NB621
8A, 25V, 600kHz Synchronous Step-Down
Converter with Integrated LDO
The Future of Analog IC Technology
DESCRIPTION
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.
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.
FEATURES
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Wide 5.5V to 25V Operating Input Range
8A Output Current
Internal Low R
DSON
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.
Notebook Systems and I/O Power
Networking Systems
Digital Set Top Boxes
Personal Video Recorders
Flat Panel Television and Monitors
Distributed Power Systems
APPLICATIONS
“MPS” and “The Future of Analog IC Technology” are Registered Trademarks of
Monolithic Power Systems, Inc.
TYPICAL APPLICATION (FOR NOTEBOOK)
VIN
U1
NB621EV
17,18,19,20,21
IN
BST
1
VCC
GND
VCC
R14
10k
VCC
R3
100k
AAM
PGOOD
EN
R4
60.4k
R5
20k
R2
100k
R1
100k
11
VCC
SW
FB
2,3,4,5
14
8
R9
22k
Q1
FDS6670AS
R11
61.9k
3.3V
VOUT
GND
12
15
16
AAM
PGOOD
EN/SYNC
SDRV
REGO 26
LDO
25
6,9,24,27,28
R13
1k
23 ENLDO
NC
SS GND SELH
7,10
13
22
R12
20.0k
R8
VIN
ENLDO
100k
NB621 Rev. 0.9
12/10/2013
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2013 MPS. All Rights Reserved.
1
NB621 – 8A, 25V, 600kHz SYNCHRONOUS STEP-DOWN CONVERTER WITH INTEGRATED LDO
ORDERING INFORMATION
Part Number*
NB621EV
Package
QFN28 (4mmx5mm)
Top Marking
N621EV
Free Air Temperature (T
A
)
–20°C to +85°C
*
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
BST
1
SW
2
SW
3
SW
4
SW
5
N/C
6
GND
7
SDRV
8
10
9
11 12
N/C AGND VCC AAM
13
SS
14
FB
Exposed pad on
back side
connected to GND
N/C REGO LDO
27 26
25
N/C ENLDO
24
23
22
21
19 20
18
17
16
15
SELH
IN
IN
IN
IN
IN
EN/SYNC
PGOOD
ABSOLUTE MAXIMUM RATINGS
(1)
Supply Voltage V
IN
.......................................28V
V
SW
......................................–0.3V to V
IN
+ 0.3V
V
BS
..................................................... V
SW
+ 6V
I
VIN(RMS)
...........................................................3A
I
SW(RMS)
...........................................................3A
All Other Pins................................ –0.3V to +6V
(2)
Continuous Power Dissipation (T
A
=+25°C )
............................................................3.1W
Junction Temperature.............................. 150°C
Lead Temperature ................................... 260°C
Storage Temperature.............. –65°C to +150°C
Thermal Resistance
(4)
θ
JA
θ
JC
4x5 QFN28..............................40.......9
°C/W
Notes:
1) Exceeding these ratings may damage the device.
2) The maximum allowable power dissipation is a function of the
maximum junction temperature T
J
(MAX), the junction-to-
ambient thermal resistance
θ
JA
, and the ambient temperature
T
A
. The maximum allowable continuous power dissipation at
any ambient temperature is calculated by P
D
(MAX)=(T
J
(MAX)-
T
A
)/
θ
JA
. 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
(3)
Supply Voltage V
IN
.......................... 5.5V to 25V
Output Voltage V
OUT
........................ 0.8V to 15V
Operating Junct. Temp (T
J
)..... –20°C to +125°C
NB621 Rev. 0.9
12/10/2013
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2013 MPS. All Rights Reserved.
2
NB621 – 8A, 25V, 600kHz SYNCHRONOUS STEP-DOWN CONVERTER WITH INTEGRATED LDO
ELECTRICAL CHARACTERISTICS
V
IN
= 12V, T
A
= +25°C, unless otherwise noted.
Parameters
Supply Current (Shutdown)
Supply Current (Quiescent)
(5)
High Side Switch On Resistance
Switch Leakage
(5)
Current Limit
Oscillator Frequency
Fold-back Frequency
Maximum Duty Cycle
Sync Frequency Range
Feedback Voltage
Feedback Current
Soft Start Charging Current
EN/SYNC Input Low Voltage
EN/SYNC Input High Voltage
EN Input Current
EN Turn Off Delay
Power Good Threshold Rising
Power Good Threshold Falling
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
(5)
Symbol
I
IN
I
IN
HSW
RDS-ON
SW
LKG
I
LIMIT
F
SW
F
FB
D
MAX
F
SYNC
V
FB
I
FB
I
SS
VIL
EN
VIH
EN
I
EN
EN
Td-Off
PG
Vth-Hi
PG
Vth-Lo
PG
Td
V
PG
I
PG_LEAK
INUV
Vth
INUV
HYS
VCCUV
Vth
VCCUV
HYS
V
CC
Condition
V
ENLDO
=
0V
V
EN
=
2V, V
FB
= 1V
V
EN
= 0V, V
SW
= 0V
Min
Typ
30
1.3
50
0
Max
TBD
TBD
10
Units
μA
mA
mΩ
μA
A
kHz
f
SW
%
MHz
mV
nA
μA
V
V
μA
μsec
V
FB
V
FB
Tss
(6)
9.5
V
FB
= 0.75V
V
FB
= 100mV
V
FB
= 700mV
85
0.3
788
600
0.25
90
808
10
10
2
828
50
0.4
2
V
EN
= 2V
V
EN
= 0V
2
0
5
0.9
0.7
0.42
Sink 4mA
V
PG
= 3.3V
V
ENLDO
=open
V
ENLDO
=open
V
ENLDO
=open
V
ENLDO
=open
4.5
I
CC
=20mA
3.8
5.06
450
4.0
880
5
5
4.2
0.4
10
V
FB
= 800mV
V
SS
=0V
V
nA
V
mV
V
mV
V
%
NB621 Rev. 0.9
12/10/2013
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2013 MPS. All Rights Reserved.
3
NB621 – 8A, 25V, 600kHz SYNCHRONOUS STEP-DOWN CONVERTER WITH INTEGRATED LDO
ELECTRICAL CHARACTERISTICS
(continued)
V
IN
= 12V, T
A
= +25°C, unless otherwise noted.
Parameters
LDD Switch On Resistance
(5)
Symbol
R
LDO
Condition
V
LDO
=5V, I
LDO
=100mA
SELH=0V, I
LDO
<100mA
SELH=0V, I
LDO
<100mA,
6.5V<V
IN
<25V
V
LDO
=0V, I
LDO
<50mA,
5.5V<V
IN
<25V
SELH=5V, I
LDO
<100mA
SELH=5V, I
LDO
<100mA,
6.5V<V
IN
<25V
SELH=5V, I
LDO
<50mA,
5.5V<V
IN
<25V
SELH=0V
SELH=5V
SELH=0V
SELH=5V
SELH=0V
SELH=5V
Min
4.8
4.75
4.75
3.2
3.13
3.13
100
100
4.55
3.05
0.15
0.1
2.5
Typ
5
5
5
5
3.33
3.33
3.33
Max
5.2
5.25
5.25
3.46
3.5
3.5
Units
Ω
V
V
V
V
V
V
mA
mA
V
V
V
V
V
V
V
V
LDO Output Voltage
V
LDO
LDO Output Current
Switch Over Threshold (Rising)
Switch Over Hysteresis
SELH Input Low Voltage
SELH Input High Voltage
ENLDO Input Low Voltage
VIL
ENLDO
ENLDO Input High Voltage
VIH
ENLDO
Thermal Shutdown
Note:
5) Guaranteed by design.
6) TSS—Soft startup time
I
LDO
V
SWO
V
SWO-HYS
VIL
SELH
VIH
SELH
4.7
3.15
0.25
0.2
4.85
3.25
0.3
0.25
0.4
0.4
2
T
SD
150
°C
NB621 Rev. 0.9
12/10/2013
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2013 MPS. All Rights Reserved.
4
NB621 – 8A, 25V, 600kHz SYNCHRONOUS STEP-DOWN CONVERTER WITH INTEGRATED LDO
TYPICAL PERFORMANCE CHARACTERISTICS
NB621 Rev. 0.9
12/10/2013
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2013 MPS. All Rights Reserved.
5
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