LTC4416/LTC4416-1
7
4416fa
The band-gap reference provides internal bias currents
used by the channel 1 and channel 2 controllers. It also
provides a precision voltage reference, V
REF
, used by com-
parators C1 and C2. The band-gap reference is powered
as long as a minimum operational voltage is present on
either V1, V2, or V
S
.
The C1 and C2 comparators provide a fixed comparison
between the E1 and E2 inputs, respectively, and the in-
ternal V
REF
signal. The comparator outputs are directly
represented by the H1 and H2 open-drain outputs. The
output states of H1 and H2 are not dependent upon
the relative voltage difference between V
V1
– V
VS
and
V
V2
– V
VS
, respectively. If V
E1
is less than V
REF
, the H1
open-drain output will be low impedance to GND. If V
E2
is less than V
REF
, the H2 open-drain output will be low
impedance to GND.
The A1 and A2 circuits act both as a high side
transconductance amplifiers and as comparators. Both
A1 and A2 act identically when the analog controllers
are fully enabled. The relationship of the G1 current is
represented by Figure 1.
When V
V1
– V
VS
< V
RTO
, the A1 activates the reverse turn-
off condition and the I
G1
current is I
G(OFF)
. When V
RTO
<
V
V1
– V
VS
< V
FR
, the A1 acts as a class A output and the
I
G1
current is fixed at I
G(SRC)
. As the V
V1
– V
VS
voltage
V
V1
– V
VS
4416 F01
I
G1
V
RTO
V
FR
V
FON
I
GFON(SNK)
I
G(SNK)
I
G(SRC)
I
G(OFF)
NOT DRAWN TO SCALE
Figure 1. I
G1
vs V
V1
– V
VS
approaches the forward regulation voltage, V
FR
, the I
G(SNK)
current will be proportional to V
V1
– V
VS
. When V
V1
– V
VS
> V
FON
, the A1 activates the fast-on condition, t
G(ON)
, and
the I
G1
current is set to I
GFON(SNK)
.
LTC4416 OPERATION
The interaction of the LTC4416 analog controllers distin-
guish the operation of the LTC4416 from a simple circuit
using two PowerPath controllers. Table 1 explains the
different operation modes of the analog controllers.
Table 1. LTC4416 Operational Modes
E1 E2 Operation Mode I
G(OFF)1
I
G(OFF)2
1 0 Load Sharing Enabled Enabled
1 Sense V1 is Less Than V2 Enabled
Sense 0 V1 is Greater Than V2 Enabled
0 X Channel 1 Disabled.
Do Not Use
Disabled
X 1 Channel 2 Disabled.
Do Not Use
Disabled
0 1 Both Channels Disabled Disabled Disabled
The LTC4416 has six modes of operation. Each mode of
operation is dependent upon the configuration of the E1
and E2 input pins.
Load Sharing Operation
The load sharing mode configures the LTC4416 into two
independent PowerPath controllers. This is accomplished
by fully enabling both the first analog controller and the
second analog controller. Both channels will implement
the gate drive outlined in Figure 1.
V1 is Less Than V2 Operation
Channel 1 is fully enabled. If V
V1
– V
VS
< V
RTO
, channel 1
will implement all of the I
G1
currents listed in Figure 1.
When V
E2
is above the V
REF
threshold, channel 2 is in a
“soft-off mode”. This means that G2 will only provide an
I
G(SRC)
current instead of either an I
G(SRC)
or an I
G(OFF)
current.
When V
E2
is below the V
REF
threshold, channel 2 is fully
enabled, and G2 will become active implementing the I
G
output current listed in Figure 1.
