UC3854N-F Datasheet, PDF (5/12 Pages) Texas Instruments – High Power Factor Preregulator

PIN DESCRIPTIONS (cont.)
GT Drv (Pin 16) (gate drive): The output of the PWM is a
totem pole MOSFET gate driver on GT Drv. This output is
internally clamped to 15V so that the IC can be operated
with VCC as high as 35V. Use a series gate resistor of at
least 5 ohms to prevent interaction between the gate im-
UC1854
UC2854
UC3854
pedance and the GT Drv output driver that might cause
the GT Drv output to overshoot excessively. Some over-
shoot of the GT Drv output is always expected when driv-
ing a capacitive load.
TYPICAL CHARACTERISTICS at TA = TJ = 25°C
Current Amplifier Gain and Phase vs Frequency
120
Phase
Margin ¹⁰⁰
degrees 80
60
Open-Loop ⁴⁰
Gain 20
dB
0
-20
0.1
1
10
100 1000 10000
Frequency
kHz
Voltage Amplifier Gain and Phase vs Frequency
120
Phase
Margin ¹⁰⁰
degrees 80
60
Open-Loop ⁴⁰
Gain 20
dB
0
-20
0.1
1
10
100 1000 10000
Frequency
kHz
Gate Drive Rise and Fall Time
700
600
500
ns
400
300
200
100
0
0
Rise Time
Fall Time
0.01
0.02
0.03
0.04
0.05
Load Capacitance, µF
Gate Drive Maximum Duty Cycle
100%
95%
90%
Duty
Cycle
85%
80%
75%
70%
1
10
100
RSET, k Ω
Multiplier Output vs Voltage on Mult
600
500
400
Multiplier
Output ₃₀₀
µA
200
Mult Out=3V
Mult Out=2V
Mult Out=1
Mult Out=0V
VRMS=2V, VA Out=5V
100
0
0 100 200 300 400 500 600 700 800
IAC, µA
Oscillator Frequency vs RSET and CT
1000
Frequency
kHz ₁₀₀
10
1
100pF
200pF
500pF
1nF
10nF 5nF 3nF ^2nF
10
100
RSET, k Ω
5