KA3842B_02 Datasheet, PDF (4/10 Pages) Fairchild Semiconductor – SMPS Controller

KA3842B/KA3843B/KA3844B/KA3845B
Electrical Characteristics (Continued)
(VCC=15V, RT=10KΩ, CT=3.3nF, TA= 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
Symbol
D(Max)
D(MAX)
D(MIN)
IST
ICC(OPR)
VZ
Conditions
KA3842B/KA3843B
KA3844B/KA3845B
-
-
Vpin3=Vpin2=ON
ICC = 25mA
Min. Typ. Max. Unit
95 97 100 %
47 48 50 %
-
-
0
%
- 0.45 1 mA
-
14 17 mA
30
38
-
V
Adjust VCC above the start threshould before setting at 15V
Note:
1. Parameter measured at trip point of latch
2. Gain defined as:
A = ^∆-----^V----^p---ⁱ-ⁿ---¹-
∆V_pin3
,0 ≤ Vpin3 ≤ 0.8V
3. These parameters, although guaranteed, are not 100 tested in production.
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