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NCP1253ASN100T1G

P1-P3P4-P6P7-P9P10-P12P13-P15
NCP1253
www.onsemi.com
13
F
sw
V
FB
V
CS
V
FB
65 kHz
26 kHz
350 mV
V
fold
3.4 V
V
fold
3.4 V
0.8 V
[0.36 V
FB
V
freeze
[0.25 V
1.05 V 1.5 V
1.5 V
max
min
max
min
V
fold,end
Frequency Peak current setpoint
F
sw
V
FB
V
CS
V
FB
65 kHz
26 kHz
350 mV
V
fold
3.4 V
V
fold
3.4 V
0.8 V
[0.36 V
FB
V
freeze
[0.25 V
1.05 V 1.5 V
1.5 V
max
min
max
min
V
fold,end
Frequency Peak current setpoint
Figure 27. By Observing the Voltage on the Feedback Pin, the Controller Reduces its Switching Frequency for an
Improved Performance at Light Load
Auto−recovery Short−Circuit Protection
In case of output short−circuit or if the power supply
experiences a severe overloading situation, an internal error
flag is raised and starts a countdown timer. If the flag is
asserted longer than 100 ms, the driving pulses are stopped
and V
CC
falls down as the auxiliary pulses are missing.
When it crosses VCC
(min)
, the controller consumption is
down to a few mA and the V
CC
slowly builds up again thanks
to the resistive starting network. When V
CC
reaches
VCC
ON
, the controller attempts to re−start, checking for the
absence of the fault. If the fault is still there, the supply enters
another cycle of so−called hiccup. If the fault has
disappeared, the power supply resumes operations. Please
note that the soft−start is activated during each of the re−start
sequence.
1
vcc
2
vdrv
3
ilprim
500u 1.50m 2.50m 3.50m 4.50m
time in seconds
445m
1.41
2.38
3.35
4.32
ilprim in amperes
−8.13
−2.12
3.89
9.90
15.9
vcc in volts
−11.5
−2.72
6.05
14.8
23.6
vdrv in volts
Plot1
2
1
3
()
cc
Vt
()
DRV
Vt
()
p
L
It
SS
1
vcc
2
vdrv
3
ilprim
500u 1.50m 2.50m 3.50m 4.50m
time in seconds
445m
1.41
2.38
3.35
4.32
ilprim in amperes
−8.13
−2.12
3.89
9.90
15.9
vcc in volts
−11.5
−2.72
6.05
14.8
23.6
vdrv in volts
Plot1
2
1
3
()
cc
Vt
()
DRV
Vt
()
p
L
It
SS
Figure 28. An Auto−Recovery Hiccup Mode is Entered in Case a Faulty Event Longer Than 100 ms is
Acknowledged by the Controller
Ramp compensation
The NCP1253 includes an internal ramp compensation
signal. This is the buffered oscillator clock delivered during
the on time only. Its amplitude is around 2.5 V at the
maximum duty−cycle. Ramp compensation is a known
means used to cure sub harmonic oscillations in
CCM−operated current−mode converters. These
oscillations take place at half the switching frequency and
occur only during Continuous Conduction Mode (CCM)
with a duty−cycle greater than 50%. To lower the current
loop gain, one usually injects between 50% and 100% of the
inductor downslope.
NCP1253
www.onsemi.com
14
Rsense
Rcomp
20k
0V
2.5 V
CS
+
−
L.E.B
from FB
setpoint
latch
reset
ON
Figure 29. Inserting a Resistor in Series with the Current Sense Information Brings Ramp Compensation and
Stabilizes the Converter in CCM Operation
In the NCP1253 controller, the oscillator ramp features a
2.5 V swing. If the clock operates at a 65 kHz frequency,
then the available oscillator slope corresponds to:
S
ramp
+
V
ramp,peak
D
max
T
SW
+
2.5 0.8
15m
+ 133 kVńsor133mVńms
(eq. 6)
In our flyback design, let’s assume that our primary
inductance L
p
is 770 mH, and the SMPS delivers 19 V with
a N
p
:N
s
ratio of 1:0.25. The off−time primary current slope
S
p
is thus given by:
S
P
+
ǒ
V
out
) V
f
Ǔ
N
s
N
P
L
P
+
(
19 ) 0.8
)
4
770m
+ 103 kAńs
(eq. 7)
Given a sense resistor of 330 mW, the above current ramp
turns into a voltage ramp of the following amplitude:
S
sense
+ S
P
R
sense
+ 103k 0.33
+ 34 kVńsor34mVńms
(eq. 8)
If we select 50% of the downslope as the required amount
of ramp compensation, then we shall inject a ramp whose
slope is 17 mV/ms. Our internal compensation being of
133 mV/ms, the divider ratio (divratio) between R
comp
and
the internal 20 kW resistor is:
divratio +
17m
133m
+ 0.127
(eq. 9)
The series compensation resistor value is thus:
R
comp
+ R
ramp
divratio + 20k 0.127 [ 2.5 kW
(eq. 10)
A resistor of the above value will then be inserted from the
sense resistor to the current sense pin. We recommend
adding a small 100 pF capacitor, from the current sense pin
to the controller ground for improved noise immunity.
Please make sure both components are located very close to
the controller.
NCP1253
www.onsemi.com
15
PACKAGE DIMENSIONS
TSOP−6
CASE 318G−02
ISSUE U
23
456
D
1
e
b
E1
A1
A
0.05
NOTES:
1. DIMENSIONING AND TOLERANCING PER ASME Y14.5M, 1994.
2. CONTROLLING DIMENSION: MILLIMETERS.
3. MAXIMUM LEAD THICKNESS INCLUDES LEAD FINISH. MINIMUM
LEAD THICKNESS IS THE MINIMUM THICKNESS OF BASE MATERIAL.
4. DIMENSIONS D AND E1 DO NOT INCLUDE MOLD FLASH,
PROTRUSIONS, OR GATE BURRS. MOLD FLASH, PROTRUSIONS, OR
GATE BURRS SHALL NOT EXCEED 0.15 PER SIDE. DIMENSIONS D
AND E1 ARE DETERMINED AT DATUM H.
5. PIN ONE INDICATOR MUST BE LOCATED IN THE INDICATED ZONE.
c
*For additional information on our Pb−Free strategy and soldering
details, please download the ON Semiconductor Soldering and
Mounting Techniques Reference Manual, SOLDERRM/D.
SOLDERING FOOTPRINT*
DIM
A
MIN NOM MAX
MILLIMETERS
0.90 1.00 1.10
A1 0.01 0.06 0.10
b 0.25 0.38 0.50
c 0.10 0.18 0.26
D 2.90 3.00 3.10
E 2.50 2.75 3.00
e 0.85 0.95 1.05
L 0.20 0.40 0.60
0.25 BSC
L2
−
0° 10°
STYLE 13:
PIN 1. GATE 1
2. SOURCE 2
3. GATE 2
4. DRAIN 2
5. SOURCE 1
6. DRAIN 1
1.30 1.50 1.70
E1
E
RECOMMENDED
NOTE 5
L
C
M
H
L2
SEATING
PLANE
GAUGE
PLANE
DETAIL Z
DETAIL Z
0.60
6X
3.20
0.95
6X
0.95
PITCH
DIMENSIONS: MILLIMETERS
M
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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.
P
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Phone: 81−3−5817−1050
NCP1253/D
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P1-P3P4-P6P7-P9P10-P12P13-P15

NCP1253ASN100T1G

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Manufacturer:
ON Semiconductor
Description:
Switching Controllers Current Mode PWM Offline Controller
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