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PDF SP7651 Data sheet ( Hoja de datos )
| Número de pieza | SP7651 | |
| Descripción | Wide Input Voltage Range 3A / 900kHz / Buck Regulator | |
| Fabricantes | Sipex | |
| Logotipo |  |
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®
Advanced
SP7651
Wide Input Voltage Range 3A, 900kHz, Buck Regulator
FEATURES
■ 2.5V to 20V Step Down Achieved Using Dual Input
■ Output Voltage down to 0.8V
■ 3A Output Capability (Up to 5A with Air Flow)
■ Built in Low RDSON Power FETs (40 mΩ typ)
■ Highly Integrated Design, Minimal Components
■ 900 kHz Fixed Frequency Operation
■ UVLO Detects Both VCC and VIN
■ Over Temperature Protection
■ Short Circuit Protection with Auto-Restart
■ Wide BW Amp Allows Type II or III Compensation
■ Programmable Soft Start
■ Fast Transient Response
■ High Efficiency: Greater than 92% Possible
■ Asynchronous Start-Up into a Pre-Charged Output
■ Small 7mm x 4mm DFN Package
SP7651
DFN PACKAGE
7mm x 4mm
PGND 1
PGND 2
PGND 3
GND 4
VFB 5
COMP 6
UVIN 7
GND 8
SS 9
VIN 10
VIN 11
VIN 12
VIN 13
TOP VIEW
Heatsink Pad 1
Connect to Lx
Heatsink pad 2
Connect to GND
Heatsink pad 3
Connect to VIN
26 LX
25 LX
24 LX
23 LX
2 2 VCC
21 GND
20 GND
19 GND
18 BST
17 NC
16 LX
15 LX
14 LX
Now Available in Lead Free Packaging
DESCRIPTION
The SP7651 is a high voltage synchronous step-down switching regulator optimized for high efficiency. The part is
designed to be especially attractive for dual supply, 12V step down with 5V used to power the controller. This lower VCC
voltage minimizes power dissipation in the part. The SP7651 is designed to provide a fully integrated buck regulator
solution using a fixed 900kHz frequency, PWM voltage mode architecture. Protection features include UVLO, thermal
shutdown and output short circuit protection. The SP7651 is available in the space saving 7mm X 4mm DFN package.
TYPICAL APPLICATION CIRCUIT
CZ2 RZ2
1,000pF 15k,1%
CP1
CF1
100pF
22pF
ENABLE
CSS
15nF
VIN
12V
GND
C1
22uF
16V
1
PGND
2
PGND
3
PGND
4 GND
5 VFB
6 COMP
7
UVIN
8
GND
9
SS
10 VIN
11 VIN
12 VIN
13
VIN
U1
SP7651
LX
LX
LX
LX
VCC
GND
GND
GND
BST
NC
LX
LX
LX
26
25
24
23
22
21
20
19
18
17
16
15
14
fs=900Khz
L1
4.7uH, Irate=3.87A
CVCC
2.2uF
DBST
C3
22uF
6.3V
SD101AWS
CBST
6800pF
+5V VCC
Notes:
1. U1 Bottom-Side Layout should
has three contacts isolated from
one another Vin SWNODE and GND
2. RSET=54.48/(Vout-0.8V) (KOhm)
RZ3
7.15k,1%
CZ3
150pF
VOUT
3.3V
0-3A
R1
68.1k,1%
RSET
21.5k,1%
(note 2)
Date: 08/25/04
SP7651 Wide Input Voltage Range 3A, 900kHz, Buck Regulator
1
© Copyright 2004 Sipex Corporation
1 page  
clude thermal shutdown and short-circuit detec-
tion. In the event that either a thermal, short-
circuit, or UVLO fault is detected, the SP7651 is
forced into an idle state where the output drivers
are held off for a finite period before a re-start is
attempted.
Soft Start
“Soft Start” is achieved when a power converter
ramps up the output voltage while controlling
the magnitude of the input supply source cur-
rent. In a modern step down converter, ramping
up the positive terminal of the error amplifier
controls soft start. As a result, excess source
current can be defined as the current required to
charge the output capacitor.
IVIN = COUT * (DVOUT / DTSOFT-START)
The SP7651 provides the user with the option to
program the soft start rate by tying a capacitor
from the SS pin to GND. The selection of this
capacitor is based on the 10uA pull up current
present at the SS pin and the 0.8V reference
voltage. Therefore, the excess source can be
redefined as:
IVIN = COUT * (DVOUT *10µA / (CSS * 0.8V)
Under Voltage Lock Out (UVLO)
The SP7651 contains two separate UVLO com-
parators to monitor the internal bias (VCC) and
conversion (VIN) voltages independently. The
VCC UVLO threshold is internally set to 4.25V,
whereas the VIN UVLO threshold is program-
mable through the UVIN pin. When the UVIN
pin is greater than 2.5V, the SP7651 is permitted
to start up pending the removal of all other
faults. Both the VCC and VIN UVLO compara-
tors have been designed with hysteresis to pre-
vent noise from resetting a fault.
THEORY OF OPERATION
Thermal and Short-Circuit
Protection
Because the SP7651 is designed to drive large
output current, there is a chance that the power
converter will become too hot. Therefore, an
internal thermal shutdown (145°C) has been
included to prevent the IC from malfunctioning
at extreme temperatures.
A short-circuit detection comparator has also
been included in the SP7651 to protect against
an accidental short at the output of the power
converter. This comparator constantly monitors
the positive and negative terminals of the error
amplifier, and if the VFB pin falls more than
250mV (typical) below the positive reference, a
short-circuit fault is set. Because the SS pin
overrides the internal 0.8V reference during soft
start, the SP7651 is capable of detecting short-
circuit faults throughout the duration of soft
start as well as in regular operation.
Handling of Faults:
Upon the detection of power (UVLO), thermal,
or short-circuit faults, the SP7651 is forced into
an idle state where the SS and COMP pins are
pulled low and the NFETS are held off. In the
event of UVLO fault, the SP7651 remains in this
idle state until the UVLO fault is removed.
Upon the detection of a thermal or short-circuit
fault, an internal 200ms timer is activated. In the
event of a short-circuit fault, a re-start is at-
tempted immediately after the 200ms timeout
expires. Whereas, when a thermal fault is de-
tected the 200ms delay continuously recycles
and a re-start cannot be attempted until the
thermal fault is removed and the timer expires.
Error Amplifier and Voltage Loop
Since the heart of the SP7651 voltage error loop
is a high performance, wide bandwidth
transconductance amplifier great care should be
taken to select the optimal compensation net-
work. Because of the amplifier’s current lim-
ited (+/-150µA) transconductance, there are
many ways to compensate the voltage loop or to
Date: 08/25/04
SP7651 Wide Input Voltage Range 3A, 900kHz, Buck Regulator
5
© Copyright 2004 Sipex Corporation
5 Page 
D
E (7 x 4 mm)
Top View
PACKAGE: 26 PIN DFN
A
A1
L
Side View
e
b
D2 D3 D2
Bottom View
A3
E2
26 Pin DFN
SYMBOL
A
A1
A3
b
D
D2
D3
e
E
E2
L
DIMENSIONS in
(mm)
MIN NOM MAX
0.800 0.850 0.900
0.000 - 0.050
0.178 0.203 0.228
0.17 0.22 0.27
6.95 7.00 7.05
2.00 2.05 2.10
1.78 1.83 1.88
0.45 0.50 0.55
3.95 4.00 4.05
2.730 2.780 2.830
0.350 0.400 0.450
Date: 08/25/04
26 Pin DFN
SP7651 Wide Input Voltage Range 3A, 900kHz, Buck Regulator
11
© Copyright 2004 Sipex Corporation
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet SP7651.PDF ] | |
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