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Número de pieza NCP4355A
Descripción Secondary Side SMPS OFF Mode Controller
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NCP4355
Secondary Side SMPS OFF
Mode Controller for Low
Standby Power
Description
The NCP4355 is a secondary side SMPS controller designed for use
in applications which require extremely low no load power
consumption. The device is capable of detecting “no load” conditions
and entering the power supply into a low consumption OFF mode.
During OFF mode, the primary side controller is turned off and energy
is provided by the output capacitors thus eliminating the power
consumption required to maintain regulation. During OFF mode, the
output voltage relaxes and is allowed to decrease to an adjustable
level. Once more energy is required, the NCP4355 automatically
restarts the primary side controller by ONOFF current that flows
through ONOFF optocoupler. The NCP4355 controls the primary
controller with an “Active ON” signal, meaning that it only drives
optocoupler current during ON mode to minimize consumption during
OFF mode.
During normal power supply operation, the NCP4355 provides
integrated voltage feedback regulation, replacing the need for a shunt
regulator. The A and C versions include a current regulation loop in
addition to voltage regulation.
The NCP4355 includes a LED driver pin (except C version)
implemented with an open drain MOSFET driven by a 1 kHz square
wave with a 12.5% duty cycle for indication purpose.
The NCP4355 is available in SOIC8 package.
DEVICE OPTIONS
Adjustable Vmin
Current Regulation
LED driver
NCP4355A
No
Yes
Yes
NCP4355B
Yes
No
Yes
NCP4355C
Yes
Yes
No
Features
Operating Input Voltage Range: 3.5 V to 36.0 V
Supply Current < 100 mA
±0.5% Reference Voltage Accuracy (TJ = 25°C)
Constant Voltage and Constant Current (A and C versions) Control
Loop
Indication LED PWM Modulated Driver (except NCP4355C)
These Devices are PbFree, Halogen Free/BFR Free and are RoHS
Compliant
Typical Applications
Offline Adapters for Notebooks, Game Stations and Printers
High Power ACDC Converters for TVs, SetTop Boxes, Monitors etc.
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8
1
SOIC8
D SUFFIX
CASE 751
8
XXXXX
ALYWG
G
1
XXXXX = Specific Device Code
A = Assembly Location
L = Wafer Lot
Y = Year
W = Work Week
G = PbFree Package
ORDERING INFORMATION
See detailed ordering, marking and shipping information in the
package dimensions section on page 16 of this data sheet.
© Semiconductor Components Industries, LLC, 2013
August, 2013 Rev. 1
1
Publication Order Number:
NCP4355/D

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NCP4355A pdf
NCP4355
ELECTRICAL CHARACTERISTICS
0°C TJ 125°C; VCC = 15 V; unless otherwise noted. Typical values are at TJ = +25°C.
Parameter
Test Conditions
Symbol
Maximum Operating Input Voltage
VCC
VCC UVLO
VCC UVLO Hysteresis
Quiescent Current In Regulation
VCC rising
VCC falling
NCP4355A
NCP4355B
VCCUVLO
VCCUVLOHYS
ICC
NCP4355C
Quiescent Current In OFF mode
VOLTAGE CONTROL LOOP OTA
VSNS < 1.12 V
ICCOFF
Transconductance
Sink current only
Reference Voltage
Sink Current Capability
Inverting Input Bias Current
3.8 V VCC 36.0 V, TJ = 25°C
3.8 V VCC 36.0 V, TJ = 0 85°C
3.8 V VCC 36.0 V, TJ = 0 125°C
In regulation, VFBC > 1.5 V
In OFF mode, VFBC > 1.5 V
In regulation
Inverting Input Bias Current Threshold
In OFF mode, VSNS > 1.12 V
In OFF mode
CURRENT CONTROL LOOP OTA (except NCP4355B)
gmV
VREF
ISINKV
IBIASV
VSNSBIASTH
Transconductance
Sink current only
Reference Voltage
Sink Current Capability
VFBC > 1.5 V
Inverting Input Bias Current
ISNS = VREFC
MINIMUM VOLTAGE COMPARATOR (except NCP4355A)
gmC
VREFC
ISINKC
IBIASC
Threshold Voltage
Hysteresis
Output change from logic high to logic low
OFF MODE DETECTION COMPARATOR
VREFM
VMINH
Threshold Value
Hysteresis
LED DRIVER (except NCP4355C)
2.5 V VCC 36.0 V
VCC = 15 V
Output change from logic high to logic low
VOFFDETTH
VOFFDETH
Switching Frequency
Duty Cycle
Switch Resistance
ON MODE CONTROL
ILED = 5 mA
fSWLED
DLED
RSW2
Sink Current
In ON mode, VONOFF > 0.6 V
IDRIVEON
Min
3.75
3.22
0.4
1.244
1.240
1.230
2.5
1.2
100
2.6
1.07
60.0
2.5
100
355
1.47
10.0
140
Typ
4.00
3.50
0.5
125
107
115
90
1
1.250
1.250
1.250
1.5
2.3
1.12
3
62.5
377
40
10% VCC
1.50
40
1
12.5
50
160
Max
36.0
4.25
3.78
155
135
155
110
1.256
1.264
1.270
2.0
100
1.9
1.17
65.0
100
400
1.53
15.0
180
Unit
V
V
V
mA
mA
S
V
mA
mA
nA
mA
V
S
mV
mA
nA
mV
mV
V
V
mV
kHz
%
W
mA
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NCP4355A arduino
NCP4355
OFF mode is detected. In OFF mode SW1 is switched off
and no IONOFF current is going through ON/OFF pin. The
primary controller’s REM pin voltage increases and primary
IC goes in to off mode.
IBIASV current flow from VSNS pin to feedback divider
is also activated when OFF mode is detected. This current
increases voltage at VSNS pin and due to it voltage OTA
sinks reduced current through regulation optocoupler. OTA
stops to sink current when VSNS voltage drops below VREF.
IBIASV current disappears when VSNS voltage is lower than
90% of VREF. This feature helps to avoid primary side
switching when OFF mode is detected at secondary side and
primary side is waiting for correct information at REM pin.
Minimum Output Voltage Detection (except NCP4355A)
Minimum output voltage level defines primary controller
restart from OFF mode. It can be set by shared voltage
divider with voltage regulation loop. When VMIN voltage
drops below VREFM, OFF mode is ended and primary
controller restarts.
NCP4355A has no external adjustment and uses the
internal minimum voltage level specified by minimum
falling operation supply voltage and special load detection
circuit for faster detection of load connection (T2, R16 and
R17 at Figure 24). Principe of load connection detection is
that when load is connected, output capacitor C1 is
discharged faster than C6 capacitor by IC supply current.
Voltage across D3 increases and when there is enough
voltage to open T2 some current is injected into OFFDET
divider. Voltage at OFFDET pin goes above 10% of VCC and
OFF mode ends. This circuit can also be used with B and C
versions to dramatically speed up wakeup time from OFF
mode. If this circuit is not used, it is necessary to wait for C6
discharge below VCC UVLO falling level before the
primary controller is restarted.
LED Driver (except NCP4355C)
LED driver is active when VCC is higher than VCCMIN
and output voltage is in regulation (it is off during OFF
mode). LED driver consists of an internal power switch
controlled by PWM modulated logic signal and an external
current limiting resistor R3. LED current can be computed
by Equation 5
ILED
+
VOUT
* VF_LED
R3
(eq. 5)
PWM modulation is used to increase efficiency of LED.
Operation in OFF Mode Description
Operation waveforms in off mode and transition into OFF
mode with primary controller are shown in Figure 28.
Figure shows waveforms from the first start (1) of the
convertor. At first, primary controller charges VCC
capacitor over the VCCON level (2). When primary VCC is
over this level (3), primary controller starts to operate and
VOUT is slowly rising according to primary controller start
up ramp to nominal voltage (4). When VOUT is high enough,
VCC capacitor is charged from auxiliary winding.
Primary FB pin voltage is above regulation range until
VOUT is at set level. Once VOUT is at set level, the secondary
controller starts to sink current from optocoupler LED’s and
primary FB voltage is stabilized in regulation region. With
nominal output power (without skip mode) OFFDET pin
voltage is higher than VOFFDETTH (typically 10% of VCC).
After some time, the load current decreases to low level
(5) and primary convertor uses skip mode (6) to keep
regulation of output voltage at set level and save some
energy. The skip mode consists of few switching cycles
followed by missing ones to provide limited energy by light
load. The number of missing cycles allows regulation for
any output power.
While both C1 and C2 are discharged during the missing
cycles, C2 discharge will be faster than C1 without output
current, VOFFDET drops below VOFFDETTH and OFF mode
is detected (7). This situation is shown in Figure 27 in detail.
When OFF mode is detected, current into ONOFF pin stops
to flow (7) and voltage at primary REM pin increases over
threshold level that forces primary controller into OFF
mode. Internal pullup current IBIASV is switched on (7),
VSNS pin voltage increases (thanks to IBIASV) and voltage
amplifier sinks reduced current at time (8), when VSNS is
higher than VREF (9), to keep primary FB voltage below
switching level until REM pin voltage is high enough.
IBIASV current stops when VSNS voltage drops below 90%
of VREF.
Discharging of C1 continues (10) until output voltage
drops below level set by voltage divider at VMIN pin
(except NCP4355A where minimum VOUT is defined only
by VCC UVLO) (11). ONOFF current starts to flow,
primary REM voltage decreases and primary VCC voltage
is rising (12). Primary controller starts to operate, when
VCC voltage is enough and FB voltage is at regulation area
(13). Output capacitor C1 is recharged (14) to set voltage. If
there is still light load condition primary controller goes to
skip mode (15) again and after some time secondary
controller detects OFF mode by very light or no load
condition (16) and whole cycle is repeated.
Fast Restart From OFF Mode
The IC ends OFF mode when a load is connected to the
output and VOUT is discharged to VMIN level. There exists
another connection that allows transition to normal mode
faster without waiting some time for VOUT to discharge to
VMIN (it is necessary to use it with NCP4355A). This
schematic is shown at Figure 24 in dashed box. The basic
idea is that C6 is discharged by the IC faster than C1 by
output load in OFF mode. When an output load is applied,
capacitor C1 is discharged faster and this creates the voltage
drop at D3. When there is enough voltage at D3, T2 is
conducting and current is injected into the OFFDET divider
through R16. OFFDET voltage higher than 10% of VCC
ends OFF mode and ON/OFF current starts to flow. Primary
controller leaves OFF mode because voltage at REM pin
increase above OFF mode detection threshold.
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