Philips PageWriter TC70 - +5 V; USB4_VCC; VM; VCC_PRNHD

Power System Overview Theory of Operation
PageWriter TC 70 Cardiograph Service Manual 8-13
+5V
Output from regulator U1401 (LTC1628) which supplies all the 5.V power to the system.
Input is from Load_PWR, and output is 4.87 to 5.24 VDC with a maximum current of 3A.
This voltage is monitored.
USB4_VCC
Output from switch U702 (LM3525) which supplies the PIM power. Input is from +5V, and
output is 5V with maximum current of 1.0A. This voltage is monitored.
VM
Output from regulator U1501 (LM2588), which supplies +26V power to the print head and
motor. This voltage is not monitored.
VCC_PRNHD
Output from switch Q1503, which supplies +26V power to the print head. It is controlled by
FPGA on the main board. VCC_PRNHD provides power only when a print session starts.
Otherwise, VCC_PRNHD does not provide power. This voltage is monitored byFPGA.
VCC_MOTOR
Output from switch Q1501, which supplies +26V power to the print motor. It is controlled by
FPGA on the main board. VCC_MOTOR provides power only when a print session starts.
Otherwise, VCC_MOTOR does not provide power. This voltage is not monitored.
VCC_BKLGT
Output from regulator U1504 (LTC3780), which supplies display backlight. Input is from
Load_PWR and output is 12V with a maxim current of 3.5A.
Power Management
Power Modes Control
The system host processor controls transition between power modes, including:
 Entering standby mode if no activity is detected for a preset period of time (upon
configuration).
 Powering off the unit if no activity is detected for a preset period of time (upon
configuration).
 Entering standby mode or off mode, when battery remaining capacity is below preset level
and no AC power is applied.