LTC4417_15 Datasheet, PDF (19/32 Pages) Linear Technology – Prioritized PowerPat Controller

LTC4417
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.
C_V3
0.1µF
12V WALL
ADAPTER
+ _CIN
2200µF
14.4V NiCd
BATTERY
+
IRF7324
M1
M2
M3
C_VS1
0.1µF
C_VS2
1µF
IRF7324
M4
D_S
BAT54
R_S
2.21k
C_S
6.8nF
+
C_L
V_OUT
100µF
LTC3060
LINEAR
REGULATOR
C_V2
0.1µF
R9
340k
R8
21.5k
R7
78.7k
C_V1
0.1µF
R6
845k
R5
26.1k
R4
51.1k
VS1 G1
V1
R3
806k
UV1
R2
39.2k
OV1
R1
60.4k
V2
UV2
OV2
V3
UV3
OV3
VS2
G2 VS3 G3
V_OUT
5V OUTPUT
R10 R11 R12
1M 1M 1M
VALID1
VALID2
VALID3
V1 INVALID
V2 INVALID
5V OUTPUT INVALID
LTC4417
GND
EN
SHDN
HYS
CAS
4417 F11
Figure 11. Dual Channel with Output Voltage Monitoring
4417f
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