ISL6842 Intersil Corporation, ISL6842 Datasheet - Page 6

• Manufacturer Part Number: ISL6842
• Description: Improved Industry Standard Single Ended Current Mode PWM Controller
• Manufacturer: Intersil Corporation

Typical Performance Curves
Pin Descriptions
RTCT - This is the oscillator timing control pin. The
operational frequency and maximum duty cycle are set by
connecting a resistor, RT, between VREF and this pin and a
timing capacitor, CT, from this pin to GND. The oscillator
produces a sawtooth waveform with a programmable
frequency range up to 2.0MHz. The charge time, T
discharge time, T
maximum duty cycle, Dmax, can be calculated from the
following equations:
T
T
f
D
Figure 4 may be used as a guideline in selecting the
capacitor and resistor values required for a given frequency.
C
D
=
=
≈
≈
1
T C
0.583 RT CT
–
⁄
1.002
0.998
0.996
0.994
RT
(
T
1.02
1.01
0.99
0.98
0.97
FIGURE 3. EA REFERENCE vs TEMPERATURE
•
C
FIGURE 1. FREQUENCY vs TEMPERATURE
1
•
f
1
-40 -25 -10
-40
•
+
CT
T
D
•
)
•
ln
D


-10
0.0083 RT 4.3
----------------------------------------------
0.0083 RT 2.4
, the switching frequency, f, and the
TEMPERATURE (
5
TEMPERATURE (
•
•
20
20
–
–
6
35
50


50
o
o
C)
C)
65
ISL6842, ISL6843, ISL6844, ISL6845
80
80
95 110
110
C
(EQ. 1)
(EQ. 2)
(EQ. 3)
(EQ. 4)
, the
COMP - COMP is the output of the error amplifier and the
input of the PWM comparator. The control loop frequency
compensation network is connected between the COMP and
FB pins.
FB - The output voltage feedback is connected to the
inverting input of the error amplifier through this pin. The
non-inverting input of the error amplifier is internally tied to a
reference voltage.
CS - This is the current sense input to the PWM comparator.
The range of the input signal is nominally 0 to 1.0V and has
an internal offset of 100mV.
GND - GND is the power and small signal reference ground
for all functions.
OUT - This is the drive output to the power switching device.
It is a high current output capable of driving the gate of a
power MOSFET with peak currents of 1.0A. This GATE
output is actively held low when V
threshold.
FIGURE 2. REFERENCE VOLTAGE vs TEMPERATURE
1-10
1.001
0.999
0.998
0.997
0.996
0.995
100
10
1
1
3
-40 -25 -10
10
FIGURE 4. RTCT vs FREQUENCY
20
30
5
TEMPERATURE (
40
20
RT (kΩ)
50
35
60
DD
50
o
70
is below the UVLO
C)
65
80
80
90
95 110
100
CT=
100pF
220pF
330pF
470pF
1.0nF
2.2nF
3.3nF
4.7nF