HP 220 - Manual (Page 60)

5Ć28 Functional Overview C3187Ć90000
Power Components
The following are the power components on the main PCA:
Carriage and Media Motor Drivers
Two motor driver ICs and heatsinks.
PrintĆCartridge Voltage Regulator
To regulate the amount of energy given to the printĆcartridge heating resistors, a precise
voltage regulator controls the printĆcartridge voltage supply. The regulator power device is
located on the main PCA, but the cartridge resistors and drivers are located on the carriage
PCA. To reduce the effect of the long path between the voltage regulator output and the
cartridge resistors, an active sense circuit on the carriage PCA feeds back an error signal to
the main PCA. On the carriage PCA, the cartridge supply voltage is sensed by a precision
resistor divider and compared with 2.5V reference. This error is amplified, buffered, and
transmitted to the main PCA through the trailing cable. The voltage is regulated by a
regulator on a heatsink.
Fan Driver
The plotter electronics are cooled by a fan, which may be turned on and off by the main
processor. A twoĆpin connector is used for the fan. Pin 1 connects to the black wire of the fan
harness and to the drain of a driver FET on the Main PCA. Pin 2 connects to the red wire of
the fan harness and to +12V on the Main PCA.