KA3511DS Fairchild Semiconductor, KA3511DS Datasheet - Page 8

• Manufacturer Part Number: KA3511DS
• Description: IC PWM/SECONDARY COMBO 22-DIP
• Manufacturer: Fairchild Semiconductor

Specifications of KA3511DS

• Pwm Type: Current Mode
• Number Of Outputs: 3
• Frequency - Max: 10kHz
• Duty Cycle: 50%
• Voltage - Supply: 14 V ~ 30 V
• Buck: No
• Boost: No
• Flyback: No
• Inverting: No
• Doubler: No
• Divider: No
• Cuk: No
• Isolated: No
• Operating Temperature: -25°C ~ 85°C
• Package / Case: 22-DIP (0.400", 10.16mm)
• Frequency-max: 10kHz
• Topology: Push-Pull
• Output Voltage: 40 V
• Output Current: 200 mA
• Switching Frequency: 10 KHz
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 25 C
• Fall Time: 50 ns
• Mounting Style: Through Hole
• Rise Time: 100 ns
• Synchronous Pin: No
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

6. BLOCK DESCRIPTION & APPLICATION INFORMATIONS
6.1 OSCILLATOR BLOCK
The KA3511 is a fixed-frequency pulse width modulation control circuit. An internal-linear sawtooth
oscillator is frequency-programmable by two external components, R
quency is determined by
6.2 PWM CONTROL BLOCK
Output pulse width modulation is accomplished by comparison of the positive sawtooth waveform
across capacitor C
Q1 and Q2, are enabled only when the flip-flop clock-input line is in its low state. This happens only
during that portion of time when the sawtooth voltage is greater than the control signals. Therefore,
an increase in control-signal amplitude causes a corresponding linear decrease of output pulse
width. (Refer to the timing diagram shown in Figure 4)
T
to either of two control signals. The NOR gates, which drive output transistors
Figure 2. Oscillator Frequency vs. Timing Resistance
Figure 1. Oscillator R
fosc
=
8
-------------------- -
R
T
1.1
C
T
T
, C
T
T
and C
T
. The oscillator fre-
Rev C, November 1999