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NCP43080ADR2G

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NCP43080
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13
TYPICAL CHARACTERISTICS
Figure 32. Driver and Output Voltage, ver. B, D
and Q
Figure 33. Driver Output Voltage, ver. A and C
T
J
(°C) T
J
(°C)
100806040200−20−40
9.0
9.2
9.4
9.6
9.8
10.0
10.2
10.4
100806040200−20−40
4.3
4.5
4.7
4.9
5.1
5.3
5.5
Figure 34. Maximum On−time, ver. Q Figure 35. Maximum On−time, V
MAX_TON
= 3 V,
ver. Q
V
MAX_TON
(V) T
J
(°C)
3.02.52.01.51.00.50
0
5
15
20
25
35
45
50
100806040200−20−40
4.3
4.4
4.6
4.7
4.8
5.0
5.1
5.3
Figure 36. Maximum On−time, V
MAX_TON
=
0.3 V, ver. Q
T
J
(°C)
100806040200−20−40
41
43
45
47
49
51
53
55
V
DRV
(V)
V
DRV
(V)
t
MAX_TON
(ms)
t
MAX_TON
(ms)
t
MAX_TON
(ms)
120
V
CC
= 12 V, C
DRV
= 0 nF
V
CC
= 12 V, C
DRV
= 1 nF
V
CC
= 12 V, C
DRV
= 10 nF
V
CC
= 35 V, C
DRV
= 0 nF
V
CC
= 35 V, C
DRV
= 1 nF
V
CC
= 35 V, C
DRV
= 10 nF
V
CC
= 12 V, C
DRV
= 0 nF
V
CC
= 12 V, C
DRV
= 1 nF
V
CC
= 12 V, C
DRV
= 10 nF
V
CC
= 35 V, C
DRV
= 0 nF
V
CC
= 35 V, C
DRV
= 1 nF
V
CC
= 35 V, C
DRV
= 10 nF
120
T
J
= 125°C
T
J
= 85°C
T
J
= 55°C
T
J
= 25°C
T
J
= 0°C
T
J
= −20°C
T
J
= −40°C
10
30
40
120
4.5
4.9
5.2
120
NCP43080
www.onsemi.com
14
APPLICATION INFORMATION
General description
The NCP43080 is designed to operate either as a
standalone IC or as a companion IC to a primary side
controller to help achieve efficient synchronous
rectification in switch mode power supplies. This controller
features a high current gate driver along with high−speed
logic circuitry to provide appropriately timed drive signals
to a synchronous rectification MOSFET. With its novel
architecture, the NCP43080 has enough versatility to keep
the synchronous rectification system efficient under any
operating mode.
The NCP43080 works from an available voltage with
range from 4 V (A, D & Q options) or 8 V (B & C options)
to 35 V (typical). The wide V
CC
range allows direct
connection to the SMPS output voltage of most adapters
such as notebooks, cell phone chargers and LCD TV
adapters.
Precise turn-off threshold of the current sense comparator
together with an accurate offset current source allows the
user to adjust for any required turn-off current threshold of
the SR MOSFET switch using a single resistor. Compared
to other SR controllers that provide turn-off thresholds in the
range of −10 mV to −5 mV, the NCP43080 offers a turn-off
threshold of 0 mV. When using a low R
DS(on)
SR (1 mW)
MOSFET our competition, with a −10 mV turn off, will turn
off with 10 A still flowing through the SR FET, while our
0 mV turn off turns off the FET at 0 A; significantly
reducing the turn-off current threshold and improving
efficiency. Many of the competitor parts maintain a drain
source voltage across the MOSFET causing the SR
MOSFET to operate in the linear region to reduce turn−off
time. Thanks to the 8 A sink current of the NCP43080
significantly reduces turn off time allowing for a minimal
drain source voltage to be utilized and efficiency
maximized.
To overcome false triggering issues after turn-on and
turn−off events, the NCP43080 provides adjustable
minimum on-time and off-time blanking periods. Blanking
times can be adjusted independently of IC VCC using
external resistors connected to GND. If needed, blanking
periods can be modulated using additional components.
An extremely fast turn−off comparator, implemented on
the current sense pin, allows for NCP43080 implementation
in CCM applications without any additional components or
external triggering.
An output driver features capability to keep SR transistor
closed even when there is no supply voltage for NCP43080.
SR transistor drain voltage goes up and down during SMPS
operation and this is transferred through drain gate
capacitance to gate and may turn on transistor. NCP43080
uses this pulsing voltage at SR transistor gate (DRV pin) and
uses it internally to provide enough supply to activate
internal driver sink transistor. DRV voltage is pulled low
(not to zero) thanks to this feature and eliminate the risk of
turned on SR transistor before enough V
CC
is applied to
NCP43080.
Some IC versions include a MAX_TON circuit that helps
a quasi resonant (QR) controller to work in CCM mode
when a heavy load is present like in the example of a
printer’s motor starting up.
Finally, the NCP43080 features a special pin (LLD) that
can be used to reduce gate driver voltage clamp according
to application load conditions. This feature helps to reduce
issues with transition from disabled driver to full driver
output voltage and back. Disable state can be also activated
through this pin to decrease power consumption in no load
conditions. If the LLD feature is not wanted then the LLD
pin can be tied to GND.
Current Sense Input
Figure 37 shows the internal connection of the CS
circuitry on the current sense input. When the voltage on the
secondary winding of the SMPS reverses, the body diode of
M1 starts to conduct current and the voltage of M1’s drain
drops approximately to −1 V. The CS pin sources current of
100 mA that creates a voltage drop on the R
SHIFT_CS
resistor
(resistor is optional, we recommend shorting this resistor).
Once the voltage on the CS pin is lower than V
TH_CS_ON
threshold, M1 is turned−on. Because of parasitic
impedances, significant ringing can occur in the application.
To overcome false sudden turn−off due to mentioned
ringing, the minimum conduction time of the SR MOSFET
is activated. Minimum conduction time can be adjusted
using the R
MIN_TON
resistor.
NCP43080
www.onsemi.com
15
Figure 37. Current Sensing Circuitry Functionality
The SR MOSFET is turned-off as soon as the voltage on
the CS pin is higher than V
TH_CS_OFF
(typically −0.5 mV
minus any voltage dropped on the optional R
SHIFT_CS
). For
the same ringing reason, a minimum off-time timer is
asserted once the V
CS
goes above V
TH_CS_RESET
. The
minimum off-time can be externally adjusted using
R
MIN_TOFF
resistor. The minimum off−time generator can
be re−triggered by MIN_TOFF reset comparator if some
spurious ringing occurs on the CS input after SR MOSFET
turn−off event. This feature significantly simplifies SR
system implementation in flyback converters.
In an LLC converter the SR MOSFET M1 channel
conducts while secondary side current is decreasing (refer to
Figure 38). Therefore the turn−off current depends on
MOSFET R
DSON
. The −0.5 mV threshold provides an
optimum switching period usage while keeping enough time
margin for the gate turn-off. The R
SHIFT_CS
resistor
provides the designer with the possibility to modify
(increase) the actual turn−on and turn−off secondary current
thresholds. To ensure proper switching, the min_t
OFF
timer
is reset, when the V
DS
of the MOSFET rings and falls down
past the V
TH_CS_RESET
. The minimum off−time needs to
expire before another drive pulse can be initiated. Minimum
off−time timer is started again when V
DS
rises above
V
TH_CS_RESET
.
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NCP43080ADR2G

Mfr. #:
Buy NCP43080ADR2G
Manufacturer:
ON Semiconductor
Description:
Switching Controllers SYNC-RECTIFIER CONTROLLER
Lifecycle:
New from this manufacturer.
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