TK75002DIMG/75002 データシートの表示（PDF） - Toko America Inc
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TK75002DIMG/75002 Datasheet PDF : 10 Pages
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PIN DESCRIPTION
VCC PIN
This pin is connected to the supply voltage. The operation
of the IC is enabled when the supply voltage exceeds
4.1 V, which is the upper threshold of the undervoltage
lockout circuit. The operation is disabled when the supply
voltage drops below 3.98 V.
GND PIN
This pin provides ground return for the IC.
DRV PIN
This pin drives the first terminal of the primary winding of
the external pulse transformer using pulse-amplitude
modulation (PAM). The second terminal of the primary
winding is connected to the VCC pin. When the DRV pin is
low, an internal NPN transistor (the PAM switch) is turned
on and sinks an increasing current from the supply voltage
through the primary winding. The PAM switch is turned off
when the current reaches approximately 55 mA. The PAM
switch is turned on again when the transformer is reset
through the internal free-wheeling diode.
INV PIN
The INV pin is the inverting input of the error amplifier. The
non-inverting input of the error amplifier is connected to an
internal 1.35 V precision reference source.
COMP PIN
The COMP pin is the output of the error amplifier. The
frequency compensation feedback network is connected
between the COMP and INV pins. Internally, the COMP pin
drives the inverting input of a level shifter stage. The roles
of the level shifter are to change (1) the reference point of
the error signal from the GND pin to the VCC pin (necessary
to avoid the parasitic zero in the transfer function caused
by feed-forward through the supply) and (2) the signal
polarity (necessary for start-up of the converter system in
case the reference point was changed). The parasitic zero
is discussed in the "Application Information" section.
January 1999 TOKO, Inc.
TK75002
Page 5
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