NCP1081
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16
Current Limit Comparator
The NCP1081 current limit block behind the CS pin
senses the current flowing in the external MOSFET for
current mode control and cyclebycycle current limit. This
is performed by the current limit comparator which, on the
CS pin, senses the voltage across the external Rcs resistor
located between the source of the MOSFET and the ARTN
pin.
The NCP1081 also provides a blanking time function on
CS pin which ensures that the current limit and PWM
comparators are not prematurely trigged by the current spike
that occurs when the switching MOSFET turns on.
Slope Compensation Circuitry
To overcome subharmonic oscillations and instability
problems that exist with converters running in continuous
conduction mode (CCM) and when the duty cycle is close
or above 50 percent, the NCP1081 integrates a current slope
compensation circuit. The amplitude of the added slope
compensation is typically 110 mV over one cycle.
As an example, for an operating switching frequency of
250 kHz, the internal slope provided by the NCP1081 is
27.5 mV/ mA typically.
DCDC Controller Oscillator
The frequency is configured with the Rosc resistor
inserted between OSC and ARTN, and is defined by the
following equation:
R
OSC
(kW) +
38600
F
OSC
(kHz)
The duty cycle limit is fixed internally at 80 percent.
NCP1081
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17
PACKAGE DIMENSIONS
TSSOP20 EP
CASE 948AB01
ISSUE O
DIM
D
MIN MAX
6.60
MILLIMETERS
E1 4.30 4.50
A 1.10
A1 0.05 0.15
L 0.50 0.70
e 0.65 BSC
P --- 4.20
c 0.09 0.20
c1 0.09 0.16
b 0.19 0.30
b1 0.19 0.25
L2 0.25 BSC
M 0 8
__
NOTES:
1. DIMENSIONING AND TOLERANCING PER ASME
Y14.5M, 1994.
2. CONTROLLING DIMENSION: MILLIMETERS.
3. DIMENSION b DOES NOT INCLUDE DAMBAR
PROTRUSION. ALLOWABLE DAMBAR PROTRUSION
SHALL BE 0.07 IN EXCESS OF THE LEAD WIDTH AT
MMC. DAMBAR CANNOT BE LOACTED ON THE
LOWER RADIUS OR THE FOOT OF THE LEAD.
4. DIMENSIONS b, b1, c, c1 TO BE MEASURED BE-
TWEEN 0.10 AND 0.25 FROM LEAD TIP.
5. DATUMS A AND B ARE ARE DETERMINED AT DATUM
H. DATUM H IS LOACTED AT THE MOLD PARTING
LINE AND COINCIDENT WITH LEAD WHERE THE
LEAD EXITS THE PLASTIC BODY.
6. DIMENSION D DOES NOT INCLUDE MOLD FLASH,
PROTRUSIONS OR GATE BURRS. MOLD FLASH,
PROTRUSIONS OR GATE BURRS SHALL NOT
EXCEED 0.15 PER SIDE. DIMENSION E1 DOES NOT
INCLUDE INTERLEAD FLASH OR PROTRUSION. IN-
TERLEAD FLASH OR PROTRUSION SHALL NOT EX-
CEED 0.15 PER SIDE. D AND E1 ARE DETERMINED
AT DATUM H.
PIN 1
REFERENCE
D
E1
0.08
A
SECTION BB
b
b1
cc1
SEATING
PLANE
20X
b
E
e
DETAIL A
6.40
---
4.30
20X
0.98
20X
0.35
0.65
DIMENSIONS: MILLIMETERS
PITCH
SOLDERING FOOTPRINT*
L
L2
GAUGE
DETAIL A
e/2
DETAIL B
A2 0.85 0.95
E 6.40 BSC
P1 --- 3.00
PLANE
SEATING
PLANE
C
H
B
B
B
M
END VIEW
A-B
M
0.10 DC
TOP VIEW
SIDE VIEW
A-B0.20 D
C
110
1120
B
A
D
DETAIL B
2X 10 TIPS
A1
A2
C
0.05 C
C
P
P1
BOTTOM VIEW
3.106.76
20X
*For additional information on our PbFree strategy and soldering
details, please download the ON Semiconductor Soldering and
Mounting Techniques Reference Manual, SOLDERRM/D.
NCP1081
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18
ON Semiconductor and are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC owns the rights to a number of patents, trademarks,
copyrights, trade secrets, and other intellectual property. A listing of SCILLC’s product/patent coverage may be accessed at www.onsemi.com/site/pdf/PatentMarking.pdf. 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 damages. Typical” parameters which may be provided in SCILLC data sheets and/or specifications can and do vary in different applications
and actual performance may vary over 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, or other applications intended to support or sustain life, or for any other application in which the failure of the SCILLC product could create a situation where
personal injury or death may occur. Should Buyer purchase or use SCILLC products for any such unintended or unauthorized application, Buyer shall indemnify and hold SCILLC and
its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly,
any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that SCILLC was negligent regarding the design or manufacture
of the part. SCILLC is an Equal Opportunity/Affirmative Action Employer. This literature is subject to all applicable copyright laws and is not for resale in any manner.
PUBLICATION ORDERING INFORMATION
N. American Technical Support: 8002829855 Toll Free
USA/Canada
Europe, Middle East and Africa Technical Support:
Phone: 421 33 790 2910
Japan Customer Focus Center
Phone: 81358171050
NCP1081/D
LITERATURE FULFILLMENT:
Literature Distribution Center for ON Semiconductor
P.O. Box 5163, Denver, Colorado 80217 USA
Phone: 3036752175 or 8003443860 Toll Free USA/Canada
Fax: 3036752176 or 8003443867 Toll Free USA/Canada
Email: orderlit@onsemi.com
ON Semiconductor Website: www.onsemi.com
Order Literature: http://www.onsemi.com/orderlit
For additional information, please contact your local
Sales Representative

NCP1081DEG

Mfr. #:
Manufacturer:
ON Semiconductor
Description:
Switching Controllers POE-PD 40W DC-DC
Lifecycle:
New from this manufacturer.
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