UC3842/UC3843/UC3844/UC3845
Electrical Characteristics
(Continued)
(V
CC
=15V, R
T
=10kΩ, C
T
=3.3nF, T
A
= 0°C to +70°C, unless otherwise specified)
Parameter
PWM SECTION
Max. Duty Cycle
Min. Duty Cycle
TOTAL STANDBY CURRENT
Start-Up Current
Operating Supply Current
Zener Voltage
I
ST
I
CC(OPR)
V
Z
I
CC
= 25mA
-
V
pin3
=V
pin2
=ON
-
-
30
0.45
14
38
1
17
-
mA
mA
V
D
(Max)
D
(Max)
D
(MIN)
UC3842/UC3843
UC3844/UC3845
-
95
47
-
97
48
-
100
50
0
%
%
%
Symbol
Conditions
Min.
Typ.
Max.
Unit
Adjust V
CC
above the start threshould before setting at 15V
Note:
1. Parameter measured at trip point of latch
2. Gain defined as:
∆V
pin1
A
= -----------------
,0
≤
V
pin3
≤
0.8V
-
∆V
pin3
3. These parameters, although guaranteed, are not 100 tested in production.
UC3842
Figure 1. Open Loop Test Circuit
High peak currents associated with capacitive loads necessitate careful grounding techniques Timing and bypass capacitors
should be connected close to pin 5 in a single point ground. The transistor and 5kΩ potentiometer are used to sample the
oscillator waveform and apply an adjustable ramp to pin 3.
4
FAIRCHILD [ FAIRCHILD SEMICONDUCTOR ]
