TK75050DITL データシートの表示（PDF） - Toko America Inc
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TK75050DITL Datasheet PDF : 12 Pages
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TK75050
APPLICATION INFORMATION
START-UP
Figure 1 shows the application of the TK75050 smart
MOSFET driver in a self-biased power supply.
VIN
granted for use with the TK75050. For a detailed description
and application information of the Gate Charge Recovery
technique, see the Toko application note "Application
Considerations for a Smart Five-Pin MOSFET/IGBT Driver
with High-Speed Current-Limit Capability."
+
VCC
TK75050
+
PWM
CONTROLLER
FIGURE 1: TK75050 IN A SELF-BIASED POWER
SUPPLY
Figure 2 shows the typical waveforms during start-up.
UVLO UPPER THRESHOLD
UVLO LOWER THRESHOLD
VCC (t)
PWM ENABLE
BOOTSTRAP REGULATION
BEGINS
VUVLO (t)
VIN (t)
VIN (t) & VOUT (t)
UVLO
CONDITION
FIRST PULSE
CONDITION
DRIVER “WAKES UP”
VAUX
RF
VCC
IN
GND
IN
CF
OUT
OUT
PGND/CS
+
VCS (t)
-
VCS(t)
RCS
VCS(t)
0.95 V
CF IS CONNECTED TO GND
0.95 V
CF IS CONNECTED TO PGND/CS
(a)
(b)
FIGURE 3: CYCLE-BY-CYCLE CURRENT LIMIT WITH
THE TK75050
(a) SCHEMATIC
(b) WAVEFORMS
MAIN OVERLOAD PROTECTION IN VOLTAGE-
MODE-CONTROLLED CONVERTERS
Figure 4 shows the TK75050 in a voltage-mode-controlled
flyback converter. In this application example, the IC
provides the main overload protection.
+12 V
VIN
+
FIGURE 2: WAVEFORMS DURING START-UP
CYCLE-BY-CYCLE CURRENT LIMIT
Figure 3(a) shows how to use the TK75050 as a high-
speed cycle-by-cycle current limiter. Figure 3(b) shows the
waveforms. Note that the preferred connection for the
bottom terminal of the filter capacitor CF is to the PGND/CS
pin and not to the GND pin. By connecting CF to the PGND/
CS pin, the capacitive feedthrough of the drive signal that
would appear as a leading-edge spike in the current-sense
waveform is completely eliminated. This technique, called
"Gate Charge Recovery" is patented by Toko, Inc., but is
Page 8
FEEDBACK VOLTAGE-MODE
PWM
CONTROLLER
FIGURE 4: TK75050 IN A VOLTAGE-MODE-
CONTROLLED CONVERTER
January 1999 TOKO, Inc.
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