NB621
8A, 25V, 600kHz Synchronous Step-Down
Converter with Integrated LDO
The Future of Analog IC Technology
DESCRIPTION
FEATURES
The NB621 is a high frequency synchronous
rectified step-down switch mode converter with
a built in internal high side power MOSFET and
integrated LDO. It offers a very compact
solution to achieve 8A continuous output
current over a wide input, load and line range.
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Current mode operation provides fast transient
response and eases loop stabilization.
Full protection features include OCP and thermal
shut down.
The NB621 requires a minimum number of
readily available standard external components
and is available in a space saving 4mm x 5mm
28-pin QFN package.
Wide 5.5V to 25V Operating Input Range
8A Output Current
Internal Low RDSON Power MOSFETs
Fixed 600kHz switching frequency
Sync from 300kHz to 2MHz External Clock
Integrated 100mA LDO
Internal Compensation
Power Good Output
Integrated Bootstrap Diode
OCP Protection and Thermal Shutdown
Output Adjustable from 0.8V to 15V
Available in 4mm x 5mm 28-pin QFN package.
APPLICATIONS
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Notebook Systems and I/O Power
Networking Systems
Digital Set Top Boxes
Personal Video Recorders
Flat Panel Television and Monitors
Distributed Power Systems
All MPS parts are lead-free and adhere to the RoHS directive. For MPS green
status, please visit MPS website under Products, Quality Assurance page.
“MPS” and “The Future of Analog IC Technology” are registered trademarks of
Monolithic Power Systems, Inc.
TYPICAL APPLICATION (FOR NOTEBOOK)
VIN
5.5-25V
BST
VIN
10uF
100nF
100K
VOUT
2.0uH
SELH
SW
VCC
1k
100K
1uF
61.9k
NB621
AAM
22K
SDRV
20K
2x47uF
82pF
20k
PGOOD
FB
ON/OFF
EN/SYNC
ON/OFF
ENLDO
REGO
LDO
SS
GND
4.7uF
22nF
NB621 Rev. 1.0
1/21/2014
www.MonolithicPower.com
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2014 MPS. All Rights Reserved.
1
NB621 – 8A, 25V, 600kHz SYNCHRONOUS STEP-DOWN CONVERTER WITH INTEGRATED LDO
ORDERING INFORMATION
Part Number*
Package
Top Marking
NB621EV
QFN28 (4mmx5mm)
N621EV
* For Tape & Reel, add suffix –Z (e.g. NB621EV–Z);
For RoHS compliant packaging, add suffix –LF (e.g. NB621EV–LF–Z).
PACKAGE REFERENCE
TOP VIEW
N/C
28
22
SELH
21
IN
19 20
IN
18
IN
N/C 6
17
IN
GND 7
16
SW 2
N/C ENLDO
24
23
EN/SYNC
SDRV 8
15
BST 1
N/C REGO LDO
27 26
25
PGOOD
SW 3
SW 4
SW 5
Exposed pad on
back side
connected to GND
10
9
11 12
N/C AGND VCC AAM
13
SS
IN
14
FB
(4)
ABSOLUTE MAXIMUM RATINGS (1)
Thermal Resistance
Supply Voltage VIN .......................................28V
VSW ......................................–0.3V to VIN + 0.3V
VBS ..................................................... VSW + 6V
IVIN(RMS) ...........................................................3A
ISW(RMS) ...........................................................3A
All Other Pins................................ –0.3V to +6V
(2)
Continuous Power Dissipation (TA=+25°C )
............................................................3.1W
Junction Temperature.............................. 150°C
Lead Temperature ................................... 260°C
Storage Temperature.............. –65°C to +150°C
Notes:
1) Exceeding these ratings may damage the device.
2) The maximum allowable power dissipation is a function of the
maximum junction temperature TJ(MAX), the junction-toambient thermal resistance θJA, and the ambient temperature
TA. The maximum allowable continuous power dissipation at
any ambient temperature is calculated by PD(MAX)=(TJ(MAX)TA)/ θJA. Exceeding the maximum allowable power dissipation
will cause excessive die temperature, and the regulator will go
into thermal shutdown. Internal thermal shutdown circuitry
protects the device from permanent damage.
3) The device is not guaranteed to function outside of its
operating conditions.
4) Measured on JESD51-7, 4-layer PCB.
Recommended Operating Conditions
θJA
θJC
4x5 QFN28..............................40.......9
°C/W
(3)
Supply Voltage VIN .......................... 5.5V to 25V
Output Voltage VOUT........................ 0.8V to 15V
Operating Junct. Temp (TJ)..... –20°C to +125°C
NB621 Rev. 1.0
1/21/2014
www.MonolithicPower.com
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2014 MPS. All Rights Reserved.
2
NB621 – 8A, 25V, 600kHz SYNCHRONOUS STEP-DOWN CONVERTER WITH INTEGRATED LDO
ELECTRICAL CHARACTERISTICS
VIN = 12V, TA = +25°C, unless otherwise noted.
Parameters
Symbol
Supply Current (Shutdown)
Supply Current (Quiescent)
(5)
High Side Switch On Resistance
Switch Leakage
(5)
Current Limit
Oscillator Frequency
IIN
IIN
HSW RDS-ON
SW LKG
ILIMIT
FSW
Fold-back Frequency
Maximum Duty Cycle
Sync Frequency Range
Feedback Voltage
Feedback Current
Soft Start Charging Current
FFB
DMAX
FSYNC
VFB
IFB
ISS
EN/SYNC Input Low Voltage
EN/SYNC Input High Voltage
VILEN
VIHEN
EN Input Current
(5)
Power Good Delay
Power
Good
Sink
Current
Capability
Power Good Leakage Current
VIN
Under
Voltage
Lockout
Threshold Rising
VIN
Under
Voltage
Lockout
Threshold Hysteresis
VCC Under Voltage Lockout
Threshold Rising
VCC Under Voltage Lockout
Threshold Hysteresis
VCC Regulator
VCC Load Regulation
NB621 Rev. 1.0
1/21/2014
Min
VENLDO = 0V
VEN = 2V, VFB = 1V
VEN = 0V, VSW = 0V
Typ
Max
Units
30
1.3
50
0
TBD
TBD
μA
mA
mΩ
μA
A
kHz
10
9.5
VFB = 0.75V
600
VFB = 100mV
VFB = 700mV
0.25
90
85
0.3
788
VFB = 800mV
VSS=0V
808
10
10
2
828
50
0.4
2
VEN = 2V
VEN = 0V
fSW
%
MHz
mV
nA
μA
V
V
ENTd-Off
PGVth-Hi
PGVth-Lo
2
0
5
0.9
0.7
μsec
VFB
VFB
PGTd
0.42
Tss
IEN
EN Turn Off Delay
Power Good Threshold Rising
Power Good Threshold Falling
Condition
μA
(6)
VPG
Sink 4mA
0.4
V
IPG_LEAK
VPG = 3.3V
10
nA
INUVVth
VENLDO=open
5.06
V
INUVHYS
VENLDO=open
450
mV
VCCUVVth
VENLDO=open
VCCUVHYS
VENLDO=open
VCC
3.8
4.5
ICC=20mA
4.0
4.2
V
880
mV
5
5
V
%
www.MonolithicPower.com
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2014 MPS. All Rights Reserved.
3
NB621 – 8A, 25V, 600kHz SYNCHRONOUS STEP-DOWN CONVERTER WITH INTEGRATED LDO
ELECTRICAL CHARACTERISTICS (continued)
VIN = 12V, TA = +25°C, unless otherwise noted.
Parameters
Symbol
(5)
LDD Switch On Resistance
LDO Output Voltage
LDO Output Current
Switch Over Threshold (Rising)
RLDO
VLDO
ILDO
VSWO
Switch Over Hysteresis
VSWO-HYS
SELH Input Low Voltage
SELH Input High Voltage
ENLDO Input Low Voltage
VILENLDO
ENLDO Input High Voltage
VIHENLDO
Thermal Shutdown
VILSELH
VIHSELH
Condition
VLDO=5V, ILDO=100mA
SELH=0V, ILDO
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