NCP1124, NCP1126, NCP1129
www.onsemi.com
16
Adjustable Ramp Compensation
The NCP112x also include an internal ramp
compensation signal. This is the buffered oscillator clock
delivered during the on time only. Its amplitude V
ramp
is
around 2.5 V at maximum duty−cycle. Ramp compensation
is a well−known method used to eliminate the sub−harmonic
oscillations in CCM peak current mode converters. These
oscillations take place at half the switching frequency and
occur only during Continuous Conduction Mode (CCM)
with a duty−ratio greater than 50%. To lower the current
loop gain, one usually mixes between 50% and 100% of the
inductor downslope with the current−sense signal.
Figure 45 depicts how internally the ramp is generated. Note
that the ramp signal will be disconnected from the CS pin,
during the off−time.
Figure 45. Internal Adjustable Ramp
Compensation Architecture
In the NCP112x switchers, the oscillator ramp exhibits a
V
ramp
2.5 V swing reached at its maximum duty−ratio. If the
clock operates at a 65−kHz frequency, then the slope of the
ramp is equal to:
S
ramp
+
V
ramp
D
max
T
sw
(eq. 6)
The off−time primary current slope S
p
is thus given by
Equation 7:
S
p
+
ǒ
V
out
) V
f
Ǔ
N
p
N
s
L
p
(eq. 7)
Given a sense resistor R
sense
the above current ramp turns
into a voltage ramp of the following amplitude:
S
sense
+ S
p
R
sense
(eq. 8)
The slope of compensation ramp is chosen to be the same
as the downslope of the sensing ramp for better transient
response. The internal resistor connected to the
compensation ramp is 20 kW. The series compensation
resistor value is therefore:
R
comp
+ R
ramp
S
sense
S
ramp
(eq. 9)
A resistor of the above value will then be inserted from the
sense resistor to the current sense pin. A100 pF capacitor is
recommended to be added to the current sense pin to the
switcher ground for improved noise immunity with the
current sensing components located very close to the
switcher.
NCP1124, NCP1126, NCP1129
www.onsemi.com
17
Figure 46. Pin Connections
1
3
2
5
6
8
4
(Top View)
VCC
FB
CS
Source
GND
Drain
Drain
ORDERING INFORMATION
Device Package Shipping
NCP1124AP65G PDIP−7
(Pb−Free)
50 Units / Rail
NCP1124BP65G PDIP−7
(Pb−Free)
50 Units / Rail
NCP1124AP100G PDIP−7
(Pb−Free)
50 Units / Rail
NCP1124BP100G PDIP−7
(Pb−Free)
50 Units / Rail
NCP1126AP65G PDIP−7
(Pb−Free)
50 Units / Rail
NCP1126BP65G PDIP−7
(Pb−Free)
50 Units / Rail
NCP1126AP100G PDIP−7
(Pb−Free)
50 Units / Rail
NCP1126BP100G PDIP−7
(Pb−Free)
50 Units / Rail
NCP1129AP65G PDIP−7
(Pb−Free)
50 Units / Rail
NCP1129BP65G PDIP−7
(Pb−Free)
50 Units / Rail
NCP1129AP100G PDIP−7
(Pb−Free)
50 Units / Rail
NCP1129BP100G PDIP−7
(Pb−Free)
50 Units / Rail
NCP1124, NCP1126, NCP1129
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18
PACKAGE DIMENSIONS
PDIP−7 (PDIP−8 LESS PIN 7)
CASE 626B
ISSUE C
14
58
b2
NOTE 8
D
b
L
A1
A
eB
E
A
TOP VIEW
C
SEATING
PLANE
0.010 CA
SIDE VIEW
END VIEW
END VIEW
WITH LEADS CONSTRAINED
NOTES:
1. DIMENSIONING AND TOLERANCING PER ASME Y14.5M, 1994.
2. CONTROLLING DIMENSION: INCHES.
3. DIMENSIONS A, A1 AND L ARE MEASURED WITH THE PACK-
AGE SEATED IN JEDEC SEATING PLANE GAUGE GS−3.
4. DIMENSIONS D, D1 AND E1 DO NOT INCLUDE MOLD FLASH
OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS ARE
NOT TO EXCEED 0.10 INCH.
5. DIMENSION E IS MEASURED AT A POINT 0.015 BELOW DATUM
PLANE H WITH THE LEADS CONSTRAINED PERPENDICULAR
TO DATUM C.
6. DIMENSION E3 IS MEASURED AT THE LEAD TIPS WITH THE
LEADS UNCONSTRAINED.
7. DATUM PLANE H IS COINCIDENT WITH THE BOTTOM OF THE
LEADS, WHERE THE LEADS EXIT THE BODY.
8. PACKAGE CONTOUR IS OPTIONAL (ROUNDED OR SQUARE
CORNERS).
E1
M
8X
c
D1
B
H
NOTE 5
e
e/2
A2
NOTE 3
M
B
M
NOTE 6
M
DIM MIN MAX
INCHES
A −−−− 0.210
A1 0.015 −−−−
b 0.014 0.022
C 0.008 0.014
D 0.355 0.400
D1 0.005 −−−−
e 0.100 BSC
E 0.300 0.325
M −−−− 10
−− 5.33
0.38 −−
0.35 0.56
0.20 0.36
9.02 10.16
0.13 −−
2.54 BSC
7.62 8.26
−−− 10
MIN MAX
MILLIMETERS
E1 0.240 0.280 6.10 7.11
b2
eB −−−− 0.430 −− 10.92
0.060 TYP 1.52 TYP
A2 0.115 0.195 2.92 4.95
L 0.115 0.150 2.92 3.81
°°
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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
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NCP1126/D
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NCP1124AP100G

Mfr. #:
Manufacturer:
ON Semiconductor
Description:
AC/DC Converters HV SWITCHER FOR OFFLINE P
Lifecycle:
New from this manufacturer.
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