ONSEMI NCP1338PG

NCP1338
PWM Current-Mode
Controller for Free Running
Quasi-Resonant Operation
The NCP1338 combines a true current mode modulator and a
demagnetization detector which ensures full Borderline/Critical
Conduction Mode in any load/line conditions together with
minimum drain voltage switching (Quasi-Resonant operation). The
transformer core reset detection is done internally, without using any
external signal, due to the Soxyless concept. The frequency is
internally limited to 130 kHz, preventing the controller from
operating above the 150 kHz CISPR-22 EMI starting limit.
By monitoring the feedback pin activity, the controller enters
ripple mode as soon as the power demand falls below a
predetermined level. As each restart is softened by an internal
Soft-Skipt, and as the frequency cannot go below 25 kHz, no
audible noise can be heard.
The NCP1338 also features an efficient protective circuitry which,
in presence of an overcurrent condition, disables the output pulses
and enters a safe burst mode, trying to restart. Once the default has
gone, the device auto-recovers. Also included is a bulk voltage
monitoring function (known as brown-out protection), an adjustable
overpower compensation, and a VCC OVP. Finally, an internal 4.0 ms
Soft-Skip eliminates the traditional startup stress. NCP1338 can be
used in applications where the VCC supply voltage is delivered by an
external dc voltage source.
Features
•Free-Running Borderline/Critical Mode Quasi-Resonant Operation
•Current-Mode
•Soft-Skip Mode with Minimum Switching Frequency for Standby
•Auto-Recovery Short-Circuit Protection Independent of Auxiliary
Voltage
•Overvoltage Protection
•Brown-Out Protection
•Two Externally Triggerable Fault Comparators (one for a disable
function, and the other for a permanent latch)
•Internal 4.0 ms Soft-Skip
•500 mA Peak Current Drive Sink Capability
•130 kHz Max Frequency
•Internal Leading Edge Blanking
•Internal Temperature Shutdown
•Direct Optocoupler Connection
•Dynamic Self-Supply with Levels of 12 V (On) and 10 V (Off)
•SPICE Models Available for TRANsient and AC Analysis
•These are Pb-Free Devices
Typical Applications
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MARKING
DIAGRAM
7
NCP1338P
AWL
YYWWG
PDIP-7
P SUFFIX
CASE 626B
1
8
P1338
ALYWG
G
SOIC-7
D SUFFIX
CASE 751U
1
A
= Assembly Location
WL, L = Wafer Lot
YY, Y = Year
WW, W = Work Week
G, G
= Pb-Free Package
(Note: Microdot may be in either location)
PIN CONNECTIONS
BO
FB
1
8
HV
2
3
6
4
5
CS
GND
VCC
DRV
(Top View)
ORDERING INFORMATION
Device
Package
Shipping†
NCP1338PG
PDIP-7
(Pb-Free)
50 Units/Rail
NCP1338DR2G
SOIC-7
(Pb-Free)
2500 Tape & Reel
†For information on tape and reel specifications,
including part orientation and tape sizes, please
refer to our Tape and Reel Packaging Specification
Brochure, BRD8011/D.
•Ac-dc Adapters for Notebooks, etc.
•Offline Battery Chargers
•Consumer Electronics (DVD Players, Set-Top Boxes, TVs, etc.)
•Auxiliary Power Supplies (USB, Appliances, TVs, etc.)
© Semiconductor Components Industries, LLC, 2008
April, 2008 - Rev. 0
1
Publication Order Number:
NCP1338/D
NCP1338
PIN FUNCTION DESCRIPTION
Pin No.
Symbol
1
BO
Function
Description
•
Brown-out and external
triggering
•
•
2
FB
•
Sets the peak current
setpoint
•
3
CS
•
Current sense input and
overpower compensation
adjustment
•
4
GND
IC ground
5
DRV
Output driver
•
6
VCC
IC supply
•
•
8
HV
•
High-voltage pin
By connecting this pin to the input voltage through a resistor divider, the
controller ensures operation at a safe mains level, thanks to a 500 mV
brown-out comparator.
If an external event brings this pin above 3.0 V, the controller's output is
disabled.
If an external event brings this pin above 5.0 V, the controller is
permanently latched-off.
By connecting an optocoupler or an auxiliary winding to this pin, the peak
current setpoint is adjusted accordingly to the output power demand.
When the requested peak current setpoint is below the internal standby
level, the device enters Soft-Skip mode.
This pin senses the primary current and routes it to the internal comparator
via an L.E.B.
Inserting a resistor in series with the pin allows to control the overpower
compensation level.
To be connected to an external MOSFET.
Connected to a tank capacitor (and possibly an auxiliary winding).
When VCC reaches 18.6 V, an internal OVP stops the output pulses.
Connected to the high-voltage rail, this pin injects a constant current into
the VCC bulk capacitor and ensures a clean lossless startup sequence.
VOUT
+
VCC
NCP1338
BO
1
+
Cbulk
8
+
2
3
6
4
5
VCC
Rcomp
Figure 1. Typical Application Schematic
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2
NCP1338
+
+
5V
Q
S
PERM. LATCH
R
DISABLE
+
-
+
3V
8 ms
timeout
Vdd
35 ms
max Toff
VCC < 4 V
Vdd
TSD
TSD
10 mA
BO
S
Startup
VBO
+
+
-
Soxyless
7.5 ms min
period
Ton
BOK
Clk
D
OVP
+
100 mV
Vdd 130 mV
+
Skip
Ton
Ton
VCC
Q
Q
Inhib
Toff
R1
SStart
500 mV
5.5 ms
blanking
Toff
Soxyless
demag
detection
R2
67 ms
max Ton
SSkip
Soxyless
FB
Setpoint
3V
20 kHz
Low-pass
filter
+
500 mV
Vdd
VBO
CS
FAULT
if Zener
activated
70 mA x VBO - 35 mA
TSD
CS
comp.
300 ms
Soft-Skip t
4 ms
Soft-Ski
p
12 V
10 V
5V
HV
+
+
-
PERM.
LATCH
FAULT
Management*
9.5 mA or
600 mA
VCC
SSkip
SStart
OVP
+
Ton
4k
GND
DRV
+
18.6 V
350 ns
LEB
FAULT
2p
(*If FAULT duration > 80 ms = > STOP
Restart when 2nd time VCC = VCCon)
Figure 2. Internal Circuit Architecture
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NCP1338
MAXIMUM RATINGS
Rating
Symbol
Value
Unit
VHV
-0.3 to 500
V
-
20
mA
VCCmax
-0.3 to 20
V
Maximum Current in Pin 6 (VCC)
-
"30
mA
Maximum Voltage on all Pins except Pin 8 (HV), Pin 6 (VCC) and Pin 5 (DRV)
-
-0.3 to 10
V
Maximum Current into all Pins except Pin 8 (HV), Pin 6 (VCC) and Pin 5 (DRV)
-
"10
mA
Maximum Current into Pin 6 (DRV) during ON Time and TBLANK
-
"1.0
A
Maximum Current into Pin 6 (DRV) after TBLANK during OFF Time
-
"15
mA
Thermal Resistance, Junction-to-Case
RqJC
57
°C/W
Thermal Resistance, Junction-to-Air, SOIC Version
RqJA
178
°C/W
Thermal Resistance, Junction-to-Air, DIP Version
RqJA
100
°C/W
Voltage on Pin 8 (HV) when Pin 6 (VCC) is Decoupled to Ground with 10 mF
Maximum Current in Pin 8 (HV)
Power Supply Voltage, Pin 6 (VCC) and Pin 5 (DRV)
TJMAX
150
°C
Operating Temperature Range
-
-40 to +125
°C
Storage Temperature Range
-
-60 to +150
°C
ESD Capability, HBM Model per Mil-std-883, Method 3015 (All Pins except HV)
-
2.0
kV
ESD Capability, Machine Model
-
200
V
Maximum Junction Temperature
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 contains latchup protection and exceeds 100 mA per JEDEC standard JESD78.
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NCP1338
ELECTRICAL CHARACTERISTICS (For typical values TJ = 25°C, for min/max values TJ = 0°C to +125°C, Max TJ = 150°C,
VCC = 11 V, unless otherwise noted.)
Characteristic
Pin
Symbol
Min
Typ
Max
Unit
VCC Increasing Level at which the Controller Starts
6
VCCON
11
12
13
V
VCC Decreasing Level at which the Controller Stops
6
VCCMIN
9.0
10
11
V
Protection Mode is Activated if VCC reaches this Level whereas the HV
Current Source is ON
6
VCCOFF
-
9.0
-
V
VCC Decreasing Level at which the Latch-Off Phase Ends
6
VCCLATCH
3.6
5.0
6.0
V
Margin between VCC Level at which Latch Fault is Released and
VCCLATCH
-
VMARGIN
0.3
-
-
V
VCC Increasing Level at which the Controller Enters Protection Mode
6
VCCOVP
17.6
18.6
19.6
V
VCC Level below which HV Current Source is Reduced
6
VCCINHIB
-
1.5
-
V
Internal IC Consumption, No Output Load on Pin 5, FSW = 60 kHz
6
ICC1
-
1.2
-
mA
Internal IC Consumption, 1.0 nF Output Load on Pin 5, FSW = 60 kHz
6
ICC2
-
2.0
-
mA
Internal IC Consumption, Latch-Off Phase, VCC = 8.0 V
6
ICC3
-
600
-
mA
Internal IC Consumption in Skip
6
ICCLOW
-
600
-
mA
Minimum Guaranteed Startup Voltage on HV Pin
8
VHVmin
-
-
55
V
High-Voltage Current Source when VCC > VCCINHIB
(VCC = 10.5 V, VHV = 60 V)
8
IC1
5.5
9.5
15
mA
High-Voltage Current Source when VCC < VCCINHIB
(VCC = 0 V, VHV = 60 V)
8
IC2
0.3
0.6
1.1
mA
Leakage Current Flowing when the HV Current Source is OFF
(VCC = 17 V, VHV = 500 V)
8
IHVLeak
-
-
90
mA
Output Voltage Rise-Time @ CL = 1.0 nF, 10-90% of Output Signal
5
TR
-
50
-
ns
Output Voltage Fall-Time @ CL = 1.0 nF, 10-90% of Output Signal
5
TF
-
20
-
ns
Source Resistance
5
ROH
-
20
-
W
Sink Resistance
5
ROL
-
8.0
-
W
Temperature Shutdown
-
TSD
130
-
-
°C
Hysteresis on Temperature Shutdown
-
-
-
30
-
°C
Maximum Internal Current Setpoint (@ IFB = IFB100%)
3
VCSLimit
475
500
525
mV
Minimum Internal Current Setpoint (@ IFB = IFBrippleIN)
3
VCSrippleIN
-
100
-
mV
Internal Current Setpoint for IFB = IFBrippleOUT
3
VCSrippleOUT
-
130
-
mV
Propagation Delay from Current Detection to Gate OFF State
3
TDEL
-
120
150
ns
Leading Edge Blanking Duration
3
TLEB
-
350
-
ns
Internal Current Offset Injected on the CS Pin during ON Time
(Over Power Compensation)
@ 1.0 V on Pin 1 and Vpin3 = 0.5 V
@ 2.0 V on Pin 1 and Vpin3 = 0.5 V
3
IOPC
Maximum ON Time
5
SUPPLY SECTION
INTERNAL STARTUP CURRENT SOURCE
DRIVE OUTPUT
TEMPERATURE SHUTDOWN
CURRENT COMPARATOR
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5
MaxTON
mA
-
35
105
-
52
67
82
ms
NCP1338
ELECTRICAL CHARACTERISTICS (continued) (For typical values TJ = 25°C, for min/max values TJ = 0°C to +125°C,
Max TJ = 150°C, VCC = 11 V, unless otherwise noted.)
Characteristic
Pin
Symbol
Min
Typ
Max
Unit
FB Current under which FAULT is Detected
2
IFBopen
-
40
-
mA
FB Current for which Internal Setpoint is 100%
2
IFB100%
-
50
-
mA
FB Current above which DRV Pulses are Stopped
2
IFBrippleIN
-
220
-
mA
FB Current under which DRV Pulses are Reauthorized after having
reached IFBrippleIN
2
IFBrippleOUT
-
205
-
mA
FB Current above which FB Pin Voltage is not Regulated anymore
2
IFBregMax
-
500
-
mA
FB Pin Voltage when IFBopen < IFB < IFBregMax
2
VFB
2.8
3.0
3.2
V
Duration before Entering Protection Mode after FAULT Detection
-
TFAULT
-
80
-
ms
Internal Soft-Skip Duration (Up to VCSLimit)
-
TSS
-
4.0
-
ms
Internal Soft-Skip Duration (Up to VCSLimit)
-
TSSkip
-
300
-
ms
Brown-Out Detection Level
1
VBO
460
500
540
mV
Current Flowing out of Pin 1 when Brown-Out Comparator has Toggled
1
IBO
-
10
-
mA
Vpin1 Threshold that Disables the Output
1
VDISABLE
2.8
3.0
3.3
V
Vpin1 Threshold that Activates the Permanent Latch
1
VLATCH
4.75
5.0
5.25
V
Current Threshold for Demagnetization Detection
5
ISOXYth
-
210
-
mA
Max Voltage on DRV Pin During OFF Time after TBLANK
(when Sinking 15 mA)
5
VDRVlowMAX
-
-
1.5
V
Min Voltage on DRV Pin During OFF Time after TBLANK
(when Sourcing 15 mA)
5
VDRVlowMIN
-0.6
-
-
V
Propagation Delay from Demag Detection to Gate ON State
(IGATE Slope of 500 A/s)
5
TDMG
-
180
220
ns
Blanking Window after Gate OFF State before Detecting
Demagnetization
5
TBLANK
-
5.5
-
ms
Timeout on Demag Signal
5
TOUT
-
8.0
-
ms
Maximum OFF Time
5
MaxTOFF
-
35
42
ms
Minimum Switching Period
5
MinPeriod
6.8
7.7
8.5
ms
FEEDBACK SECTION
BROWN-OUT AND LATCH SECTION
DEMAGNETIZATION DETECTION BLOCK
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NCP1338
APPLICATION INFORMATION
INTRODUCTION
The NCP1338 implements a standard current mode
architecture where the switch-off time is dictated by the
peak current setpoint, whereas the core-reset detection
triggers the turn-on event. This component represents
the ideal candidate where low part-count is the key
parameter, particularly in low-cost ac-dc adapters,
consumer electronics, auxiliary supplies, etc. Due to
its high-performance, high-voltage technology, the
NCP1338 incorporates all the necessary features needed to
build a rugged and reliable Switch-Mode Power Supply
(SMPS):
• Quasi-Resonant Operation: Valley-switching
operation is ensured whatever the operating conditions
are, due to the internal soxyless circuitry. As a result,
there are virtually no primary switch turn-on losses,
and no secondary diode recovery losses, and EMI and
video noise perturbations are reduced. The converter
also stays a first-order system and accordingly eases
the feedback loop design.
• Dynamic Self-Supply (DSS): Due to its Very High
Voltage Integrated Circuit (VHVIC) technology,
ON Semiconductor's NCP1338 allows for a direct pin
connection to the high-voltage DC rail. A dynamic
current source charges up a capacitor and thus
provides a fully independent VCC level. As a result,
low power applications will not require any auxiliary
winding to supply the controller. In applications
where this winding is anyway required (see “Power
Dissipation” section in the application note), the DSS
will simplify the VCC capacitor selection.
• Overcurrent Protection (OCP): When the feedback
current is below minimum value, a fault is detected. If
this fault is present for more than 80 ms, NCP1338
enters an auto-recovery soft burst mode. All pulses are
stopped and the VCC capacitor discharges down to
5.0 V. Then, by monitoring the VCC level, the startup
current source is activated ON and OFF to create a
burst mode. After the current source being activated
twice, the controller tries to restart, with a 4.0 ms
Soft-Skip. If the fault has gone, the SMPS resumes
•
•
•
•
•
operation. If the fault is still there, the burst sequence
starts again. The Soft-Skip, together with a minimum
frequency clamp, allow to reduce the noise generated
in the transformer in short-circuit conditions.
Overvoltage Protection (OVP): By continuously
monitoring the VCC voltage level, the NCP1338 stops
switching whenever an overvoltage condition is
detected.
Brown-Out Detection (BO): By monitoring the level
on Pin 1 during normal operation, the controller
protects the SMPS against low mains condition. When
Pin 1 level falls below 500 mV, the controller stops
pulsing until this level goes back and resumes
operation. By adjusting the resistor divider connected
between the high input voltage and this pin, start and
stop levels are programmable.
Over Power Compensation (OPC): An internal
current source injects out of Pin 3 (CS pin) a current
proportional to the voltage applied on Pin 1. As this
voltage is an image of the input voltage, by inserting a
resistor in series with Pin 3, it is possible to create an
offset on the current sense signal that will compensate
the effect of the input voltage variation.
External Latch Trip Point: By externally forcing a
level on Pin 1 (e.g., with a signal coming from a
temperature sensor) greater than 3.0 V (but below
5.0 V), it is possible to disable the output of the
controller. If the voltage is forced over 5.0 V, the
controller is permanently latched-off: to resume
normal operation, the VCC voltage should go below
4.0 V, which implies to unplug the SMPS from the
mains.
Standby Ability: Under low load conditions,
NCP1338 enters a Soft-Skip mode: when the CS
setpoint becomes lower than 20% of the maximum
peak current, output pulses are stopped, then switching
is starting again when FB loop forces a setpoint higher
than 25%. As this occurs at low peak current, with
Soft-Skip activated, and as the TOFF is clamped,
noise-free operation is guaranteed, even with a cheap
transformer.
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NCP1338
Timing Diagrams
VCC
VCCON
VCCMIN
At startup, a 4.0 ms Soft-Skip is activated.
If the current Setpoint is above the fault
level, FAULT flag is raised.
CS
Setpoint
Fault
VCSstby
CS
VCSLimit
FAULT
TIMER
SS
When FAULT is activated,
the 80 ms timer starts.
80 ms
When the timer ends, if FAULT is not activated
anymore, the controller works normally.
Figure 3. Startup Sequence
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NCP1338
Restart on 2nd cycle
VCC
VCCON
VCCMIN
VCCLATCH
CS
Setpoint
Overload is removed here
Overload
Fault
When the current setpoint rises above
fault level, FAULT flag is activated.
CS
VCSLimit
Output pulses
are stopped.
FAULT
SS
TIMER
80 ms
When FAULT flag
is activated, timer
is restarted.
80 ms Fault Timer
Normal Startup
Figure 4. Overload
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NCP1338
VCC
VCCon
VCCmin
CS
Setpoint
VCSrippleOUT
VCSrippleIN
CS
(envelope)
Min TON
Soft-Skip on
each re-start
Figure 5. Soft-Skip Mode in Standby
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NCP1338
Soxyless
The “Valley point detection” is based on the observation
of the Power MOSFET Drain voltage variations. When the
transformer is fully demagnetized, the Drain voltage
evolution from the plateau level down to the VIN asymptote
is governed by the resonating energy transfer between the
LP transformer inductor and the global capacitance present
on the Drain. These voltage oscillations create current
oscillation in the parasitic capacitor across the switching
Lprim
MOSFET (modelized by the Crss capacitance between
Gate and Drain): a negative current (flowing out of DRV
pin) takes place during the decreasing part of the Drain
oscillation, and a positive current (entering into the DRV
pin) during the increasing part.
The Drain valley corresponds to the inversion of the
current (i.e., the zero crossing): by detecting this point, we
always ensure a true valley turn-on.
TSWING
Vswitch
Crss
Isoxy
DRV
t
Figure 6. Soxyless Concept
The current in the Power MOSFET gate is:
Igate = Vringing/Zc (with Zc the capacitance impedance)
so
Igate = Vringing S (2 S p S Fres S Crss)
The magnitude of this gate current depends on the
MOSFET, the resonating frequency and the voltage swing
present on the Drain at the end of the plateau voltage.
The dead time TSWING is given by the equation:
Tswing + 0.5ńFres + p * ǸLp * Cdrain
Drain. This capacitance includes the snubber capacitor if
any, the transformer windings stray capacitance plus the
parasitic MOSFET capacitances COSS and CRSS).
Internal Feedback Circuitry
To simplify the implementation of a primary regulation,
it is necessary to inject a current into the FB pin (instead of
sourcing it out). But to have a precise primary regulation,
the voltage present on FB pin must be regulated. Figure 8
gives the FB pin internal implementation: the circuitry
combines the functions of a current to voltage converter
and a voltage regulator.
(eq. 1)
(where LP is the primary transformer inductance and
CDRAIN the total capacitance present on the MOSFET
Vdd
FB
+
3V
+
-
Internal
Setpoint
20 kHz
Low-pass Filter
Figure 7. Internal Implementation of FB Pin
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NCP1338
VCCLATCH, maintaining VCC between 5.0 V and 12 V):
the controller stays in this position until the VCC voltage is
decreased below 4.0 V, i.e., when the power supply is
unplugged from the mains (in normal operation, as soon as
a voltage is present on the HV pin, VCC is always kept
above 5.0 V).
The input information is the current injected in FB pin by
the feedback loop. The range of current is from 40 mA for
overload detection to 220 mA corresponding to VCSrippleIN.
In transients, currents from 0 to more than 400 mA may also
appear: the circuitry is able to sustain them.
To regulate the FB pin voltage, the operational amplifier
needs to have a high gain and a wide bandwidth. But the
feedback information used internally needs to be filtered,
because we don't want the controller to be sensitive to the
switching noise. For this purpose, a 20 kHz filter is added
after the shunt regulator, and any reading of the feedback
signal (for ripple mode, fault detection, or setpoint
elaboration) is done after.
Soft-Skip Mode
The NCP1338 implements a Soft-Skip mode with a large
hysteresis on the skip comparator in order to ensure a
noise-free and high-efficiency operation in low-load
conditions (standby). When internal setpoint is reaching
VCSrippleIN = 100 mV (corresponding to 20% of the
maximum setpoint), the output pulses are stopped. Then
FB loop asks for more power and internal setpoint is
increasing: when it reaches VCSrippleOUT = 130 mV
(corresponding to 25% of the maximum setpoint), the
output starts pulsing again. Soft-Skip is activated in each
activity following a stop period. See Figure 5 for detailed
timing diagram.
Soft Burst Mode (Protection Mode)
The NCP1338 features a fault timer to detect an overload
completely independently of the VCC voltage. As soon as
the feedback loop asks for the maximum power, a fault is
detected, and an internal timer is started. When the fault
disappears the timer is reset, but if the timer reaches 80 ms,
the protection mode is activated.
Once this protection is toggled, output pulses are stopped
and DSS is deactivated (HV current source turn-on
threshold changes from VCCMIN to VCCLATCH). VCC
slowly decreases (the current consumption is ICC3), and
the HV current source is switched ON when VCC reaches
VCCLATCH. As a result VCC increases until VCCON, but the
controller does not start as the output is still forced low.
VCC decreases again down to VCCLATCH, and a new
start-up cycle occurs. On the second attempt, the output is
released, and NCP1338 effectively starts, with the
Soft-Skip activated. Figure 4 illustrates this behavior.
HV Current Source
NCP1338 features a DSS, to allow operation without any
auxiliary voltage. But to protect the die in case of
short-circuit on VCC pin, the current delivered by the HV
current source is lowered when VCC voltage is below 1.5 V.
In the case the current consumed on the DRV pin is
higher than the DSS capability (high Qg MOSFET or
failure), the HV current source is switched ON when VCC
reaches VCCMIN, but the voltage on VCC pin keep on
decreasing. If there is no UVLO threshold to stop the DRV
pulses, the gate voltage will become too low and the risk is
high to destroy the MOSFET. NCP1338 features an
additional comparator, which threshold is 9.0 V: when VCC
reaches this level whereas the HV current source is ON,
DRV pulses are stopped and the protection mode is
activated.
Safety Features
The NCP1338 includes several safety features to help the
power supply designer to build a rugged design:
• OVP (Overvoltage on VCC): Activated when voltage
on pin VCC is higher than 18.6 V
• Brown-Out (Undervoltage lockout on bulk voltage):
Activated when voltage on pin BO is below 500 mV
• Disable (Comparator activated by an external signal):
Activated when the voltage on BO pin is higher than
3.0 V but below 5.0 V
• TSD (Temperature shutdown): Typically activated
when the die temperature is above 150°C, released at
120°C
Brown-Out
The brown-out protection comparator has a fixed
reference of 500 mV. When the comparator is activated
(i.e., when the input voltage VIN is above the starting level),
a 10 mA internal current source is activated and creates an
offset across the bottom resistor of the external resistor
divider. It gives the minimum hysteresis of the brown-out
protection. By adding a series resistor between the divider
and the BO pin, it is possible to adjust (increase) the
hysteresis.
The BO pin also features two additional comparators: the
first one (that toggles at 3.0 V) stops the DRV pulses,
whereas the second one (that toggles at 5.0 V) permanently
latches off the controller (the VCC should be forced below
4.0 V to release the latch).
When the BO or Enable comparator toggles, the fault
timer is reset, preventing the controller from going into
protection mode if the condition lasts longer than Tfault.
Figure 8 gives the internal implementation of the BO pin.
All these events have the same consequence for the
controller: the DRV pulses are stopped, and the fault timer
is reset. When the condition disappears, the controller
restarts with the Soft-Skip activated.
• Permanent Latch (Comparator activated by an external
signal): Activated when the voltage on BO pin is
above 5.0 V
When this comparator is activated, the DRV pulses are
stopped, and the DSS is deactivated (only the start-up
current source is turned on each time VCC reaches
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12
NCP1338
+
5V
+
-
Permanent Latch
+
3V
Vin
Enable
+
Vdd
10 mA current source activated
when VBOK is high
3.3 meg
Rhyst
BO
+
+
11 k
-
500 mV
Figure 8. Internal Implementation of BO Pin
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13
BOK
NCP1338
PACKAGE DIMENSIONS
PDIP-7
P SUFFIX
CASE 626B-01
ISSUE A
NOTES:
1. DIMENSIONS AND TOLERANCING PER
ASME Y14.5M, 1994.
2. DIMENSIONS IN MILLIMETERS.
3. DIMENSION L TO CENTER OF LEAD
WHEN FORMED PARALLEL.
4. PACKAGE CONTOUR OPTIONAL (ROUND
OR SQUARE CORNERS).
5. DIMENSIONS A AND B ARE DATUMS.
J
8
5
M
B
1
L
4
DIM
A
B
C
D
F
G
H
J
K
L
M
N
F
A
NOTE 2
C
MILLIMETERS
MIN
MAX
9.40 10.16
6.10
6.60
3.94
4.45
0.38
0.51
1.02
1.78
2.54 BSC
0.76
1.27
0.20
0.30
2.92
3.43
7.62 BSC
--10 °
0.76
1.01
-TN
SEATING
PLANE
H
D
K
G
0.13 (0.005)
M
T A
M
B
M
SOIC-7
D SUFFIX
CASE 751U-01
ISSUE D
-A8
NOTES:
1. DIMENSIONING AND TOLERANCING PER
ANSI Y14.5M, 1982.
2. CONTROLLING DIMENSION: MILLIMETER.
3. DIMENSION A AND B ARE DATUMS AND T
IS A DATUM SURFACE.
4. DIMENSION A AND B DO NOT INCLUDE
MOLD PROTRUSION.
5. MAXIMUM MOLD PROTRUSION 0.15 (0.006)
PER SIDE.
5
-B- S
0.25 (0.010)
B
M
M
1
4
G
C
R
X 45 _
J
-T-
SEATING
PLANE
H
0.25 (0.010)
K
M
D 7 PL
M
T B
S
A
S
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14
DIM
A
B
C
D
G
H
J
K
M
N
S
MILLIMETERS
MIN
MAX
4.80
5.00
3.80
4.00
1.35
1.75
0.33
0.51
1.27 BSC
0.10
0.25
0.19
0.25
0.40
1.27
0_
8_
0.25
0.50
5.80
6.20
INCHES
MIN MAX
0.189 0.197
0.150 0.157
0.053 0.069
0.013 0.020
0.050 BSC
0.004 0.010
0.007 0.010
0.016 0.050
0_
8_
0.010 0.020
0.228 0.244
NCP1338
Soft-Skip is a trademark of Semiconductor Components Industries, LLC (SCILLC).
The product described herein (NCP1338), may be covered by the following U.S. patents: 6,362,067, 5,073,850, 6,385,060, 6,587,357,
6,469,484, 6,940,320, 5,862,045. There may be other patents pending.
ON Semiconductor and
are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC reserves the right to make changes without further notice
to any products herein. SCILLC makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does SCILLC assume any
liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation special, consequential or incidental
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time. All operating parameters, including “Typicals” must be validated for each customer application by customer's technical experts. SCILLC does not convey any license under
its patent rights nor the rights of others. SCILLC products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body,
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NCP1338/D