Service Manual

4-6 Model 340 Telemetry System Revision A
2006920-001
Theory of Operation: Transmitter Board (No. 2003708-001)
Power Supply
The main power supply for this system is a boot converter/regulator. This
switcher converts the battery voltage to a regulated 6.5 V over a battery
range of 3 to 6 V. The switching frequency of this regulator is
synchronized to a division of the main clock (575 kHz) to reduce noise
that might interfere with operation of the ultrasound circuit. A regulated
–6V supply is generated off this supply using a charge pump/regulator.
This converter is also synchronized to a division of the main clock (18
kHz) to prevent noise. Additional linear regulators operate off the 6.5 V
to generate the +6 V and +5 V required by the system. For noise
considerations, the ultrasound circuitry operates from separate +6 V, +5
V, and +2.5 V regulators.