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PDF SP6656ER Data sheet ( Hoja de datos )
| Número de pieza | SP6656ER | |
| Descripción | High Efficiency 400mA Synchronous Buck Regulator with Bit Programmable Output | |
| Fabricantes | Sipex | |
| Logotipo |  |
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® SP6656
High Efficiency 400mA Synchronous Buck Regulator with
Bit Programmable Output
FEATURES
■ 98% Efficiency Possible
■ Small 3X3 10-Pin DFN Package
■ Ultra-low 20µA Quiescent Current
■ 625mA Inductor Peak Current Limit
■ Guaranteed Minimum 400mA Output
Current
■ 2.7V to 5.5V Input Voltage Range
■ Output Adjustable Down to 1.0V
■ 100% Duty Ratio Low Dropout
Operation
■ 80µA Light Load Quiescent Current in
Dropout
■ Output Voltage Logic Selection
■ Ideal for portable designs powered with
Li Ion battery
PVIN 1
VIN 2
OVSO 3
OVSI 4
EN 5
10 LX
SP6656 9 PGND
10 Pin DFN
8 GND
7 VOUT
6 FB
Now Available in Lead Free Packaging
APPLICATIONS
■ Cell Phones
■ PDA's
■ DSC's
■ MP3 Players
■ USB Devices
■ Point of Use Power
DESCRIPTION
The SP6656 is a 400mA synchronous buck regulator that is ideal for portable applications that
use a Li-Ion or 3 cell alkaline/NiCD/NiMH input. The SP6656’s proprietary control loop, 20µA light
load quiescent current, and 0.3Ω power switches provide excellent efficiency across a wide range
of output currents. As the input battery supply decreases towards the output voltage the SP6656
seamlessly transitions into 100% duty ratio operation further extending useful battery life. The
SP6656 is protected against overload and short circuit conditions with a precise inductor peak
current limit. Other features include externally programmable output voltage down to 1.0V, logic
controlled output voltage selection, logic level shutdown control, and 140°C over temperature
shutdown.
TYPICAL APPLICATION SCHEMATIC
2.7V to 5.5V Input
VI
CIN
10Ω
RVIN
10µF
CVIN
1µF
SP6656
PVIN
LX
VIN PGND
OVSO
GND
OVSI
VOUT
EN FB
L1
10µH
COUT
10µF
RS
VOUT
400mA
VO
CF
RF 22pF
RI
Date: 7/9/04
SP6656 High Efficiency 400mA Synchronous Buck Regulator with Bit Programmable Output
1
© Copyright 2004 Sipex Corporation
1 page  
TYPICAL PERFORMANCE CHARACTERISTICS
Refer to the typical application schematic, TAMB= +27°C
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
3.6 3.9 4.2 4.5 4.8 5.1 5.4
Vin (V)
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
3.0 3.3 3.6 3.9 4.2 4.5 4.8 5.1 5.4
Vin (V)
KON vs VIN, VOUT=3.3V
KON vs VIN, VOUT=1.5V
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
3.6 3.9 4.2 4.5 4.8 5.1 5.4
Vin (V)
KOFF vs VIN, VOUT=3.3V
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
3.0 3.3 3.6 3.9 4.2 4.5 4.8 5.1 5.4
Vin (V)
KOFF vs VIN, VOUT=1.5V
700.0
600.0
500.0
400.0
300.0
200.0
100.0
0.0
3.5
Vout = 3.3V
Measured
Vout = 3.3V
Calculated
4.0 4.5
Vin (V)
5.0
Ripple Frequency vs. VIN, IOUT=0.4A, VOUT=3.3V
700.0
600.0
500.0
400.0
300.0
200.0
100.0
0.0
3.4
Vout = 1.5V
Measured
Vout = 1.5V
Calculated
3.8 4.2 4.6
Vin (V)
5.0
Ripple Frequency vs. VIN, IOUT=0.4A, VOUT=1.5V
Date: 7/9/04
SP6656 High Efficiency 400mA Synchronous Buck Regulator with Bit Programmable Output
5
© Copyright 2004 Sipex Corporation
5 Page 
THEORY OF OPERATION
mode and improves light load efficiency when
the load current is less than half the inductor
ripple current defined by KON/L.
Thermal Shutdown
The converter will open both power switches if
the die junction temperature rises above 140°C.
The die must cool down below 126°C before the
regulator is re-enabled. This feature protects the
SP6656 and surrounding circuitry from exces-
sive power dissipation due to fault conditions.
Shutdown/Enable Control
The EN pins of the device are logic level control
pins that shut down the converter when a logic
is low, or enables the converter when a logic is
high. When the converter is shut down, the
power switches are opened and all circuit bias-
ing is extinguished leaving only junction leak-
age currents on supply pins 1 and 2. After pins
4 or 5 are brought high to enable the converter,
there is a turn on delay to allow the regulator
circuitry to re-establish itself. Power conversion
begins with the assertion of the internal refer-
ence ready signal which occurs approximately
150µs after the enable signal is received.
Output Voltage Selection
The OVSI (Output Voltage Selection Input) pin
is internally driving a NMOS Gate which Drain
(OVSO pin) is used to short circuit RS and then
achieve a a higher output voltage ( see table 1 for
calculation, page 3)
External Feedback Pin
The FB pin 6 is compared to an internal refer-
ence voltage of 0.8V to regulate the SP6656
output. The output voltage can be externally
programmed within the range +1.0V to +5.0V
by tying a resistor from FB to ground and FB to
VOUT (pin7). See the applications section for
resistor selection information.
APPLICATION INFORMATION
Inductor Selection
The SP6656 uses a specially adapted minimum
on-time control of regulation utilizing a preci-
sion comparator and bandgap reference. This
adaptive minimum on-time control has the ad-
vantage of setting a constant current ripple for a
given inductor size. From the operations section
it has been shown:
Inductor Current Ripple, ILR ≈ KON
L
For the typical SP6656 application circuit with
inductor size of 10µH, and KON of 2V*µsec, the
SP6656 current ripple would be about 200mA, and
would be fairly constant for different input and
output voltages, simplifying the selection of com-
ponents for the SP6656 power circuit. Other
inductor values could be selected, as shown in
Table 2 Components Selection. Using a larger
value than 10µH in an attempt to reduce output
voltage ripple would reduce inductor current ripple
and may not produce as stable an output ripple.
For larger inductors with the SP6656, which has
a peak inductor current of 0.625A, most 15µH
or 22µH inductors would have to be larger
physical sizes, limiting their use in small por-
table applications. Smaller values like 10µH
would more easily meet the 0.625A limit and
come in small case sizes, and the increased
Date: 7/9/04
SP6656 High Efficiency 400mA Synchronous Buck Regulator with Bit Programmable Output
11
© Copyright 2004 Sipex Corporation
11 Page | ||
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