LTC1559CS-5 View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTC1559CS-5' PDF : 20 Pages View PDF
LTC1559-3.3/LTC1559-5
APPLICATIONS INFORMATION
The LTC1559 works with standard or memory backup
specific NiCd cells. Memory backup cells can operate at
higher temperatures and have lower self-discharge rates.
The LTC1559’s trickle charger is designed to accommo-
date both memory backup cells (with low self-discharge)
and standard cells (with higher self-discharge). Some
recommended manufacturers and part numbers are listed
in Table 4.
The internal resistance of the backup cell increases power
dissipation as the boost converter draws current from it
during switching, degrading efficiency. Due to the fixed
inductor peak current architecture, the LTC1559’s boost
converter output power drops significantly when the NiCd
cell’s internal resistance increases at the end of its charge.
The inductor charging time increases due to a larger R/L
time constant, decreasing the switching frequency. It is
advisable, especially for batteries with high internal resis-
tance, to include a 1µF or larger bypass capacitor across
the battery to ensure that the boost converter can deliver
the maximum output power regardless of the NiCd inter-
nal resistance.
Table 4. Button/Cylindrical NiCd 1.2V Cells
MANUFACTURER
(TYPE)
PART
NUMBER
CAPACITY
(mAhr)
SAFT
GB60
60
(Memory Backup)
GB170
170
GB280
280
SAFT
(Standard)
VB10E
100
VB22E
220
VB30E
300
VB60E
600
Sanyo
(Standard)
N-50AAA
55
N-110AA
120
N-120TA
130
N-150N
170
N-200AAA
220
N-270AA
305
N-500A
500
Panasonic (Standard) P-11AA
110
RSERIES
(Ω)
1.1
0.4
0.4
0.038
0.022
0.017
0.014
0.055
0.03
0.034
0.027
0.021
0.015
0.09
0.08
15
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