NCP1246
Product Preview
Fixed Frequency Current
Mode Controller for Flyback
Converters
The NCP1246 is a new fixedïfrequency currentïmode controller
featuring the Dynamic SelfïSupply. This function greatly simplifies
the design of the auxiliary supply and the V
CC
capacitor by activating
the internal startup current source to supply the controller during
startïup, transients, latch, standïby etc. This device contains a special
HV detector which detect the application unplug from the AC input
line and triggers the X2 discharge current. This HV structure allows
the brownïout detection as well.
It features a timerïbased fault detection that ensures the detection of
overload and an adjustable compensation to help keep the maximum
power independent of the input voltage.
Due to frequency foldback, the controller exhibits excellent
efficiency in light load condition while still achieving very low
standby power consumption. Internal frequency jittering, ramp
compensation, and a versatile latch input make this controller an
excellent candidate for the robust power supply designs.
A dedicated Off mode allows to reach the extremely low no load
input power consumption via “sleeping” whole device and thus
minimize the power consumption of the control circuitry.
Features
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MARKING
DIAGRAM
8
46Xff
ALYWX
G
1
SOICï7
CASE 751U
46Xff = Specific Device Code
X = A or B
ff = 65 or 100
A
= Assembly Location
L
= Wafer Lot
Y
= Year
W
= Work Week
G
= PbïFree Package
PIN CONNECTIONS
Latch 1
FB 2
CS 3
6
V
CC
8
HV
•
FixedïFrequency CurrentïMode Operation (65 kHz and 100 kHz
•
•
•
•
•
•
•
•
•
•
frequency options)
GND 4
5 DRV
Frequency Foldback then Skip Mode for Maximized Performance in
(Top View)
Light Load and Standby Conditions
TimerïBased Overload Protection with Latched (option A) or
ORDERING INFORMATION
AutoïRecovery (Option B) Operation
See detailed ordering and shipping information in the package
Highïvoltage Current Source with BrownïOut Detection and
dimensions section on page 37 of this data sheet.
Dynamic SelfïSupply, Simplifying the Design of the V
CC
Circuitry
Frequency Modulation for Softened EMI Signature
•
NoïLoad Standby Power < 30 mW
Adjustable Overpower Protection Dependant on the
•
X2 Capacitor in EMI Filter Discharging Feature
Bulk Voltage
•
These are PbïFree Devices
Latchïoff Input Combined with the Overpower
Typical Applications
Protection Sensing Input
•
ACïDC Adapters for Notebooks, LCD, and Printers
V
CC
Operation up to 28 V, With Overvoltage Detection
•
Offline Battery Chargers
500/800 mA Source/Sink Drive Peak Current
•
Consumer Electronic Power Supplies
Capability
•
Auxiliary/Housekeeping Power Supplies
10 ms SoftïStart
•
Offline Adapters for Notebooks
Internal Thermal Shutdown
This document contains information on a product under development. ON Semiconductor
reserves the right to change or discontinue this product without notice.
©
Semiconductor Components Industries, LLC, 2012
1
April, 2012 ï Rev. P0
Publication Order Number:
NCP1246/D
NCP1246
TYPICAL APPLICATION EXAMPLE
Figure 1. Flyback Converter Application Using the NCP1246
PIN FUNCTION DESCRIPTION
Pin No
1
2
3
4
5
6
Pin Name
LATCH
FB
CS
GND
DRV
VCC
Function
LatchïOff Input
Feedback + Shutdown pin
Current Sense
ï
Drive output
VCC input
Pin Description
Pull the pin up or down to latchïoff the controller. An internal current source
allows the direct connection of an NTC for over temperature detection.
An optocoupler collector to ground controls the output regulation. The part
goes to the low consumption Off mode if the FB input pin is pulled to GND.
This Input senses the Primary Current for currentïmode operation, and
offers an overpower compensation adjustment.
The controller ground
Drives external MOSFET
This supply pin accepts up to 28 Vdc, with overvoltage detection. The pin is
connected to an external auxiliary voltage. It is not allowed to connect
another circuit to this pin to keep low input power consumption.
Connects to the rectified AC line to perform the functions of Startïup
Current Source, SelfïSupply, brownïout detection and X2 capacitor
discharge function and the HV sensing for the overpower protection
purposes. It is not allowed to connect this pin to DC voltage.
8
HV
Highïvoltage pin
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2
NCP1246
SIMPLIFIED INTERNAL BLOCK SCHEMATIC
Figure 2. Simplified Internal Block Schematic
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3
NCP1246
MAXIMUM RATINGS
Rating
DRV
(pin 5)
V
CC
(pin 6)
HV
(pin 8)
V
max
R
qJïA
Symbol
Maximum voltage on DRV pin
(DcïCurrent selfïlimited if operated within the allowed range) (Note 2)
V
CC
Power Supply voltage, V
CC
pin, continuous voltage
Power Supply voltage, V
CC
pin, continuous voltage (Note 2)
Maximum voltage on HV pin
(DcïCurrent selfïlimited if operated within the allowed range)
Maximum voltage on low power pins (except pin 5, pin 6 and pin 8)
(DcïCurrent selfïlimited if operated within the allowed range) (Note 2)
Thermal Resistance SOIC-7
Junction-to-Air, low conductivity PCB (Note 3)
Junction-to-Air, medium conductivity PCB (Note 4)
Junction-to-Air, high conductivity PCB (Note 5)
Thermal Resistance JunctionïtoïCase
Operating Junction Temperature
Storage Temperature Range
ESD Capability, HBM model (All pins except HV)
ESD Capability, Machine Model (Note 1)
Value
–0.3 to 20
±1000
(peak)
–0.3 to 28
±30
(peak)
–0.3 to 500
±20
–0.3 to 10
±10
(peak)
162
147
115
73
ï40 to +150
ï60 to +150
> 2000
> 200
°C/W
°C
°C
V
V
Unit
V
mA
V
mA
V
mA
V
mA
°C/W
R
qJïC
T
JMAX
T
STRGMAX
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 2000 V per JEDEC standard JESD22, Method A114E
Machine Model Method 200 V per JEDEC standard JESD22, Method A115A
2. This device contains latch-up protection and exceeds 100 mA per JEDEC Standard JESD78.
3. As mounted on a 80 x 100 x 1.5 mm FR4 substrate with a single layer of 50 mm
2
of 2 oz copper traces and heat spreading area. As specified
for a JEDEC 51-1 conductivity test PCB. Test conditions were under natural convection or zero air flow.
4. As mounted on a 80 x 100 x 1.5 mm FR4 substrate with a single layer of 100 mm
2
of 2 oz copper traces and heat spreading area. As specified
for a JEDEC 51-2 conductivity test PCB. Test conditions were under natural convection or zero air flow.
5. As mounted on a 80 x 100 x 1.5 mm FR4 substrate with a single layer of 650 mm
2
of 2 oz copper traces and heat spreading area. As specified
for a JEDEC 51-3 conductivity test PCB. Test conditions were under natural convection or zero air flow.
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NCP1246
ELECTRICAL CHARACTERISTICS
(For typical values T
J
= 25°C, for min/max values T
J
= ï40°C to +125°C, V
HV
= 125 V,
V
CC
= 11 V unless otherwise noted)
Characteristics
HIGH VOLTAGE CURRENT SOURCE
Minimum voltage for current source
operation
Current flowing out of V
CC
pin
Offïstate leakage current
Offïmode HV supply current
V
CC
= 0 V
V
CC
= V
CC(on)
ï 0.5 V
V
HV
= 500 V, V
CC
= 15 V
V
HV
= 141 V,
V
HV
= 325 V,
V
CC
loaded by 4.7
mF
cap
V
HV(min)
I
start1
I
start2
I
start(off)
I
HV(off)
ï
0.2
5
10
ï
ï
30
0.5
8
25
45
50
40
0.8
11
50
60
70
V
mA
mA
mA
Test Condition
Symbol
Min
Typ
Max
Unit
SUPPLY
HV current source regulation threshold
Turnïon threshold level, V
CC
going up
HV current source stop threshold
HV current source restart threshold
Turnïoff threshold
Overvoltage threshold
Blanking duration on V
CC(off)
and V
CC(ovp)
detection
V
CC
decreasing level at which the internal
logic resets
V
CC
level for I
START1
to I
START2
transition
Internal current consumption (Note 6)
DRV open, V
FB
= 3 V, 65 kHz
DRV open, V
FB
= 3 V, 100 kHz
Cdrv = 1 nF, V
FB
= 3 V, 65 kHz
Cdrv = 1 nF, V
FB
= 3 V, 100 kHz
Off mode (skip or before startïup)
I
CC4
Fault mode (fault or latch)
BROWNïOUT
BrownïOut thresholds
Timer duration for line cycle dropïout
X2 DISCHARGE
Comparator hysteresis observed at HV pin
HV signal sampling period
Timer duration for no line detection
Discharge timer duration
OSCILLATOR
Oscillator frequency
Maximum on time for T
J
= 25°C to +125°C
only
Maximum on time
f
OSC
= 65 kHz
f
OSC
= 100 kHz
f
OSC
= 65 kHz
f
OSC
= 100 kHz
f
OSC
t
ONmax(65kHz)
t
ONmax(100kHz)
t
ONmax(65kHz)
t
ONmax(100kHz)
58
87
11.5
7.5
11.3
7.4
65
100
12.3
8.0
12.3
8.0
72
109
13.1
8.5
13.1
8.5
kHz
ms
ms
V
HV(hyst)
T
sample
t
DET
t
DIS
1.5
ï
21
21
3.5
1.0
32
32
5
ï
43
43
V
ms
ms
ms
V
HV
going up
V
HV
going down
V
HV(start)
V
HV(stop)
t
HV
102
94
43
111
103
ï
120
112
86
V
ms
0.3
0.6
0.9
V
CC(reg)
V
CC(on)
V
CC(min)
V
CC(off)
V
CC(ovp)
t
VCC(blank)
V
CC(reset)
V
CC(inhibit)
I
CC
1
I
CC
1
I
CC
2
I
CC
2
I
CC3
8
11.0
9.5
8.5
25
7
4.8
0.2
1.3
1.3
1.8
2.3
0.67
11
12.0
10.5
8.9
26.5
10
7.0
0.8
1.85
1.85
2.6
2.9
0.9
ï
13.0
11.5
9.3
28
13
7.7
1.25
2.2
2.2
3.0
3.5
1.13
V
V
V
V
V
ms
V
V
mA
6. Internal supply current only, currents sourced via FB pin is not included (current is flowing in GND pin only).
7. Guaranteed by design.
8. CS pin source current is a sum of I
bias
and I
OPC
, thus at V
HV
= 125 V is observed the I
bias
only, because I
OPC
is switched off.
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