NCP1215
Low Cost Variable OFF Time
Switched Mode Power
Supply Controller
The NCP1215 is a controller for low power off−line flyback
Switchemode Power Supplies (SMPS) featuring low size, weight and
cost constraints together with a good low standby power performance.
The operating principle uses switching frequency reduction at light
load by increasing the OFF Time. Also, when OFF Time expands, the
peak current is gradually reduced down to approximately 1/4 of the
maximum peak current to prevent from exciting the transformer
mechanical resonances. The risk of acoustic noise is thus greatly
diminished while keeping good standby power performance.
A low power internal supply block also ensures very low current
consumption at startup without hampering the standby power
performance.
A special primary current sensing technique minimizes the impact
of SMPS switching on control IC operation. The choice of peak
voltage across the current sense resistor allows dissipation to be
further reduced. The negative current sensing technique offers
advantages over a traditional approach by avoiding the voltage drop
incurred by traditional MOSFET source sensing. Thus, the IC drive
capability is greatly improved.
Finally, the bulk input ripple ensures a natural frequency dithering
which smooths the EMI signature.
Features
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MARKING
DIAGRAMS
8
8
1
SOIC−8
D SUFFIX
CASE 751
1
6
TSOP−6
(SOT23−6, SC59−6)
SN SUFFIX
CASE 318G
1
FAA
A
L
Y
W
P1215
ALYW
6
1
FAAYW
= Specific Device Code
= Assembly Location
= Wafer Lot
= Year
= Work Week
PIN CONNECTIONS
SOIC−8
FB 1
CT 2
CS 3
GND
4
(Top View)
TSOP−6
CS
GND
1
2
3
(Top View)
6
5
4
Gate
V
CC
FB
8
7
6
5
NC
NC
V
CC
Gate
•
•
•
•
•
•
•
•
•
•
•
•
Pb−Free Package is Available
Variable OFF Time Control Method
Very Low Current Consumption at Startup
Natural Frequency Dithering for Improved EMI Signature
Current Mode Control Operation
Peak Current Compression Reduces Transformer Noise
Programmable Current Sense Resistor Peak Voltage
Undervoltage Lockout
Typical Applications
CT
Auxiliary Power Supply
Standby Power Supply
AC−DC Adapter
Off−line Battery Charger
ORDERING INFORMATION
Device
NCP1215DR2
NCP1215DR2G
NCP1215SNT1
Package
SOIC−8
SOIC−8
(Pb−Free)
TSOP−6
Shipping
†
2500 Tape & Reel
2500 Tape & Reel
3000 Tape & Reel
†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, 2005
1
July, 2005 − Rev. 3
Publication Order Number:
NCP1215/D
NCP1215
Line
+
+
+
FB
CT
CS
N
NC
NC
Vcc
−
+
GND Gate *
* If your application requires a gate−source resistor, please refer to design guidelines in this document.
Figure 1. Typical Application
FB
Feedback Loop
Control
V
DD
I
ref
Off−Time
Comparator
Reference
Regulator
−
Voffset
+
CT
10
mA
0−7 V
−
+
+
−
V
CC
12/8.5 V
Undervoltage
Lockout
CS
12.5−50
mA
Set
Q
Gate Driver
Gate
Current Sense Comparator
GND
+
−
Reset
Q
Figure 2. Representative Block Diagram
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2
NCP1215
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PIN FUNCTION DESCRIPTION
TSOP−6
4
3
1
2
6
5
7
8
SOIC−8
1
2
3
4
5
6
7
8
Symbol
FB
Description
The FB pin provides voltage feedback loop. The current injected into the pin determines the
primary switch OFF time interval. It also influences the peak value of the primary current.
Connection for an external timing programming capacitor.
The CS pin senses the power switch current.
Primary and internal ground.
Output drive for an external power MOSFET.
Power supply voltage and Undervoltage Lockout.
Unconnected pin.
Unconnected pin.
CT
CS
GND
Gate
Vcc
NC
NC
MAXIMUM RATINGS
Rating
Symbol
V
cc
Value
18
Unit
V
V
V
Power Supply Voltage
FB Pins Voltage Range
V
FB
V
in
−0.3 to 18
−0.3 to 10
178
150
CS and CT Pin Voltage Range
Thermal Resistance, Junction−to−Air (SOIC−8 Version)
Junction Temperature
Storage Temperature Range
ESD Voltage Protection, Human Body Model (Except CT Pin)
ESD Voltage Protection, Human Body Model for CT Pin
ESD Voltage Protection, Machine Model (Except CT Pin)
ESD Voltage Protection, Machine Model for CT Pin
R
qJA
T
J
T
stg
V
ESD−HBM
V
ESD−HBM−CT
V
ESD−MM
V
ESD−MM−CT
°C/W
°C
°C
kV
kV
V
V
−60 to +150
2.0
1.5
200
150
Maximum ratings are those values beyond which device damage can occur. Maximum ratings applied to the device are individual stress limit
values (not normal operating conditions) and are not valid simultaneously. If these limits are exceeded, device functional operation is not implied,
damage may occur and reliability may be affected.
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3
NCP1215
ELECTRICAL CHARACTERISTICS
(V
CC
= 12 V, for typical values T
j
= 25°C, for min/max values T
j
= 0°C to +105°C, unless
otherwise noted.)
Characteristic
VOLTAGE FEEDBACK
Offset Voltage
Maximum CT Pin Voltage at FB Current = 25
mA
(Including V
offset
)
Maximum CT Pin Voltage at FB Current = 50
mA
(Including V
offset
)
CT PIN − OFF TIME CONTROL
Source Current (CT Pin Grounded)
Source Current Maximum Voltage Capability
Minimum CT Pin Voltage (Pin Unloaded, Discharge Switch Turned On)
CURRENT SENSE
Minimum Source Current (I
FB
= 180
mA,
CT Pin Grounded)
Maximum Source Current (I
FB
= 0
mA,
CT Pin Grounded)
Comparator Threshold Voltage
Propagation Delay (CS Falling Edge to Gate Output)
GATE DRIVE
Sink Resistance (I
sink
= 30 mA)
Source Resistance (I
source
= 30 mA)
POWER SUPPLY
V
CC
Startup Voltage
Undervoltage Lockout Threshold Voltage
Hysteresis (V
startup
− V
UVLO
)
V
CC
Startup Current Consumption (V
CC
= 8.0 V)
V
CC
Steady State Current Consumption
(C
GATE
= 1.0 nF, f
SW
= 100 kHz, FB open)
V
startup
V
UVLO
V
hys
I
CC−start
I
CC−SW
−
7.2
2.2
−
0.55
12.5
9.0
3.5
2.8
0.9
14.2
−
−
6.5
1.75
V
V
V
mA
mA
R
OL
R
OH
25
60
40
80
90
130
W
W
I
CS−min
I
CS−max
V
th
t
delay
8.0
40
15
−
12.5
49
42
215
16
58
80
310
mA
mA
mV
ns
I
CT
V
CT−max
V
CT−min
8.0
−
−
9.8
6.5
−
11.5
−
20
mA
V
mV
V
offset
V
CT−25mA
V
CT−50mA
1.05
2.4
3.6
1.19
3.1
4.6
1.34
4.3
6.2
V
V
V
Symbol
Min
Typ
Max
Unit
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4
NCP1215
TYPICAL CHARACTERISTICS
11.6
11.5
11.4
11.3
11.2
11.1
11.0
−25
V
UVLO
, (V)
0
25
50
75
100
125
8.8
8.7
8.6
8.5
8.4
8.3
8.2
−25
V
startup
, (V)
0
25
50
75
100
125
T
J
, JUNCTION TEMPERATURE (°C)
T
J
, JUNCTION TEMPERATURE (°C)
Figure 3. V
startup
Threshold vs. Junction
Temperature
0.990
0.985
I
CC−SW
, (mA)
0.980
0.975
V
offset
, (V)
1.20
1.18
1.16
1.14
1.12
1.10
1.08
1.06
1.04
1.02
0.960
−25
0
25
50
75
100
125
1.00
−25
Figure 4. V
UVLO
Threshold vs. Junction
Temperature
0.970
0.965
0
25
50
75
100
125
T
J
, JUNCTION TEMPERATURE (°C)
T
J
, JUNCTION TEMPERATURE (°C)
Figure 5. Operating Current Consumption vs.
Junction Temperature
Figure 6. Offset Voltage vs. Junction
Temperature
49.0
48.5
48.0
I
CS−max
, (mA)
47.5
47.0
46.5
46.0
45.5
−25
0
25
50
75
100
125
V
CS−th
, (mV)
65
60
55
50
45
40
35
30
−25
0
25
50
75
100
125
T
J
, JUNCTION TEMPERATURE (°C)
T
J
, JUNCTION TEMPERATURE (°C)
Figure 7. Current Sense Source Current vs.
Junction Temperature
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5
Figure 8. Current Sense Threshold vs.
Junction Temperature
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