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PDF NCP1237 Data sheet ( Hoja de datos )
| Número de pieza | NCP1237 | |
| Descripción | Fixed Frequency Current Mode Controller | |
| Fabricantes | ON Semiconductor | |
| Logotipo |  |
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NCP1237
www.DataSheet4U.com
Fixed Frequency Current
Mode Controller for Flyback
Converters
The NCP1237 is a new generation of the NCP12xx fixed−frequency
current−mode controllers featuring Dynamic Self−Supply (DSS),
pin−to−pin compatible with the previous generation.
The DSS function greatly simplifies the design of the auxiliary supply
and the VCC capacitor by activating the internal startup current source to
supply the controller during transients.
Due to its proprietary Soft−Skip™ mode combined with frequency
foldback, the controller exhibits excellent efficiency in light load
condition while still achieving very low standby power consumption.
This Soft−Skip feature also dramatically reduces the risk of acoustic
noise, which enables the use of inexpensive transformers and
capacitors in the clamping network.
The NCP1237 features a dual−level timer−based fault detection that
controls the amount of transient peak power that the controller can
deliver for a limited time.
Internal frequency jittering, ramp compensation, and a versatile
latch input make this controller an excellent candidate for converters
where ruggedness and components cost are the key constraints.
In addition, the controller includes a new high voltage circuitry that
combines a startup current source and a brown−out / line OVP detector
able to sense the input voltage either from the rectified ac line or the dc
filtered bulk voltage.
Finally, due to a careful design, the precision of critical parameters
is well controlled over the entire temperature range (−40°C to
+125°C), enabling easier design and increased safety (e.g. ±5% for the
peak current limit, ±7% for the oscillator).
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MARKING
DIAGRAM
SOIC−7
CASE 751U
8
37Xff
ALYWX
G
1
37Xff = Specific Device Code
X = A or B
ff = 65, 00, or 33
A = Assembly Location
L = Wafer Lot
Y = Year
W = Work Week
G = Pb−Free Package
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 32 of this data sheet.
Features
• Timer−Based Transient Power and Overload
Protections with Auto−Recovery (Option B) or Latched
(Option A) Operation
• High−Voltage Current Source with DSS with Built−in
Brown−out and Line Overvoltage Protections
• Fixed−Frequency Current−Mode Operation with
Built−in Ramp Compensation
• Frequency Jittering for a Reduced EMI Signature
• Adjustable Overpower Compensation
• Latch−off Input for Severe Fault Conditions, with
Direct Connection of an NTC for Overtemperature
Protection (OTP)
• Protection Against Winding Short−Circuit
• Frequency Foldback transitioning into Soft−Skip for
Improved Performance in Standby
• 65 kHz Oscillator (100 kHz and 133 kHz Versions
Available Upon Request)
• VCC Operation up to 28 V
• Increased Precision on Critical Parameters
• ±1.0 A Peak Drive Capability
• 4.0 ms Soft−Start
• Internal Thermal Shutdown with Hysteresis
• These Devices are Pb−Free, Halogen Free/BFR Free
and are RoHS Compliant*
Typical Applications
• ac−dc Adapters for Notebooks, LCD, and Printers
• Offline Battery Chargers
• Consumer Electronic Power Supplies
• Auxiliary/Housekeeping Power Supplies
*For additional information on our Pb−Free strategy and soldering details, please
download the ON Semiconductor Soldering and Mounting Techniques
Reference Manual, SOLDERRM/D.
© Semiconductor Components Industries, LLC, 2010
February, 2010 − Rev. 1
1
Publication Order Number:
NCP1237/D
1 page  
NCP1237
ELECTRICAL CHARACTERISTICS (For typical values TJ = 25°C, for min/max values TJ = −40°C to +125°Cw, wVHwV.D=a1t2a0SVh,eet4U.com
VCC = 11 V unless otherwise noted)
Characteristics
Test Condition
Symbol
Min Typ Max Unit
HIGH VOLTAGE CURRENT SOURCE
Minimum voltage for current source operation
Current flowing out of VCC pin @ VHV = 60 V
Off−state leakage current
SUPPLY
VCC = 0 V
VCC = VCC(on) − 0.5 V
VHV = 500 V
VHV(min)
Istart1
Istart2
Istart(off)
− − 60
0.2 0.5 0.8
4 8 12
− 25 50
V
mA
mA
Turn−on threshold level, VCC going up
HV current source stop threshold
VCC(on)
11.0 12.0 13.0
V
HV current source restart threshold
Turn−off threshold level
Blanking duration on VCC(min) and VCC(off) detection
VCC decreasing level at which the internal logic resets
VCC level for ISTART1 to ISTART2 transition
Internal current consumption (Note 6)
Guaranteed by design
DRV open, VFB = 3 V
VCC(min)
9.5 10.5 11.5
VCC(off)
8.5 9.5 10.5
tUVLO(blank)
7
10 13
VCC(reset) 4.0 5.2 6.5
VCC(inhibit)
0.4 0.65 0.9
ICC1
2.0 2.5 3.0
V
V
ms
V
V
mA
Cdrv = 1 nF, VFB = 3 V
ICC2
2.3 3.3 4.3
Off mode (skip or before
startup)
Fault mode (fault or latch)
ICC3
ICC4
0.9 1.2 1.5
0.4 0.7 1.0
BROWN−OUT AND LINE OVERVOLTAGE
Brown−out threshold voltage
Timer duration for line cycle drop−out
Overvoltage threshold
Blanking duration on line overvoltage detection
OSCILLATOR
VHV going up
VHV going down
VHV going up
VHV going down
VHV(start)
VHV(stop)
tHV
VHV(OV1)
VHV(OV2)
tOV(blank)
104 112 120
97 105 113
43 61 79
400 430 460
395 425 455
− 250 −
V
ms
V
ms
Oscillator frequency
Maximum duty ratio
Frequency jittering amplitude, in percentage of FOSC
Frequency jittering modulation frequency
OUTPUT DRIVER
Guaranteed by design
Guaranteed by design
fOSC
DMAX
Ajitter
Fjitter
60 65 70
75 80 85
$4 $6 $8
85 125 165
kHz
%
%
Hz
Rise time, 10% to 90% of VCC
Fall time, 90% to 10% of VCC
Current capability
Clamping voltage (maximum gate voltage)
VCC = VCC(min) + 0.2 V,
CDRV = 1 nF
trise − 22 34
VCC = VCC(min) + 0.2 V,
CDRV = 1 nF
tfall − 22 34
VCC = VCC(min) + 0.2 V,
CDRV = 1 nF
DRV high, VDRV = 0 V
DRV low, VDRV = VCC
IDRV(source)
IDRV(sink)
− 1000
− 1000
−
−
VCC = VCCmax – 0.2 V, DRV VDRV(clamp) 11 13.5 16
high
ns
ns
mA
V
High−state voltage drop
VCC = VCC(min) + 0.2 V,
VDRV(drop)
−
−
1
RDRV = 33 kW, DRV high
6. Internal supply current only, current in FB pin not included (current flowing through GND pin only).
V
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5
5 Page 
NCP1237
At startup, the current source turns on when the voltage on
the HV pin is higher than VHV(min), and turns off when VCC
reaches VCC(on). It turns on again when VCC reaches
VCC(min). This sequence repeats until the input voltage is
high enough to ensure a proper startup, i.e. when VHV
reaches VHV(start). The switching actually starts the next
time VCC reaches VCC(on), as shown in Figure 5.
Even though the DSS is able to maintain the VCC voltage
between VCC(on) and VCC(min) by turning the HV startup
VHV
current source on and off, it can onlwy wbwe .uDsaetdaiSnheliegth4tUl.ocaodm
conditions, otherwise the power dissipation on the die would
be too high. As a result, an auxiliary voltage source is needed
to supply VCC during normal operation.
The DSS is useful to keep the controller alive when no
switching pulses are delivered, e.g. in a brown−out
condition, or to prevent the controller from stopping during
load transients when the VCC might drop below VCC(off).
VHV(start)
VHV(min)
VCC
VCC(on)
VCC(min)
VCC(inhibit)
DRV
HV
current
source =
Istart1
Waits
next
VCC(on)
before
starting
time
HV
current
source =
Istart2
time
Figure 5. Startup Timing Diagram
time
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| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet NCP1237.PDF ] | |
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