C2472, C2473 and C2474
Datasheet
RDFC Controllers for Offline Applications
Product data
Page 2 of 18
DS-1423-0709C
© Cambridge Semiconductor Ltd 2007
26-Sep-2007
PIN DEFINITIONS
Figure 2: C2472, C2473 and C2474 Pin Assignment
(drawings are not to scale)
VDD Pin
The VDD pin supplies power to the controller and is maintained at the correct voltage (nominally 3.3 V) by an
internal shunt regulator.
COL Pin
The COL pin is used to sense the collector voltage of the primary switching transistor, via a c oupling
capacitor, to control the timing and current levels of the signals produced on the BAS pin.
CS Pin
The CS pin senses the primary switch current via the current sensing resistor. The voltage sensed on this
pin is used to control the operating modes to manage standby and overload protection. Operating
characteristics are programmed via two external resistors.
AUX Pin
The AUX pin provides the supply current for the internal base driver block. In most applications, the AUX pin
is connected to the external supply rail via an NPN transistor and a current-limiting resistor to set the
maximum base current; however, in low power applications the AUX pin can be connected to the VDD pin
via the limiting resistor, with some compromise on the standby power consumption.
BAS Pin
The BAS pin switches the external bipolar primary switch transistor on and off. The current supplied to the
switch transistor is controlled to minimize the switching losses and thereby help optimize overall system
efficiency.
GND Pin
GND pins provide the ground reference. Where the device has multiple GND pins, all must be connected to
a common, low impedance path.
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