10

Rev. 5/26/05,

*Patent Pending

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

© Copyright 2002 Sipex Corporation

APPLICATION INFORMATION: continued

TABLE 2. SP6641A Resistive Load Current in Startup - low cost inductors

GND

LX

J1

L1

22µH

U1

SP6641

SHDN

®

®

C2

22µF

+3.3V

D1

1

2

3

C1

22µF

5

4

1

2

3

+0.9V to +3.3V Input

+

+

GND

ENABLE

SP6201

®

®

RESET

1

2

3

5

4

+3.0V

C3

1µF

Figure 15. SP6641A 3.3V Evaluation Board with SP6201 LDO Regulator

SP6641A APPLICATION CIRCUIT WITH PANASONIC INDUCTOR

SP6641A APPLICATION CIRCUIT WITH TDK INDUCTOR

L1 = ELJ-PB220KF 22µH, IDCmax = 300mA, DCR = 1.0Ω

L1 = NLC453232T-220K 22µH, IDCmax = 370mA, DCR = 0.9Ω

Startup

Startup

Startup

Startup

Load

after

after

then

Load

after

after

then

Startup

Startup

Load

Startup

Startup

Load

V

Ω

VmA

mA (max)

V

Ω

VmA

mA (max)

0.86

16000

3.31

0.2

37

0.86

16000

3.30

0.2

42

0.88

1500

3.31

2

39

0.88

1500

3.30

2

43

0.90

800

3.30

4

40

0.90

900

3.30

4

44

0.95

230

3.30

14

44

0.95

260

3.30

13

48

1.00

125

3.30

26

48

1.00

126

3.30

26

52

1.10

73

3.29

45

56

1.10

66

3.29

50

60

1.20

58

3.29

57

63

1.20

49

3.29

67

69

1.30

50

3.28

66

71

1.30

43

3.29

77

77

1.40

43

3.28

76

78

1.40

39

3.29

84

84

1.50

39

3.28

84

86

1.50

36

3.29

91

91

SuperCap Application on the

SP6641 Output

When the battery input to SP6641A is removed,

the SP6641A output will end up in the charge

mode and will slowly discharge a Supercap

connected to the output. The typical Supercap

of 0.22F will go from fully charged at 3.3V to

less than 2V in 5 minutes. The following appli-

cation circuit in figure 16 is recommended to

disconnect the SP6641 output from the SuperCap

when the battery is removed. The small SOT23-

3pin MOS switches are an inexpensive addition

to the SP6641 circuit and work well to maintain

SuperCap voltage to retain Non-Volatile CMOS

Memory while a battery is changed.