UC3844D Fairchild Semiconductor, UC3844D Datasheet - Page 6

• Manufacturer Part Number: UC3844D
• Description: IC CTLR PWM CURR MODE 14-SOIC
• Manufacturer: Fairchild Semiconductor

Specifications of UC3844D

• Pwm Type: Current Mode
• Number Of Outputs: 1
• Frequency - Max: 500kHz
• Duty Cycle: 50%
• Voltage - Supply: 11.5 V ~ 30 V
• Buck: No
• Boost: No
• Flyback: No
• Inverting: No
• Doubler: No
• Divider: No
• Cuk: No
• Isolated: No
• Operating Temperature: 0°C ~ 70°C
• Package / Case: 14-SOIC (3.9mm Width), 14-SOL
• Frequency-max: 500kHz
• Duty Cycle (max): 50 %
• Output Current: 1000 mA
• Mounting Style: SMD/SMT
• Switching Frequency: 500 KHz
• Operating Supply Voltage: 30 V
• Supply Current: 17 mA
• Maximum Operating Temperature: + 70 C
• Fall Time: 35 ns
• Minimum Operating Temperature: 0 C
• Rise Time: 45 ns
• Synchronous Pin: No
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: UC3844DFS

UC3842/UC3843/UC3844/UC3845
Oscillator timing capacitor, C
discharge time, the internal clock signal blanks the output to the low state. Selection of R
oscillator frequency and maximum duty cycle. Charge and discharge times are determined by the formulas:
t
Frequency, then, is: f=(t
6
c
t
= 0.55 R
D
ForRT
=
R
T
C
Figure 6. Oscillator Dead Time & Frequency
T
T
5K
I
n
C
T
0.0063R
--------------------------------------- -
0.0063R
,
f
=
(Deadtime vs C
-------------- -
R
1.8
T
C
T
c
T
T
–
+ t
–
2.7
4
d
)
T
-1
, is charged by V
Figure 5. Oscillator Waveforms and Maximum Duty Cycle
T
RT > 5k
Figure 8. Shutdown Techniques
REF
through R
T
and discharged by an internal current source. During the
Figure 7. Timing Resistance vs Frequency
T
and C
T
therefore determines both