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PDF NCP81278 Data sheet ( Hoja de datos )
| Número de pieza | NCP81278 | |
| Descripción | Compact 2-Phase Synchronous Buck Controller | |
| Fabricantes | ON Semiconductor | |
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NCP81278
Compact 2-Phase
Synchronous Buck
Controller with Integrated
Gate Drivers and PWM VID
Interface
The NCP81278, a general−purpose two−phase synchronous buck
controller, integrates gate drivers and PWM VID interface in a
QFN−20 package and provides a compact−footprint power
management solution for new generation computing processors. It has
a programmable power save interface (PSI) and is able to operate in
1−phase diode emulation mode to obtain high efficiency in light−load
condition. Operating in high switching frequency up to 800 kHz
allows employing small size inductor and capacitors. The part is able
to support all−ceramic−capacitor applications.
Features
• 3.6 V to 24 V Input Voltage Range
• Output Voltage up to 2.0 V with PWM VID Interface
• Differential Output Voltage Sense
• Integrated Gate Drivers
• 200 kHz ~ 800 kHz Switching Frequency
• Power Saving Interface (PSI)
• Support both 3.3 V and 1.8 V VID
• Power Good Output
• Programmable Over Current Protection
• Over Voltage Protection
• Under Voltage Protection
• Thermal Shutdown Protection
• QFN20, 3x3 mm, 0.4 mm Pitch Package
Typical Applications
• GPU and CPU Power
• Graphics Card Applications
• Desktop and Notebook Applications
www.onsemi.com
QFN20
CASE 485BC
MARKING DIAGRAM
81278
ALYWG
G
81278
A
L
Y
W
G
= Specific Device Code
= Assembly Location
= Wafer Lot
= Year
= Work Week
= Pb−Free Package
(Note: Microdot may be in either location)
PIN CONNECTIONS
BST1
HG1
EN
PSI
VID
1
GND
BST2
HG2
PGOOD
COMP/ILMT
FB
(Top View)
ORDERING INFORMATION
Device
NCP81278MNTXG
Package
QFN20
(Pb−Free)
Shipping†
4,000 /
Tape & Reel
†For information on tape and reel specifications,
including part orientation and tape sizes, please
refer to our Tape and Reel Packaging Specification
Brochure, BRD8011/D.
© Semiconductor Components Industries, LLC, 2016
May, 2016 − Rev. 3
1
Publication Order Number:
NCP81278/D
1 page  
NCP81278
MAXIMUM RATINGS
Value
PH to GND
Rating
Symbol
VPH
Min
−2
−8 (<100 ns)
Max
30
Unit
V
Supply Voltage PVCC to GND
BST to GND
BST to PH
HG to PH
VPVCC
VBST_GND
VBST_PH
VHG
−0.3
−0.3
−0.3
−0.3
−2 (<200 ns)
6.5
35
6.5
BST+0.3
V
V
V
V
LG to GND
VLG
−0.3 MIN (PVCC+0.3, 6.5)
V
−2 (<200 ns)
FBRTN to GND
Other Pins to GND
VFBRTN
−0.3 0.3
−0.3 MIN (VCC+0.3, 6.5)
V
V
Human Body Model (HBM) ESD Rating are (Note 1)
ESD HBM
2000
V
Machine Model (MM) ESD Rating are (Note 1)
ESD MM
200 V
Latch up Current: (Note 2)
All pins, except digital pins
Digital pins
ILU mA
−100
100
−10 10
Operating Junction Temperature Range (Notes 3 and 4)
Operating Ambient Temperature Range
Storage Temperature Range
Thermal Resistance Junction to Top Case (Note 5)
Thermal Resistance Junction to Board (Note 5)
Thermal Resistance Junction to Ambient (Note 4)
Power Dissipation (Note 6)
Moisture Sensitivity Level (Note 7)
TJ
TA
TSTG
RΨJC
RΨJB
RθJA
PD
MSL
−40 125
−40 100
−40 150
5
4
40
2.5
1
°C
°C
°C
°C/W
°C/W
°C/W
W
−
Stresses exceeding those listed in the Maximum Ratings table may damage the device. If any of these limits are exceeded, device functionality
should not be assumed, damage may occur and reliability may be affected.
1. This device is ESD sensitive. Handling precautions are needed to avoid damage or performance degradation.
2. Latch up Current per JEDEC standard: JESD78 class II.
3. The thermal shutdown set to 150°C (typical) avoids potential irreversible damage on the device due to power dissipation.
4. JEDEC standard JESD 51−7 (1S2P Direct−Attach Method) with 0 LFM.
5. JEDEC standard JESD 51−7 (1S2P Direct−Attach Method) with 0 LFM. It is for checking junction temperature using external measurement.
6. The maximum power dissipation (PD) is dependent on input voltage, maximum output current and external components selected. Tambient
= 25°C, Tjunc_max = 125°C, PD = (Tjunc_max−T_amb)/Theta JA.
7. Moisture Sensitivity Level (MSL): 1 per IPC/JEDEC standard: J−STD−020A.
www.onsemi.com
5
5 Page 
NCP81278
Soft Start
The NCP81278 has a soft start function. The output starts
to ramp up following a system reset period after the device
is enabled. The device is able to start up smoothly under an
output pre−biased condition without discharging the output
before ramping up.
REFIN Discharge
An internal switch in REFIN pin starts to short REFIN to
GND just after EN is pulled high and it turns off just before
the beginning of the soft start. The typical on resistance of
the switch is 6.91 W.
Output Discharge in Shut Down
The NCP81278 has an output discharge function when the
device is in shutdown mode. The resistors (5 kW per phase)
from PH node to GND in both phases are active to discharge
the output capacitors.
Over Current Protection
The NCP81278 protects converters from over current.
The current through each phase is monitored by voltage
sensing from phase node PHx to GND pin. The sense signal
is compared to an internal voltage threshold. Once over load
happens, the inductor current is limited to an average current
per phase, which can be estimated by
ILMT(phase)
+
VthOC
RDS(phase)
(eq. 3)
where RDS(phase) is a total on conduction resistance of
low−side MOSFETs per phase. Normally, a continuous over
load event leads to a voltage drop in the output voltage and
possible to eventually trip under voltage protection.
The over−current threshold can be externally
programmed by adding a 1% tolerance resistor between
COMP pin and GND. The selectable thresholds can be
found in the electrical table. To assure accurate resistance
detection, the total capacitance from COMP pin to FB pin
should be less than 330 pF.
Under Voltage Protection
There are two under voltage protections implemented in
the NCP81278, which are fast under voltage protection and
slow under voltage protection.
Fast under voltage protection (FUVP) protects converters
in case of an extreme short circuit in output by monitoring
FB voltage. Once FB voltage drops below 0.2 V for more
than 1 ms, the NCP81278 latches off, both the high−side
MOSFETs and the low−side MOSFETs in all phases are
turned off. The fault remains set until the system has either
VCC or EN toggled state. The FUVP function is disabled in
soft start.
Slow under voltage protection (SUVP) of the NCP81278
is based on voltage detection at COMP pin. In normal
operation, COMP level is below 2.5 V. When the output
voltage drops below REFIN voltage for long time and
COMP rises to be over 3 V, an internal UV fault timer will
be triggered. If the fault still exists after 50 ms, the
NCP81278 latches off, both the high−side MOSFETs and
the low−side MOSFETs in all phases are turned off. The
fault remains set until the system has either VCC or EN
toggled state.
Over Voltage Protection
Over voltage protection of the NCP81278 is based on
voltage detection at FB pin. Once FB voltage is over 2 V for
more than 1 ms, all the high−side MOSFETs are turned off
and all the low−side MOSFETs are latched on. The
NCP81278 latches off until the system has either VCC or EN
has toggled state.
Thermal Shutdown
The NCP81278 has a thermal shutdown protection to
protect the device from overheating when the die
temperature exceeds 150°C. Once the thermal protection is
triggered, the fault state can be ended by re−applying VCC
and/or EN if the temperature drops down below 125°C.
www.onsemi.com
11
11 Page | ||
| Páginas | Total 13 Páginas | |
| PDF Descargar | [ Datasheet NCP81278.PDF ] | |
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