1
dc2160af
DEMO MANUAL DC2160A
DESCRIPTION
LTC4419
18V Dual Input Micropower
PowerPath™ Prioritizer
Demonstration circuit 2160A uses the
LTC
®
4419
to
provide backup switchover, keeping the output load
powered during brown out or power loss conditions.
Priority is assigned by supply connection to the V1 and
V2 inputs. The power source connected to V1 has a higher
priority and is monitored by undervoltage switchover
threshold comparator CADJ (pin ADJ). If V1 exceeds
1.55V and ADJ is above 1.097V for 64ms, V1 is considered
valid, and the LTC4419 connects V1 to the load. If V1
drops below 1.52V, or ADJ drops below 1.047V, V1 is
considered invalid, and the LTC4419 powers the load
from V2. The DC2160A is populated to provide switchover
when V1 drops below 10.19V ±0.33V. The upper limit for
V1 is the maximum operating voltage, 18V; however, the
recommended V1 voltage is 12V. The resistive divider (R1-
R2) of the first auxiliary comparator CMP1 is adjusted to
trigger the comparator when VCMP1_TOP’s voltage is in
the 9.92V to 10.74V range. Practically, any voltage from
the operating range can be selected for V2, however, 5V
is recommended to have a standard voltage level.
L
, LT, LTC, LTM, Linear Technology, and the Linear logo are registered trademarks and
PowerPath is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
PERFORMANCE SUMMARY
The second auxiliary comparator CMP2 divider (R8-R7) is
adjusted to trigger the comparator when VCMP2_TOP’s
voltage is in the 3.26V to 3.53V range. Overcurrent (0.5A
to 1.6A) and thermal protection inherent to the LTC4419
allows safe prioritization. Overtemperature protection is
activated when the junction temperature exceeds 125ºC.
Another inherent feature – reverse supply protection –
protects the prioritizer and load when a negative voltage
(up to –15V) is applied to any input – V1 or V2.
The LTC4419’s “break-before-make” switching method
prevents cross conduction between input channels. The
LTC4419 does not connect any input source to the load
until the input voltage exceeds the output by 50mV. This
eliminates reverse current from the output into the selected
input supply.
Design files for this circuit board are available at
http://www.linear.com/demo/DC2160A
Specifications are at T
A
= 25°C
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V1, V2, V
OUT
V1, V2, V
OUT
Operating Supply Range
1.8
18
V
R
ON
Switch Resistance
V1 = V2 = 5V, I
OUT
= –100μA
1
2
5
Ω
t
VALID(V1)
Input Qualification Time
V1 Rising, ADJ Rising
34
64
94
ms
V
THA
ADJ Threshold
ADJ Falling
1.032
1.047
1.062
V
V
HYSTA
ADJ Comparator Hysteresis
ADJ Rising
30
50
70
mV
V
THC
CMP1, CMP2 Threshold
CMP1, CMP2 Falling
0.378
0.387
0.396
V
V
HYSTC
CMP1, CMP2 Hysteresis
CMP1, CMP2 Rising
7.5
10
12.5
mV
I
LIM
Current Limit
V1 = V2 = 8.4V
0.5
1.1
1.6
A
V
REV
Reverse Comparator Threshold
(V1, V2) – V
OUT
for Power Path Turn-On
25
50
75
mV
t
SWITCH
Switch Break-Before-Make Time
V1 = V2 = 5V, I
OUT
< –10mA
1
2.5
5
µs
V
1_SWITCHOVER
Demo Board Switchover Voltage
9.6
9.92
10.24
V
V
1_ALARM
Demo Board V1 Alarmed Voltage
9.92
10.32
10.74
V
V
2_ALARM
Demo Board V2 Alarmed Voltage
3.26
3.38
3.53
V
