35V per cell. The circuit uses an integrated
circuit (U1) , configured as a fixed-frequency pulse
modulation regulator.

AC Line Indicator

AC Power Signal

Power Control Circuitry

+5L Regulator

5.12V Reference and VRAM Regulator

5V Switching Regulator

Clock/Dividing Chain
Crystal Y1, with associated components form a crystal
oscillator which clocks a binary counter. This counter
provides a signal which in turn drives certain circuitry
such as the watchdog alarm and provides timing for the
line regulator and motor control circuitry.

Watchdog
Watchdog pulses enable this circuit to perform an
integrity check on the microprocessor, generating an
alarm if pulses are not received within a defined timing
window.

Alarm Circuitry

Motor Control Circuitry
The microprocessor drives the motor by stepping the
current through each motor winding in the correct order
to cause the motor shaft to turn. Digital signals from
the Logic PCB determine the direction and duration of
the current and the winding is increased/decreased to
ensure sufficient torque to move the mechanism and
to hold its position. The motor control circuit controls
current across a bridge to the windings of the stepper
motor using a pulse width modulation technique.
Battery
The sealed lead acid battery pack consists of six cells each
with a potential of 1.8V to 2.40V, connected in series, a clad
fuse (F2), and a 1.5A fuse (F1). The battery pack is rated at
2.5 Ah at 12 VDC.