NCP1236AD100R2G ON Semiconductor, NCP1236AD100R2G Datasheet - Page 19

• Manufacturer Part Number: NCP1236AD100R2G
• Description: IC CTLR CURR MODE 100KHZ 7-SOIC
• Manufacturer: ON Semiconductor

Specifications of NCP1236AD100R2G

• Input Voltage: 28V
• No. Of Outputs: 1
• Voltage Regulator Case Style: SOIC
• No. Of Pins: 8
• Operating Temperature Range: -40°C To +125°C
• Svhc: No SVHC (20-Jun-2011)
• Base Number: 1236
• Rohs Compliant: Yes
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Current sensing
the FB voltage sets the peak current flowing in the
inductance and the MOSFET. This is done through a PWM
comparator: the current is sensed across a resistor and the
resulting voltage is applied to the CS pin. It is applied to one
off and starts – or restarts – when V
soft−start is applied: the current sense setpoint is linearly
increased from 0 (the minimum level can be higher than 0
because of the LEB and propagation delay) until it reaches
V
ILIM
NCP1236 is a current−mode controller, which means that
Each time the controller is starting, i.e. the controller was
FB
CS
(after a duration of t
V
FB(ref)
CURRENT−MODE CONTROL WITH OVERPOWER COMPENSATION AND SOFT−START
R
FB(up)
blanking
blanking
t
t
LEB
BCS
K
FB
SSTART
+
), or until the FB loop
CC
+
−
Soft−start ramp
t
SSTART
Figure 36. Current Sense Block Schematic
V
reaches V
PWM
+
−
CS(stop)
+
−
Soft−start
+
UVLO
Reset
Start
Fault
V
+
−
ILIM
CC(on)
http://onsemi.com
IC Start
IC Stop
, a
19
Protection
input of the PWM comparator through a 250 ns LEB block.
On the other input the FB voltage divided by 5 sets the
threshold: when the voltage ramp reaches this threshold, the
output driver is turned off.
is set by a dedicated comparator.
imposes a setpoint lower than the one imposed by the
soft−start (the 2 comparators outputs are OR’ed). The
soft−start ramp signal is generated by the D/A converter in
the NCP1236, that’s why there are observable 15 discrete
steps instead the truly linearly increasing current setpoint
ramp.
Mode
The maximum value for the current sense is 0.7 V, and it
IC stop
DCMAX
Oscillator
HV stop
Jitter
S
R
Q
Latch
TSD
DRV Stage