NCP1271 ON Semiconductor, NCP1271 Datasheet - Page 3

• Manufacturer Part Number: NCP1271
• Description: Soft?skip? Mode Standby Pwm Controller With Adjustable Skip Level And External Latch
• Manufacturer: ON Semiconductor

PIN FUNCTION DESCRIPTION
Pin No.
R
1
2
3
4
5
6
8
skip
R
R
Skip/ latch
CS
ramp
Skip/latch
Symbol
Gnd
V
Drv
CS
CS
HV
FB
FB
Gnd
CC
4
2
3
1
10V
V
V
FB
I
CS
Supply Voltage
Current Sense
10V
10V
Skip Adjust or
Driver Output
skip
High Voltage
4.8 V
IC Ground
Function
Feedback
1
Latchoff
16.7k
75.3k
V
FB
0
/ 3
180 ns
V
V
LEB
1 / 3
skip
skip
0
= R
= 1.2 V when pin 1 is opened
jittered ramp
current source
8 V
Figure 2. Functional Block Diagram
2.85 V
skip
A resistor to ground provides the adjustable standby skip level. Additionally, if this pin is
pulled higher than 8.0 V (typical), the controller latches off the drive.
An optocoupler collector pulls this pin low during regulation. If this voltage is less than
the Skip pin voltage, then the driver is pulled low and Soft-Skip mode is activated. If this
pin is open (>3 V) for more than 130 ms, then the controller is placed in a fault mode.
This pin senses the primary current for PWM regulation. The maximum primary current
is limited to 1.0 V / R
resistor R
for improved stability.
-
The NCP1271's powerful output is capable of driving the gates of large Qg MOSFETs.
This is the positive supply of the device. The operating range is between 10 V (min) and
20 V (max) with a UVLO start threshold 12.6 V (typ).
This pin provides (1) Lossless startup sequence (2) Double hiccup fault mode (3)
Memory for latch-off shutdown and (4) Device protection if V
+
-
(1V max)
1
V
* I
+
-
V
PWM
skip
100uA
0
+
-
ss
TLD
http://onsemi.com
or
ramp
NCP1271
Soft start/ soft-skip
130ms
between the current sense node and this pin sets the compensation ramp
PWM
delay
7.5% Jittering
65, 100 kHz
Oscillator
+
-
management
4 ms/ 300 us
3
13 us filter
CS
disable
soft
skip
where R
V
V
&
skip
FB
CS
soft-skip
short
circuit
fault
is the current sense resistor. Additionally, a ramp
skip
+
-
soft
start
Description
S
R
OR
Q
Max duty
turn on internal bias
S
R
latch-off, reset
when Vcc < 4V
Counter
= 80%
4.1 mA when Vcc > 0.6 V
0.2 mA when Vcc < 0.6 V
double
hiccup
B2
Q
&
Q
S
R
turn off
CC
V
UVLO
CC
is shorted to GND.
+
+
-
-
9.1 V
driver:
+500 mA
/ -800 mA
20V
12.6/
5.8 V
6
5
8
V
Drv
HV
CC