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
V
BATT
J1
L1
22µH
U1
SP6641
V
OUT
SHDN
®
®
C2
22µF
V
OUT
+3.3V
D1
1
2
3
C1
22µF
5
4
1
2
3
V
BATT
+0.9V to +3.3V Input
+
+
GND
ENABLE
V
OUT
SP6201
V
IN
®
®
RESET
1
2
3
5
4
V
OUT
+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 V
OUT
I
OUT
Startup Startup V
OUT
I
OUT
Startup
Load after after then Load after after then
V
IN
R
OUT
(min) Startup Startup Load V
IN
R
OUT
(min) Startup Startup Load
V Ω VmAmA (max) V Ω VmAmA (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.
