Datasheet

LTC4417
19
4417f
priority back up input supplies. An internal diode-OR
structure selects the highest voltage input supply as the
source for VB
LDO
. If two supplies are similar in voltage and
higher than the remaining input supply, the current will be
equally divided between the similar voltage supplies. If all
input supplies are equal in voltage, the current is divided
evenly between them.
To limit current consumption from lower priority backup
supplies, the LTC4417 prioritizes the internal V
LDO
’s source
supply. The highest priority source is V
OUT
, which powers
the V
LDO
when V
OUT
is above 2.4V. If V
OUT
is lower than
2.4V, V
LDO
switches to the highest valid priority input
supply, V1, V2 and V3. If no input supply is valid, V
LDO
is connected to VB
LDO
, where the diode-OR selects high-
est input voltage input supply as the source. See Typical
Performance Characteristics for more detail.
DUAL SUPPLY OPERATION
For instances where only two supplies are prioritized and
no features of the third channel are used, ground the
V3, OV3, UV3, VS3 and G3 pins of the unused channel.
Alternatively, the lowest priority OV and UV comparators
can be utilized for voltage monitoring when V3 and
VS3
are connected to the output and G3 is left open. Figure11
shows an example of the spare OV and UV comparators
used to monitor the 5V output of the LTC3060. VALID3
acts as an open drain OV/UV window comparator output.
Figure 11. Dual Channel with Output Voltage Monitoring
VS1
V1 V
OUT
5V OUTPUT
VALID1
VALID2
VALID3
12V WALL
ADAPTER
C
IN
2200µF
14.4V NiCd
BATTERY
UV1
OV1
R3
806k
R2
39.2k
R1
60.4k
R6
845k
R5
26.1k
R4
51.1k
R9
340k
R8
21.5k
R7
78.7k
R10
1M
R11
1M
R12
1M
V1 INVALID
V2 INVALID
5V OUTPUT INVALID
V2
UV2
OV2
V3 EN
SHDN
HYS
CAS
UV3
OV3
4417 F11
G1 VS2 VS3G2
GND
LTC4417
G3
C
V1
0.1µF
C
VS2
1µF
C
VS1
0.1µF
C
V2
0.1µF
C
V3
0.1µF
+
C
L
100µF
V
OUT
+
+
LTC3060
LINEAR
REGULATOR
IRF7324
M3 M4
IRF7324
M1 M2
C
S
6.8nF
R
S
2.21k
D
S
BAT54