FSD210, FSD200
3
Pin Definitions
Pin Configuration
Figure 5. Pin Configuration (Top View)
Pin Number
Pin Name
Pin Function Description
1, 2, 3
GND
Sense FET source terminal on primary side and internal control ground.
4
Vfb
The feedback voltage pin is the inverting input to the PWM comparator with
nominal input levels between 0.5Vand 2.5V. It has a 0.25mA current source
connected internally while a capacitor and opto coupler are typically
connected externally. A feedback voltage of 4V triggers overload protection
(OLP). There is a time delay while charging between 3V and 4V using an
internal 5uA current source, which prevents false triggering under transient
conditions but still allows the protection mechanism to operate under true
overload conditions.
5
Vcc
FSD210
Positive supply voltage input. Although connected to an auxiliary
transformer winding, current is supplied from pin 8 (Vstr) via an internal
switch during startup (see Internal Block Diagram section). It is not until Vcc
reaches the UVLO upper threshold (8.7V) that the internal start-up switch
opens and device power is supplied via the auxiliary transformer winding.
FSD200
This pin is connected to a storage capacitor. A high voltage regulator
connected between pin 8 (Vstr) and this pin, provides the supply voltage to
the FSD200 at startup and when switching during normal operation. The
FSD200 eliminates the need for auxiliary bias winding and associated
external components.
7
Drain
The Drain pin is designed to connect directly to the primary lead of the
transformer and is capable of switching a maximum of 700V. Minimizing the
length of the trace connecting this pin to the transformer will decrease
leakage inductance.
8
Vstr
The startup pin connects directly to the rectified AC line voltage source for
both the FSD200 and FSD210. For the FSD210, at start up the internal
switch supplies internal bias and charges an external storage capacitor
placed between the Vcc pin and ground. Once this reaches 8.7V, the
internal current source is disabled. For the FSD200, an internal high voltage
regulator provides a constant supply voltage.
1
2
3
4
5
7
8
GND
GND
GND
Vfb
Vstr
Drain
Vcc
7-DIP
7-LSOP
