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NCP1212
Current Mode PWM
Controller for Both Forward
and Flyback Converters
NCP1212 is a high performance current mode PWM controller
specifically designed for off-
-line and DC- -DC converter
-to-
applications. The device requires very few external components and
offers designer additional protection for better system reliability. The
device features a trimmed oscillator for precise Duty Cycle control,
accurate bandgap voltage reference, high gain error amplifier, current
sensing comparator and a high current totem pole output gate driver
that ideally drives the external power MOSFET. Additionally, the
device has built- programmable Brownout Detect and Soft-
-in
-Start
features to enhance system reliability. Also, the 48%/82% selectable
maximum turn on Duty Cycle control and external programmable
switching frequency capabilities make this device an ideal controller
for both forward and flyback configurations. This device is available
in both PDIP- and space saving SOIC- packages.
-8
-8
Features
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MARKING
DIAGRAM
8
8
1
SOIC-
-8
DSUFFIX
CASE 751
1
N1212
ALYW
G
8
PDIP-
-8
N SUFFIX
CASE 626
1
A
L, WL
Y, YY
W, WW
G
G
1
NCP1212
AWL
YYWWG
Trimmed Oscillator Charge and Discharge Current for Precise Duty
Cycle Control
Internal High Accuracy Bandgap Voltage Reference
Current Mode Operation up to 200 kHz
Inherent Feed Forward Compensation
Latching PWM for Cycle- -Cycle Current Limiting
-by-
High Current Totem Pole Output Gate Driver
Low Startup and Operating Current
Internal Undervoltage Lockout with Hysteresis
Internal Leading Edge Blanking for Current Feedback
Direct Interface with Optocoupler for Secondary Sensing
Built- Soft-
-in
-Start Function, Programmable by External Capacitor
User Programmable 48%/82% Maximum Duty Cycle Selection
Output Overvoltage Protection Against Open Loop
AC Line Brownout Detect Protection
Output Overload Protection Irrespective of Auxiliary Voltage Level
These are Pb-
-Free Devices
ATX PC Power Supply
Universal Input Wall Mount Adaptors
CRT Monitor
All Flyback and Forward SMPS Systems
8
= Assembly Location
= Wafer Lot
= Year
= Work Week
= Pb--Free Package
= Pb--Free Package
PIN CONNECTIONS
FB
BOK
CS
CT
1
2
3
4
(Top View)
8
7
6
5
SS/DMAX
VCC
DRV
GND
ORDERING INFORMATION
Device
NCP1212DR2G
Package
SOIC--8
(Pb--Free)
PDIP--8
(Pb--Free)
Shipping
†
2500/Tape & Reel
Typical Applications
NCP1212PG
50 Units / Rail
†For information on tape and reel specifications,
including part orientation and tape sizes, please
refer to our Tape and Reel Packaging Specifications
Brochure, BRD8011/D.
Semiconductor Components Industries, LLC, 2010
December, 2010 - Rev. 5
-
1
Publication Order Number:
NCP1212/D
F1
FUSE
T3
BR1
1
3
4
+
2
C1
470
mf/400
V
R2
3.3 K
Rsense
0.22/2 W
Q1
3
R1
576 K
C2
10 nf/1 kv
D2
MBR3045
R3
36 K
D1
MUR180
RFI FILTER
5V
2
AC Input
+
--
X2 Cap
1
X2 Cap
+
C7
3300
mf/
10 V
0
GND
Form Standby SMPS
Auxiliary Winding
IC1
NCP1212
FB
BOK
CS
CT
C4
1 nf
GND
DRV
C3
0.1
mf
C5
0.1
mf
4
VCC
SS/DMAX
NCP1212
Figure 1. Typical Application Circuit
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2
R6
220
PC817
1
2
IC2
3
U1
TL431
C6
R5
100 0.1
mf
R8
300
+5 V
9K
--
+5 V
8
mA
3R
28
mA
--
SS/DMAX
↓
--
+
Overload
Shutdown
+
FB
R
--
OVLO
(25 V)
UVLO
(10 V)
300 ns
LEB
Current Limit
--
+
+
--
Brownout
Detection
1V
5V
+5 V
45
mA
↓
--
+
--
+
+
0.5 V
↓
+
VCC
Vref
Regulator
--
+
CS
+
--
15 V
NCP1212
Figure 2. Simplified Functional Block Diagram
--
CLK
+
1.21 V
D
CLK
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SW2
--
+
S
Q
D
Q
OSC
Clock
+
--
IMAX
Max. Duty
Cycle
48% or 82%
+
--
--
+
S
Q
Q
Reset
Overload
Enable
3.2 V
3
BOK
F/F
R
Q
Totem Pole Drive
S
Q
DRV
CT
GND
NCP1212
PIN FUNCTION DESCRIPTION
Pin
1
2
Name
FB
BOK
Function
Feedback Input
Brownout Detect
with Hysteresis
Description
This pin detects voltage feedback from output, can be connected directly to the
optocoupler collector pin.
This is the inverting input of the brownout detect comparator. The brownout detect
comparator has a detect threshold voltage of 1.21 V. This pin senses the voltage of the
bulk capacitor through a resistor divider network to determine the brownout event. The
hysteresis band is provided by a 45
mA
current flows out of this pin to the resistor
network.
During output on–time of the power switch, this pin receives a voltage proportional to
power switch current set by the current sensing resistor. The information is utilized to
terminate output switch conduction by PWM action or overcurrent limit circuitry.
Connecting a capacitor from CT pin to ground programs the internal oscillator frequency.
The oscillator can operate up to 200 kHz.
--
This is a high current totem pole output. The PWM driving control is provided by this pin.
The current and slew rate capability of this pin are suitable to drive a Power MOSFET.
This pin is the positive supply of the IC. The driver output gets disabled when the voltage
becomes higher than 25 V and the operating range is between 10 V and 25 V. The
startup voltage is set at 15 V.
This is a multi--function pin. Soft--start effect is provided during startup with a capacitor
connected to this pin. After soft--start period elapsed, the capacitor is used for timing
control to determine output overload. If only a capacitor is connected to this pin, its final
voltage is
~4.3
V and maximum turn--on duty cycle DMAX is set at 82%. Connect a
resistor in parallel with the capacitor can alter the final voltage of this pin. 48% DMAX is
selected if this pin stays at 2.1 V to 2.8 V after soft--start period.
3
CS
Current Sense Input
4
5
6
7
CT
GND
DRV
VCC
Programmed Oscillator
Frequency
IC Ground
Gate Driver Output
Positive Supply to IC
8
SS/DMAX
Soft--Start Time
Programming and
Maximum Duty Cycle
Selection
MAXIMUM RATINGS
(T
J
= 25C unless otherwise noted.)
Rating
Power Supply Voltage (Pin 7)
Input/Output Pins (Pins 1, 2, 3, 4, 8)
Gate Driver Output Pin (Pin 6)
Power Dissipation and Thermal Characteristics
Thermal Resistance, Junction--to--Air, PDIP--8 Version
Thermal Resistance, Junction--to--Air, SOIC--8 Version
Output Current, Source or Sink
Operating Junction Temperature Range
Operating Ambient Temperature Range
Storage Temperature Range
ESD Capability, HBM (All pins except V
CC
pin) (Note 1)
ESD Capability, Machine Model (All pins except V
CC
pin) (Note 1)
Symbol
V
CC
V
IO
V
DRV
R
θJ--A
Value
--0.3, 28
--0.3, 6.5
--0.3, 14
100
178
1.0
--40 to +150
--25 to +105
--55 to +150
2.0
200
Unit
V
V
V
C/W
I
DRV
T
J
T
A
T
stg
--
--
A
C
C
C
kV
V
Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the
Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect
device reliability.
1. This device series contains ESD protection and exceeds the following tests:
Human Body Model (HBM)
≤2.0
kV per JEDEC standard: JESD22--A114.
Machine Model (MM)
≤200
V per JEDEC standard: JESD22--A115.
2. Latchup Current Maximum Rating:
150
mA per JEDEC standard: JESD78.
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