LTC3109
OPERATION (Refer to the BloAk Diagram)
on the application and capacitor sizing, since the load on
Since the maximum charging current available at the
VSTORE output is limited to about 15mA, it can safely be
used to trickle charge NiCd or NiMH batteries for energy
storage when the input voltage is lost.
the V
output, when enabled, is likely to be orders of
OUT2
magnitude higher than 8μA.
VSTORE
Note that VSTORE is not intended to supply high pulse
The VSTORE output can be used to charge a large storage
load currents to V . Any pulse load on V
must be
OUT
OUT
capacitor or rechargeable battery. Once V
has reached
handled by the V
reservoir capacitor.
OUT
OUT
regulation, the VSTORE output will be allowed to charge
up to the clamped VAUX voltage (5.25V typical). The
storage element on VSTORE can then be used to power
the system in the event that the input source is lost, or
Short-CirAuit ProteAtion
All outputs of the LTC3109 are current limited to protect
against short circuits to ground.
is unable to provide the current demanded by the V
,
OUT
V
and LDO outputs.
OUT2
Output Voltage SequenAing
If VAUX drops below VSTORE, the LTC3109 will automati-
cally draw current from the storage element. Note that it
may take a long time to charge a large storage capacitor,
depending on the input energy available and the loading
Atimingdiagramshowingthetypicalchargingandvoltage
sequencing of the outputs is shown in Figure 1. Note that
the horizontal (time) axis is not to scale, and is used for
illustration purposes to show the relative order in which
the output voltages come up.
on V
and VLDO.
OUT
5.0
2.5
0
3.0
2.0
1.0
0
VSTORE
PGOOD
5.0
2.5
0
V
OUT
3.0
2.0
1.0
0
VLDO
VAUX
5.0
2.5
0
0
10
20
30
40
50
60
70
80
TIME (ms)
3109 F01
Figure ꢀ. Output Voltage SequenAing
(with VOUT Programmeꢂ for ±.±V). Time ꢁot to SAale
3109fa
11
Linear Systems [ Linear Systems ]
