SP6641BEK-L-5-0-TR Datasheet, PDF (9/14 Pages) Exar Corporation – 500mA Alkaline DC/DC Boost Regulator in SOT-23

APPLICATION INFORMATION: continued
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 22µH induc-
tor has more current capacity at startup than the
10µH inductor, due to more energy per charge
cycle in the relationship ¹/2LI². Thus for 1 cell
applications, 22µH is recommended for more
startup current than 10µH.
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.
TABLE 1. COMPONENT SELECTION
INDUCTORS - SURFACE MOUNT
Sipex
Part Number
Inductance
(µH)
Manufacturer/
Part Number
Series R
(Ω)
SP6641A Ipk = .33A 22 Sumida CDRH5D28-220 0.095
Inductor Specification
Isat Size LxWxH
(A)
(mm)
Inductor
Type
0.90 5.7x5.5x3 Shielded Ferrite Core
SP6641A Ipk = .33A 22 Coilcraft DO1608C-223 0.370 0.70 6.6x4.5x2.9 Unshielded Ferrite Core
SP6641A Ipk = .33A 22 TDK NLC453232T-220 0.900 0.37 4.4x3.2x3.2 Unshielded Ferrite Core
SP6641A Ipk = .33A 22 Murata LQH43C220K04 0.600 0.42 4.5x3.2x2.6 Unshielded Ferrite Core
SP6641B Ipk = 1A
10 Sumida CDRH5D28-100 0.065 1.30 5.7x5.5x3 Shielded Ferrite Core
SP6641B Ipk = 1A
10 Coilcraft DO1608C-103 0.160 1.10 6.6x4.5x2.9 Unshielded Ferrite Core
SP6641B Ipk = 1A
10 Murata LQH55DN100M01 0.077 1.70 5x5x4.7
Unshielded Ferrite Core
SP6641B Ipk = 1A
22 Sumida CDRH6D28-220 0.128 1.20 6.7x6.5x3
Shielded Ferrite Core
SP6641B Ipk = 1A
22 Murata LQH55DN220M01 0.160 1.20 5x5x4.7
Unshielded Ferrite Core
Manufacturer
Website
www.sumida.com
www.coilcraft.com
www.tdk.com
www.murata.com
www.sumida.com
www.coilcraft.com
www.murata.com
www.sumida.com
www.murata.com
CAPACITORS - SURFACE MOUNT & THRU-HOLE
Capacitor Specification
Sipex
Part Number
Capacitance
(µF)
Manufacturer/
Part Number
SP6641A Ipk = .33A 22 TDK C3225X5R0J226M
ESR
(max)
(Ω)
0.010
Ripple
Current
@ 45°C (A)
4.00
Size
LxWxH
(mm)
1210
Voltage
(V)
6.3
Capacitor
Type
SMT X5R Cer.
Manufacturer
Website
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
Part Number
Manufacturer/
Part Number
VF @ IF
(V)
IF(AV)
(A)
Size LxWxH
(mm)
Reverse V
(V)
Package
Type
SP6641A Ipk = .33A STMicro STPS0520Z
0.39
0.50
3.9x1.7x1.3
20
SOD-123
SP6641B Ipk = 1A
Zetex ZCHS2000
0.42
2.00
3x3x1.4
40
SOT23-6
Note: Components highlighted in bold are those used on the SP6641A or SP6641B Evaluation Board.
Manufacturer
Website
www.st.com
www.zetex.com
Rev. 5/26/05, *Patent Pending
SP6641A/6641B 500mA Alkaline DC/DC Boost Regulator in SOT-23
9
© Copyright 2002 Sipex Corporation