11

Date: 3/6/06

SP6656, 400mA Synchronous Buck Regulator with Dynamically Adjustable Voltage Output

© Copyright 2006 Sipex Corporation

Series R

Isat

Manufacturer

ohms

(A)

L x W

(mm)

Ht.

(mm)

Website

4.7

Murata LQH32CN4R7M53L

0.150

0.65

3.2x2.5

1.55

www.murata.com

4.7

Murata LQH31CN4R7M03L

0.65

0.34

3.2x1.6

1.8

www.murata.com

4.7

Murata LQH2MCN4R7M02L

0.80

0.30

2.0x1.6

0.9

www.murata.com

10

Murata LQH32CN100K53L

0.300

0.45

3.2x2.5

1.55

www.murata.com

10

TDK RLF5018T-100MR94

0.056

0.94

5.6x5.2

2.0

www.tdk.com

10

Coilcraft LPO6013-103K

0.300

0.70

6.0x5.4

1.3

www.coilcraft.com

22

Murata LQH32CN220K21

0.710

0.25

3.2x2.5

2.0

www.murata.com

22

TDK RLF5018T-220MR63

0.130

0.63

5.6x5.2

2.0

www.tdk.com

22

Coilcraft LPO6013-223K

0.520

0.45

6.0x5.4

1.3

www.coilcraft.com

ESR

Ripple

Current

Voltage

Capacitor

Manufacturer

ohms

(max)

(A) @

45C

L x W

(mm)

Ht.

(mm)

(V)

Type

Website

10

TDK C2012X5R0J106M

0.003

1.00

2.0x1.2

1.25

6.3

X5R Ceramic

www.tdk.com

10

Murata GRM21BR60J106KE01

0.003

1.00

2.0x1.2

1.25

6.3

X5R Ceramic

www.murata.com

4.7

TDK C2012X5R0J475M

0.005

1.00

2.0x1.2

1.25

6.3

X5R Ceramic

www.tdk.com

4.7

Murata GRM21BR60J475KE01

0.005

1.00

2.0x1.2

1.25

6.3

X5R Ceramic

www.murata.com

Note: Components highlighted in bold are those used on the SP6656 Evaluation Board.

Shielded Ferrite Core

Unshielded Ferrite Core

Unshielded Ferrite Core

Unshielded Ferrite Core

Shielded Ferrite Core

Unshielded Ferrite Core

Unshielded Ferrite Core

Inductor Specification

Unshielded Ferrite Core

Unshielded Ferrite Core

INDUCTORS - SURFACE MOUNT

CAPACITORS - SURFACE MOUNT

Capacitance

(uF)

Inductance

(uH)

Size

Inductor Type

Size

Capacitor Specification

Manufacturer/Part No.

Manufacturer/Part No.

when the load current is less than half the

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 fea-

ture protects the SP6656 and surrounding

circuitry from excessive power dissipation

due to fault conditions.

Shutdown/Enable Control

The EN pin of the device is a logic level

control pin that shuts down the converter

when logic is low, or enables the converter

when logic is high. When the converter is

shut down, the power switches are opened

and all circuit biasing is extinguished leav-

ing only junction leakage currents on supply

pins 1 and 2. After pin 5 is brought high to

enable the converter, there is a turn on

delay to allow the regulator circuitry to rees-

tablish itself. Power conversion begins with

the assertion of the internal reference 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

and then achieve a higher output voltage (

see table 1 for calculation, page 3)

External Feedback Pin

The FB pin 6 is compared to an internal

reference 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

applications section for resistor selection

information.

Inductor Selection

The SP6656 uses a specially adapted mini-

mum on-time control of regulation utilizing a

precision comparator and bandgap refer-

ence. This adaptive minimum on-time con-

trol has the advantage of setting a constant

current ripple for a given inductor size.

Fromtheoperationssectionithasbeenshown:

L

THEORY OF OPERATION

APPLICATION INFORMATION

For the typical SP6656 application circuit with

the SP6656 current ripple would be about

200mA, and would be fairly constant for differ-

ent input and output voltages, simplifying the

selectionofcomponentsfortheSP6656power

circuit. Other inductor values could be se-

lected, 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

Table 2 Component Selection