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| TL284XB Datasheet, PDF (11/24 Pages) Texas Instruments – HIGH-PERFORMANCE CURRENT-MODE PWM CONTROLLERS | |||
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www.ti.com
TL284xB, TL384xB
HIGH-PERFORMANCE CURRENT-MODE PWM CONTROLLERS
SLVS610B â AUGUST 2006 â REVISED JULY 2007
APPLICATION INFORMATION
The error-amplifier configuation circuit is shown in Figure 1.
2.5 V
Error
Amplifier
0.5 mA
Zi
VFB
+
â
Zf
COMP
A. Error amplifier can source or sink up to 0.5 mA.
Figure 1. Error-Amplifier Configuration
The current-sense circuit is shown in Figure 2.
IS
(see Note A)
Error
Amplifier
+
â
COMP
Rf
ISENSE
2R
R
1V
Current-Sense
Comparator
RS
Cf
GND
A. Peak current (IS) is determined by the formula: IS(max) = 1 V/RS
B. A small RC filter formed by resistor Rf and capacitor Cf may be required to suppress switch transients.
Figure 2. Current-Sense Circuit
The oscillator frequency is set using the circuit shown in Figure 3. The frequency is calculated as:
f = 1 / RTCT
For RT > 5 kâ¦:
f â 1.72 / RTCT
VREF
RT/CT
GND
RT
CT
Figure 3. Oscillator Section
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