NCP81062 D

NCP81062
VR12 Compatible
Synchronous Buck MOSFET
Drivers
The NCP81062 is a high performance dual MOSFET gate driver
optimized to drive the gates of both high−side and low−side power
MOSFETs in a synchronous buck converter. It can drive up to 3 nF
load with a 25 ns propagation delay and 20 ns transition time.
Adaptive anti−cross−conduction and power saving operation
circuit can provide a low switching loss and high efficiency solution
for notebook and desktop systems. Bidirectional EN pin can provide
a fault signal to controller when the gate driver fault detect under
OVP, UVLO occur. Also, an under−voltage lockout function
guarantees the outputs are low when supply voltage is low.
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DFN8
MN SUFFIX
CASE 506BJ
Features
•
•
•
•
•
•
•
•
•
•
•
•
Faster Rise and Fall Times
Adaptive Anti−Cross−Conduction Circuit
Integrated Bootstrap Diode
Pre OV function
ZCD Detect
Floating Top Driver Accommodates Boost Voltages of up to 35 V
Output Disable Control Turns Off Both MOSFETs
Under−voltage Lockout
Power Saving Operation Under Light Load Conditions
Direct Interface to NCP6151 and Other Compatible PWM
Controllers
Thermally Enhanced Package
These are Pb−Free Devices
MARKING DIAGRAM
1
XXXXX
XXXXX
ALYWG
G
XXXXX = Specific Device Code
A
= Assembly Location
L
= Wafer Lot
Y
= Year
W
= Work Week
G
= Pb−Free Package
(Note: Microdot may be in either location)
ORDERING INFORMATION
Typical Applications
• Power Solutions for Desktop Systems
Device
Package
Shipping†
NCP81062MNTWG
DFN8
(Pb−Free)
3000 / 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, 2011
July, 2011 − Rev. 0
1
Publication Order Number:
NCP81062/D
NCP81062
BST
DRVH
1
PWM
SW
FLAG
9
EN
GND
VCC
DRVL
(Top View)
Figure 1. Pin Diagram
BST
VCC
DRVH
PWM
Logic
SW
Anti−Cross
Conduction
VCC
DRVL
EN
Fault
ZCD
Detection
UVLO
Pre−OV
Figure 2. Block Diagram
Table 1. Pin Descriptions
Pin No.
Symbol
Description
1
BST
Floating bootstrap supply pin for high side gate driver. Connect the bootstrap capacitor between this pin
and the SW pin.
2
PWM
Control input. The PWM signal has three distinctive states: Low = Low Side FET Enabled, Mid = Diode
Emulation Enabled, High = High Side FET Enabled.
3
EN
4
VCC
Power supply input. Connect a bypass capacitor (0.1 mF) from this pin to ground.
5
DRVL
Low side gate drive output. Connect to the gate of low side MOSFET.
6
GND
Bias and reference ground. All signals are referenced to this node (QFN Flag).
7
SW
8
DRVH
High side gate drive output. Connect to the gate of high side MOSFET.
9
FLAG
Thermal flag. There is no electrical connection to the IC. Connect to ground plane.
Logic input. A logic high to enable the part and a logic low to disable the part.
Switch node. Connect this pin to the source of the high side MOSFET and drain of the low side MOSFET.
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NCP81062
12V_POWER
TP1
R164
R1
1.02
R143
0.0
TP4
PWM
C4
TP2
0.0
NCP81062 TP3
BST
EN
C2
4.7uF
TP5
+
CE9
390uF
VCCP
L
VREG_SW1_OUT
235nH
GND
TP6
TP7
Q9
NTMFS4851N
VREG_SW1_LG
LG
Q10
NTMFS4851N
R3
2.2
JP13_ETCH CSN11
PAD
TP8
C5
1uF
C3
4.7uF
0.0
VREG_SW1_HG
HG
VCC
C1
4.7uF
R142
PWM SW
DRON
Q1
NTMFS4821N
0.027uF
C6
2700pF
JP14_ETCH CSP11
Figure 3. Application Circuit
Table 2. ABSOLUTE MAXIMUM RATINGS
Pin Symbol
Pin Name
VMAX
VMIN
VCC
Main Supply Voltage Input
15 V
−0.3 V
BST
Bootstrap Supply Voltage
35 V wrt/ GND
40 V ≤ 50 ns wrt/ GND
15 V wrt/ SW
−0.3 V wrt/SW
SW
Switching Node
(Bootstrap Supply Return)
35 V
40 V ≤ 50 ns
−5 V
−10 V (200 ns)
DRVH
High Side Driver Output
BST+0.3 V
−0.3 V wrt/SW
−2 V (<200 ns) wrt/SW
DRVL
Low Side Driver Output
VCC+0.3 V
−0.3 V DC
−5 V (<200 ns)
PWM
DRVH and DRVL Control Input
6.5 V
−0.3 V
EN
Enable Pin
6.5 V
−0.3 V
GND
Ground
0V
0V
Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the
Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect
device reliability.
Table 3. THERMAL INFORMATION (All signals referenced to AGND unless noted otherwise)
Symbol
RqJA
Parameter
Thermal Characteristic
DFN Package (Note 1)
Value
Unit
55
°C/W
0 to 150
°C
TJ
Operating Junction Temperature Range (Note 2)
TA
Operating Ambient Temperature Range
−10 to +125
°C
TSTG
Maximum Storage Temperature Range
−55 to +150
°C
MSL
Moisture Sensitivity Level
DFN Package
* The maximum package power dissipation must be observed.
1. I in2 Cu, 1 oz thickness.
2. Operation at −40°C to 0°C guaranteed by design, not production tested.
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1
NCP81062
Table 4. ELECTRICAL CHARACTERISTICS (Unless otherwise stated: −10°C < TA < +125°C; 4.5 V < VCC < 13.2 V,
4.5 V < BST−SWN < 13.2 V, 4.5 V < BST < 30 V, 0 V < SWN < 21 V)
Parameter
Test Conditions
Min.
Typ.
Max.
Units
13.2
V
3.2
V
SUPPLY VOLTAGE
4.5
VCC Operation Voltage
Power ON Reset Threshold
2.75
UNDERVOLTAGE LOCKOUT
VCC Start Threshold
3.8
4.35
4.5
V
VCC UVLO Hysteresis
150
200
250
mV
2.1
2.25
2.4
V
Output Overvoltage Trip Threshold at
Startup
Power Startup time, VCC > POR
SUPPLY CURRENT
Normal Mode
Icc + Ibst, EN = 5 V, PWM = OSC, Fsw = 100 KHz,
Cload = 3 nF for DRVH, 3 nF for DRVL
12.2
mA
Standby Current
Icc + Ibst, EN = GND
0.5
Standby Current
ICC + IBST, EN = HIGH, PWM = LOW,
No loading on DRVH & DRVL
2.1
mA
Standby Current
ICC + IBST, EN = HIGH, PWM = HIGH,
No loading on DRVH & DRVL
2.2
mA
1.9
mA
BOOTSTRAP DIODE
Forward Voltage
VCC = 12 V, forward bias current = 2 mA
0.1
0.4
0.6
V
PWM INPUT
PWM Input High
3.4
PWM Mid−State
1.3
V
PWM Input Low
ZCD Blanking Timer
2.7
V
0.7
V
250
ns
HIGH SIDE DRIVER (VCC = 12 V)
Output Impedance, Sourcing Current
VBST − VSW = 12 V
2.0
3.5
W
Output Impedance, Sinking Current
VBST − VSW = 12 V
1.0
2.0
W
DRVH Rise Time trDRVH
VVCC = 12 V, 3 nF load, VBST−VSW = 12 V
16
30
ns
DRVH Fall Time tfDRVH
VVCC = 12 V, 3 nF load, VBST−VSW = 12 V
11
25
ns
DRVH Turn−Off Propagation Delay
tpdhDRVH
CLOAD = 3 nF
30
ns
DRVH Turn−On Propagation Delay
tpdlDRVH
CLOAD = 3 nF
30
ns
SW Pull Down Resistance
SW to PGND
45
kW
DRVH Pull Down Resistance
DRVH to SW, BST−SW = 0 V
45
kW
Output Impedance, Sourcing Current
VBST − VSW = 5 V
4.5
W
Output Impedance, Sinking Current
VBST − VSW = 5 V
2.9
W
DRVH Rise Time trDRVH
VVCC = 5 V, 3 nF load, VBST − VSW = 5 V
30
ns
DRVH Fall Time tfDRVH
VVCC = 5 V, 3 nF load, VBST − VSW = 5 V
27
ns
DRVH Turn−Off Propagation Delay
tpdhDRVH
CLOAD = 3 nF
20
ns
DRVH Turn−On Propagation Delay
tpdlDRVH
CLOAD = 3 nF
27
ns
SW Pull Down Resistance
SW to PGND
45
kW
8.0
HIGH SIDE DRIVER (VCC = 5 V)
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NCP81062
Table 4. ELECTRICAL CHARACTERISTICS (Unless otherwise stated: −10°C < TA < +125°C; 4.5 V < VCC < 13.2 V,
4.5 V < BST−SWN < 13.2 V, 4.5 V < BST < 30 V, 0 V < SWN < 21 V)
Parameter
Test Conditions
Min.
Typ.
Max.
Units
HIGH SIDE DRIVER (VCC = 5 V)
DRVH Pull Down Resistance
DRVH to SW, BST−SW = 0 V
45
kW
LOW SIDE DRIVER (VCC = 12 V)
Output Impedance, Sourcing Current
2.0
3.5
W
0.8
1.8
W
DRVL Rise Time trDRVL
CLOAD = 3 nF
16
35
ns
DRVL Fall Time tfDRVL
CLOAD = 3 nF
11
20
ns
DRVL Turn−Off Propagation Delay
tpdlDRVL
CLOAD = 3 nF
35
ns
DRVL Turn−On Propagation Delay
tpdhDRVL
CLOAD = 3 nF
30
ns
DRVL Pull Down Resistance
DRVL to PGND, VCC = PGND
Output Impedance, Sinking Current
8.0
45
kW
Output Impedance, Sourcing Current
4.5
W
Output Impedance, Sinking Current
2.4
W
LOW SIDE DRIVER (VCC = 5 V)
DRVL Rise Time trDRVL
CLOAD = 3 nF
30
ns
DRVL Fall Time tfDRVL
CLOAD = 3 nF
22
ns
DRVL Turn−Off Propagation Delay
tpdlDRVL
CLOAD = 3 nF
27
ns
DRVL Turn−On Propagation Delay
tpdhDRVL
CLOAD = 3 nF
12
ns
DRVL Pull Down Resistance
DRVL to PGND, VCC = PGND
45
kW
EN INPUT
Input Voltage High
2.0
V
Input Voltage Low
1.0
Hysteresis
V
500
mV
Normal Mode Bias Current
−1
1
mA
Enable Pin Sink Current
4
30
mA
40
ns
Propagation Delay Time
20
SW Node
SW Node Leakage Current
Zero Cross Detection Threshold Voltage
mA
20
SW to −20 mV, ramp slowly until BG goes off
(Start in DCM mode) (Note 3)
−6
mV
Table 5. DECODER TRUTH TABLE
PWM INPUT
ZCD
DRVL
DRVH
PWM High
ZCD Reset
Low
High
PWM Mid
Positive current through the inductor
High
Low
PWM Mid
Zero current through the inductor
Low
Low
PWM Low
ZCD Reset
High
Low
3. Guaranteed by design; not production tested.
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NCP81062
1V
1V
Figure 4.
PWM
DRVH−SW
DRVL
IL
Figure 5. Timing Diagram
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NCP81062
APPLICATIONS INFORMATION
The NCP81062 gate driver is a single phase MOSFET
driver designed for driving N−channel MOSFETs in a
synchronous buck converter topology. The NCP81062 is
designed to work with ON Semiconductor’s NCP6131
multi−phase controller. This gate driver is optimized for
desktop applications.
turn on of the high–side MOSFET. When the PWM pull
low, gate DRVH will go low after the propagation delay
(tpd DRVH).
The time to turn off the high side MOSFET is depending
on the total gate charge of the high−side MOSFET. A timer
will be triggered once the high side MOSFET is turn off to
delay the turn on the low−side MOSFET.
Undervoltage Lockout
The DRVH and DRVL are held low until VCC reaches
4.5 V during startup. The PWM signals will control the gate
status when VCC threshold is exceeded. If VCC decreases to
250 mV below the threshold, the output gate will be forced
low until input voltage VCC rises above the startup threshold.
Low−Side Driver Timeout
In normal operation, the DRVH signal tracks the PWM
signal and turns off the Q1 high−side switch with a few 10
ns delay (tpdlDRVH) following the falling edge of the input
signal. When Q1is turned off, DRVL is allowed to go high,
Q2 turns on, and the SW node voltage collapses to zero. But
in a fault condition such as a high−side Q1 switch
drain−source short circuit, the SW node cannot fall to zero,
even when DRVH goes low. This driver has a timer circuit
to address this scenario. Every time the PWM goes low, a
DRVL on−time delay timer is triggered.
If the SW node voltage does not trigger a low−side
turn−on, the DRVL on−time delay circuit does it instead,
when it times out with tSW(TO) delay. If Q1 is still turned on,
that is, its drain is shorted to the source, Q2 turns on and
creates a direct short circuit across the VDCIN voltage rail.
The crowbar action causes the fuse in the VDCIN current
path to open. The opening of the fuse saves the load (CPU)
from potential damage that the high−side switch short
circuit could have caused.
Power−On Reset
Power−On Reset feature is used to protect a gate driver
avoid abnormal status driving the startup condition. When
the initial soft−start voltage is higher than 2.75 V, the gate
driver will monitor the switching node SW pin. If SW pin
high than 2.25 V, bottom gate will be force to high for
discharge the output capacitor. The fault mode will be latch
and EN pin will force to be low, unless the driver is recycle.
When input voltage is higher than 4.5 V, and EN goes high,
the gate driver will normal operation, top gate driver
DRVH and bottom gate driver will follow the PWM signal
decode to a status.
Bi−directional EN Signal
Fault modes such as Power−On Reset and Undervoltage
Lockout will de−assert the EN pin, which will pull down
the DRON pin of controller as well. Thus the controller will
be shut down consequently.
Layout Guidelines
Layout for DC−DC converter is very important. The
bootstrap and VCC bypass capacitors should be placed as
close as to the driver IC.
Connect GND pin to local ground plane. The ground
plane can provide a good return path for gate drives and
reduce the ground noise. The thermal slug should be tied to
the ground plane for good heat dissipation. To minimize the
ground loop for low side MOSFET, the driver GND pin
should be close to the low−side MOSFET source pin. The
gate drive trace should be routed to minimize the length,
the minimum width is 20 mils.
PWM Input and Zero Cross Detect (ZCD)
The PWM input, along with EN and ZCD, control the
state of DRVH and DRVL.
When PWM is set high, DRVH will be set high after the
adaptive non−overlap delay. When PWM is set low, DRVL
will be set high after the adaptive non−overlap delay.
When the PWM is set to the mid state, DRVH will be set
low, and after the adaptive non−overlap delay, DRVL will
be set high. DRVL remains high during the ZCD blanking
time. When the timer is expired, the SW pin will be
monitored for zero cross detection. After the detection, the
DRVL will be set low.
Gate Driver Power Loss Calculation
The gate driver power loss consists of the gate drive loss
and quiescent power loss.
The equation below can be used to calculate the power
dissipation of the gate driver. Where QGMF is the total gate
charge for each main MOSFET and QGSF is the total gate
charge for each synchronous MOSFET.
Adaptive Nonoverlap
The nonoverlap dead time control is used to avoid the
shoot through damage the power MOSFETs. When the
PWM signal pull high, DRVL will go low after a
propagation delay, the controller will monitors the
switching node (SWN) pin voltage and the gate voltage of
the MOSFET to know the status of the MOSFET. When the
low side MOSFET status is off an internal timer will delay
PDRV + [
2
fSW
n
ǒn MF
QGMF ) n SF
QGSFǓ ) ICC]
VCC
Also shown is the standby dissipation factor (ICC ⋅ VCC)
of the driver.
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NCP81062
PACKAGE DIMENSIONS
DFN8 3x3, 0.5P
CASE 506BJ−01
ISSUE O
PIN 1
REFERENCE
2X
0.10 C
2X
NOTES:
1. DIMENSIONS AND TOLERANCING PER ASME
Y14.5M, 1994.
2. CONTROLLING DIMENSION: MILLIMETERS.
3. DIMENSION b APPLIES TO PLATED TERMINAL
AND IS MEASURED BETWEEN 0.15 AND 0.30
MM FROM TERMINAL.
4. COPLANARITY APPLIES TO THE EXPOSED
PAD AS WELL AS THE TERMINALS.
L
L1
ÇÇÇ
ÇÇÇ
ÇÇÇ
0.10 C
EDGE OF PACKAGE
A
B
D
DETAIL A
E
OPTIONAL
CONSTRUCTION
DIM
A
A1
A3
b
D
D2
E
E2
e
K
L
L1
L
TOP VIEW
DETAIL A
OPTIONAL
CONSTRUCTION
DETAIL B
0.05 C
A
8X
0.05 C
(A3)
NOTE 4
SIDE VIEW
D2
8X
L
8X
K
1
C
A1
SOLDERMASK DEFINED
MOUNTING FOOTPRINT
SEATING
PLANE
1.85
DETAIL A
EXPOSED Cu
4
E2
ÉÉ
ÉÉ
MOLD CMPD
5
e
8X
8X
0.35
DETAIL B
OPTIONAL
CONSTRUCTION
8
MILLIMETERS
MIN
MAX
0.80
1.00
0.00
0.05
0.20 REF
0.18
0.30
3.00 BSC
1.64
1.84
3.00 BSC
1.35
1.55
0.50 BSC
0.20
−−−
0.30
0.50
0.00
0.03
3.30
1.55
0.63
0.50
PITCH
b
0.10 C A B
BOTTOM VIEW
0.05 C
NOTE 3
8X
DIMENSION: MILLIMETERS
*For additional information on our Pb−Free strategy and soldering
details, please download the ON Semiconductor Soldering and
Mounting Techniques Reference Manual, SOLDERRM/D.
ON Semiconductor and
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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
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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
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NCP81062/D