NCP1235
Product Preview
Fixed Frequency Current
Mode Controller for Flyback
Converters
The NCP1235 is a new fixed−frequency current−mode controller
featuring Dynamic Self−Supply (DSS). This device is pin−to−pin
compatible with the previous NCP12xx families.
The DSS 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 transients.
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 converters where components cost is the key
constraints.
In addition, the controller includes a new high voltage circuitry that
combines a start−up current source and a brown−out detector able to
sense the input voltage either from the rectified ac line or the dc
filtered bulk voltage. The high voltage sensing circuitry is used for the
overpower protection purposes as well. Overpower protection,
overload protection, and next protective features increases safety level
of the final application.
Finally, due to a careful design, the precision of critical parameters
is well controlled over the entire temperature range (−40°C to
+125°C).
Features
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MARKING
DIAGRAM
8
35A065
ALYWX
G
1
SOIC−7
CASE 751U
35A065 = Specific Device Code
A
= Assembly Location
L
= Wafer Lot
Y
= Year
W
= Work Week
G
= Pb−Free Package
PIN CONNECTIONS
Latch 1
FB 2
CS 3
GND
4
(Top View)
6
5
V
CC
DRV
8
HV
•
Fixed−Frequency Current−Mode Operation with Built−In Ramp
•
•
•
•
•
•
•
ORDERING INFORMATION
Compensation
See detailed ordering and shipping information in the package
65 kHz Oscillator Frequency
dimensions section on page 33 of this data sheet.
Frequency Foldback then Skip Mode for Maximized Performance in
Light Load and Standby Conditions
Timer−Based Overload Protection then Device is Latched
High−voltage Current Source with Brown−Out
•
Internal Thermal Shutdown
detection and Dynamic Self−Supply, Simplifying the
•
Pin−to−Pin Compatible with the Existing NCP12xx
Design of the V
CC
Capacitor
Series
Frequency Modulation for Softened EMI Signature,
•
These Devices are Pb−Free, Halogen Free/BFR Free
including during Frequency Foldback mode
and are RoHS Compliant
Adjustable Overpower Compensation
Typical Applications
Latch−off Input for Severe Fault Conditions, Allowing
•
AC−DC Adapters for Notebooks, LCD, and Printers
Direct Connection of an NTC for Overtemperature
•
Offline Battery Chargers
Protection (OTP)
•
Consumer Electronic Power Supplies
V
CC
Operation up to 28 V, with Overvoltage Detection
•
Auxiliary/Housekeeping Power Supplies
$500
mA Peak Source / Sink Current Drive Capability
•
•
•
4.0 ms Soft−Start
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, 2015
1
January, 2015 − Rev. P0
Publication Order Number:
NCP1235/D
NCP1235
TYPICAL APPLICATION EXAMPLE
VIN
(dc)
VOUT
LATCH
FB
CS
GND
NCP1236
HV
VCC
DRV
Figure 1. Flyback Converter Application Using the NCP1235
OPTIONS
Part
NCP1235
Option
A
Frequency
65 kHz
OCP Fault
Latched
Fault Timer
128 ms
Autorecovery
Timer
16 ms
PIN FUNCTION DESCRIPTION
Pin No
1
2
3
4
5
6
Pin Name
LATCH
FB
CS
GND
DRV
V
CC
Drive output
V
CC
input
Function
Latch−Off Input
Feedback
Current Sense
Pin Description
Pull the pin up or down to latch−off 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.
This Input senses the Primary Current for current−mode operation, and Offers
an overpower compensation adjustment.
IC Ground
Drives external MOSFET
This supply pin accepts up to 28 Vdc, with overvoltage detection
8
HV
High−voltage pin
Connects to the bulk capacitor or the rectified AC line to perform the functions
of Start−up Current Source, Dynamic Self−Supply and brown−out detection
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2
NCP1235
SIMPLIFIED INTERNAL BLOCK SCHEMATIC
−
+
HV
Dual HV
start−up
current source
V
CC
V
FB(ref)
+
20 kW
/5
slope
comp.
V
skip
−
+
Jitter
Clamp
S
Q
R
+
−
V
ILIM
I
LIMIT
IC stop
GND
I
LIMIT
D
MAX
+
Fault Flag
+
−
V
CS(stop)
timer
PWM
t
fault
timer
Fault
Brown−out
Reset
t
autorec
UVLO
Protection
Mode
release
Brown−out
For
Autorecovery
protection
mode only
Latch
TSD
DRV
Brown−out
+
−
V
OVP
blanking
t
Latch(OVP)
HV sample
V
CC
OVP
HV dc
BO
V
DD
I
NTC
I
NTC
+
Latch
+
1 kW
−
+
V
OTP
blanking
t
Latch(OTP)
S
Q
R
Soft−start
end
Brown−out
Reset
Latch
TSD
TSD
V
clamp
Reset
UVLO
VDD
IC Start
VCC OVP
TSD HV current
Reset
UVLO
V
CC
V
DD
management
Start
OVP
FB
HV sample
+
−
PWM
V to I
I
OPC
= 0.5m x
(V
HV
− 125)
Soft−start
+
−
+
Sawtooth
Stop
Foldback
V
FB(OPC)
CS
+
blanking
t
BCS
S
Q
R
−
+
Oscillator
Soft−start ramp Start
t
End
SSTART
Reset
IC Start
IC Stop
DMAX
DCMAX
blanking
t
LEB
Soft−start end
Figure 2. Simplified Internal Block Schematic
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3
NCP1235
MAXIMUM RATINGS
Rating
Supply Pin (pin 6) (Note 2)
Voltage range
Current range
High Voltage Pin (pin 8) (Note 2)
Voltage range
Current range
Driver Pin (pin 5) (Note 2)
Voltage range
Current range
All other pins (Note 2)
Voltage range
Current range
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)
Temperature Range
Operating Junction Temperature
Storage Temperature Range
ESD Capability (Note 1)
Human Body Model (All pins except HV)
Machine Model
Symbol
V
CCMAX
I
CCMAX
V
HVMAX
I
HVMAX
V
DRVMAX
I
DRVMAX
V
MAX
I
MAX
R
θJ−A
Value
–0.3 to 28
$30
–0.3 to 500
$20
–0.3 to 20
$1000
–0.3 to 10
$10
162
147
115
°C
T
JMAX
T
STRGMAX
−40 to +150
−60 to +150
V
2000
200
Unit
V
mA
V
mA
V
mA
V
mA
°C/W
Stresses exceeding those listed in the Maximum Ratings table may damage the device. If any of these limits are exceeded, device functionality
should not be assumed, damage may occur and reliability may be affected.
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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4
NCP1235
ELECTRICAL CHARACTERISTICS
(For typical values T
J
= 25°C, for min/max values T
J
= −40°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
Off−state leakage current
SUPPLY
Turn−on threshold level, V
CC
going up
HV current source stop threshold
HV current source restart threshold
Turn−off threshold
Overvoltage threshold
Blanking duration on V
CC(off)
and
V
CC(ovp)
detection (Note 7)
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
C
drv
= 1 nF, V
FB
= 3 V,
Off mode (skip or before start−up)
Fault mode (fault or latch)
V
CC(on)
11.0
12.0
13.0
V
V
CC
= 0 V
V
CC
= V
CC(on)
− 0.5 V
V
HV
= 500 V
V
HV(min)
I
start1
I
start2
I
start(off)
−
0.2
3
−
30
0.5
6
25
60
0.8
9
50
V
mA
mA
Test Condition
Symbol
Min
Typ
Max
Unit
V
CC(min)
V
CC(off)
V
CC(ovp)
t
VCC(blank)
V
CC(reset)
V
CC(inhibit)
I
CC1
I
CC2
I
CC3
I
CC4
9.5
8.5
25
7
3.6
0.4
1.2
1.9
0.67
0.4
10.5
9.5
26.5
10
5.0
1.0
1.8
2.5
0.9
0.7
11.5
10.5
28
13
6.0
1.6
2.2
3.2
1.13
1.0
V
V
V
ms
V
V
mA
BROWN−OUT
Brown−Out thresholds
Timer duration for line cycle
drop−out
OSCILLATOR
Oscillator frequency
Maximum duty cycle
Frequency jittering amplitude, in
percentage of F
OSC
Frequency jittering modulation
frequency
OUTPUT DRIVER
Rise time, 10% to 90 % of V
CC
Fall time, 90% to 10 % of V
CC
Current capability
V
CC
= V
CC(min)
+ 0.2 V, C
DRV
= 1 nF
V
CC
= V
CC(min)
+ 0.2 V, C
DRV
= 1 nF
V
CC
= V
CC(min)
+ 0.2 V, C
DRV
= 1 nF
DRV high, V
DRV
= 0 V
DRV low, V
DRV
= V
CC
V
CC
= V
CCmax
– 0.2 V, DRV high, R
DRV
= 33 kW, C
load
= 220 pF
V
CC
= V
CC(min)
+ 0.2 V, R
DRV
= 33 kW,
DRV high
t
rise
t
fall
I
DRV(source)
I
DRV(sink)
V
DRV(clamp)
V
DRV(drop)
−
−
−
−
11
−
40
40
500
500
13.5
−
70
70
−
−
16
1
ns
ns
mA
V
V
f
OSC
D
MAX
A
jitter
F
jitter
60
92
75
−
85
65
100
80
±10
125
70
108
85
−
165
kHz
%
%
Hz
V
HV
going up
V
HV
going down
V
HV(start)
V
HV(stop)
t
HV
92
79
47
107
92
68
122
105
90
V
ms
Clamping voltage (maximum
gate voltage)
High−state voltage drop
6. Internal supply current only, current in FB pin not included (current flowing in GND pin only).
7. Guaranteed by design.
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