9

Rev. 3/5/02,

*Patent Pending

SP6641A/6641B 500mA Alkaline DC/DC Boost Regulator in SOT-23

© Copyright 2002 Sipex Corporation

APPLICATION INFORMATION: continued

TABLE 1. COMPONENT SELECTION

INDUCTORS - SURFACE MOUNT

Inductor Specification

Sipex

Inductance

Manufacturer/

Series R

Isat

Size LxWxH

Inductor

Manufacturer

Part Number

(

µH)

Part Number

(

Ω)

(A)

(mm)

Type

Website

SP6641A Ipk = .33A

22

Sumida CDRH5D28-220

0.095

0.90

5.7x5.5x3

Shielded Ferrite Core

www.sumida.com

SP6641A Ipk = .33A

22

Coilcraft DO1608C-223

0.370

0.70

6.6x4.5x2.9

Unshielded Ferrite Core

www.coilcraft.com

SP6641A Ipk = .33A

22

TDK NLC453232T-220

0.900

0.37

4.4x3.2x3.2

Unshielded Ferrite Core

www.tdk.com

SP6641A Ipk = .33A

22

Murata LQH43C220K04

0.600

0.42

4.5x3.2x2.6

Unshielded Ferrite Core

www.murata.com

SP6641B Ipk = 1A

10

Sumida CDRH5D28-100

0.065

1.30

5.7x5.5x3

Shielded Ferrite Core

www.sumida.com

SP6641B Ipk = 1A

10

Coilcraft DO1608C-103

0.160

1.10

6.6x4.5x2.9

Unshielded Ferrite Core

www.coilcraft.com

SP6641B Ipk = 1A

10

Murata LQH55DN100M01

0.077

1.70

5x5x4.7

Unshielded Ferrite Core

www.murata.com

SP6641B Ipk = 1A

22

Sumida CDRH6D28-220

0.128

1.20

6.7x6.5x3

Shielded Ferrite Core

www.sumida.com

SP6641B Ipk = 1A

22

Murata LQH55DN220M01

0.160

1.20

5x5x4.7

Unshielded Ferrite Core

www.murata.com

CAPACITORS - SURFACE MOUNT & THRU-HOLE

Capacitor Specification

ESR

Ripple

Size

Sipex

Capacitance

Manufacturer/

(max)

Current

LxWxH

Voltage

Capacitor

Manufacturer

Part Number

(

µF)

Part Number

(

Ω)@ 45°C (A)

(mm)

(V)

Type

Website

SP6641A Ipk = .33A

22

TDK C3225X5R0J226M 0.010

4.00

1210

6.3

SMT X5R Cer.

www.tdk.com

SP6641B Ipk = 1A

100

SANYO 10TPA100M

0.080

1.20

7343

6.3

SMT POSCAP Tant. www.sanyovideo.com

SP6641B Ipk = 1A

100

SANYO 16SA100M

0.030

2.70

8Dx10L

16.0

Thru-hole OS-CON

www.sanyovideo.com

SCHOTTKY DIODE - SURFACE MOUNT

Diode Specification

Sipex

Manufacturer/

VF @ IF

IF(AV)

Size LxWxH

Reverse V

Package

Manufacturer

Part Number

Part Number

(V)

(A)

(mm)

(V)

Type

Website

SP6641A Ipk = .33A

STMicro STPS0520Z

0.39

0.50

3.9x1.7x1.3

20

SOD-123

www.st.com

SP6641B Ipk = 1A

Zetex ZCHS2000

0.42

2.00

3x3x1.4

40

SOT23-6

www.zetex.com

Note: Components highlighted in bold are those used on the SP6641A or SP6641B Evaluation Board.

Maximum Startup Current

It should be noted that for low input voltages the

SP6641 startup circuit can not support large

load currents at startup. In startup the SP6641

needs to boost the output from zero volts using

a charge pump which has a limited current

capacity. Once the output is greater than 1.7 to

1.9V the operate circuit takes over and the

SP6641 can supply much more current. Curves

of maximum resistive load current in startup for

the SP6641A and SP6641B are shown in Fig-

ures 13 & 14 and can be compared with Figure

2, maximum load current in operation. Also,

Table 2 provides SP6641A 3.3V resistive load

current in startup for some low cost 1812 size

chip inductors.

From the curves in Figures 13 and 14, you can

see that for low input voltages, the 22

µH induc-

tor has more current capacity at startup than the

10

µH inductor, due to more energy per charge

applications, 22

µH is recommended for more

startup current than 10

µH.

For 1-cell battery applications, it is recommended

to apply any large load current after the SP6641

has started up, typically in a few millisecs. This

is typically not a problem in many applications

where the load is a processor whose load current

is low until the processor voltage comes up.