ADUM5401_VB AD [Analog Devices], ADUM5401_VB Datasheet - Page 23

• Manufacturer Part Number: ADUM5401_VB
• Description: Quad-Channel, 2.5 kV Isolators with Integrated DC-to-DC Converter
• Manufacturer: AD [Analog Devices]

Data Sheet
The maximum external load can be calculated by subtracting
the dynamic output load from the maximum allowable load.
where:
I
side load.
I
available at V
I
or output channel, as shown in Figure 23 and Figure 24.
The preceding analysis assumes a 15 pF capacitive load on each
data output. If the capacitive load is larger than 15 pF, the additional
current must be included in the analysis of I
POWER CONSIDERATIONS
The
input, data input channels on the primary side, and data channels
on the secondary side are all protected from premature operation
by under voltage lockout (UVLO) circuitry. Below the minimum
operating voltage, the power converter holds its oscillator inactive
and all input channel drivers and refresh circuits are idle. Outputs
remain in a high impedance state to prevent transmission of
undefined states during power-up and power-down operations.
During application of power to V
is held idle until the UVLO preset voltage is reached. At that
time, the data channels initialize to their default low output
state until they receive data pulses from the secondary side.
When the primary side is above the UVLO threshold, the data
input channels sample their inputs and begin sending encoded
pulses to the inactive secondary output channels. The outputs
on the primary side remain in their default low state because no
data comes from the secondary side inputs until secondary side
power is established. The primary side oscillator also begins to
operate, transferring power to the secondary power circuits.
The secondary V
the regulation control signal from the secondary side is not being
generated. The primary side power oscillator is allowed to free
run under these conditions, supplying the maximum amount of
power to the secondary side.
As the secondary side voltage rises to its regulation setpoint,
a large inrush current transient is present at V
regulation point is reached, the regulation control circuit produces
the regulation control signal that modulates the oscillator on
the primary side. The V
proportional to the load current. The inrush current is less than
the short-circuit current shown in Figure 14. The duration of
the inrush current depends on the V
on the current and voltage available at the V
ISO (LOAD)
ISO (MAX)
ISO (D)n
ADuM5401/ADuM5402/ADuM5403/ADuM5404
I
ISO (LOAD)
is the dynamic load current drawn from V
is the maximum external secondary side load current
is the current available to supply an external secondary
ISO
= I
.
ISO (MAX)
ISO
voltage is below its UVLO limit at this point;
− Σ I
DD1
current is then reduced and is
ISO (D)n
DD1
; n = 1 to 4
, the primary side circuitry
ISO
loading conditions and
DD1
DD1
DD1
and I
pin.
. When the
ISO
by an input
ISO (LOAD)
power
.
Rev. B | Page 23 of 28
(2)
ADuM5401/ADuM5402/ADuM5403/ADuM5404
As the secondary side converter begins to accept power from
the primary, the V
side UVLO is reached, the secondary side outputs are initialized
to their default low state until data is received from the corre-
sponding primary side input. It can take up to 1 μs after the
secondary side is initialized for the state of the output to
correlate to the primary side input.
Secondary side inputs sample their state and transmit it to the
primary side. Outputs are valid about 1 μs after the secondary
side becomes active.
Because the rate of charge of the secondary side power supply is
dependent on loading conditions, the input voltage, and the output
voltage level selected, take care that the design allows the converter
sufficient time to stabilize before valid data is required.
When power is removed from V
and coupler shut down when the UVLO level is reached. The
secondary side stops receiving power and starts to discharge.
The outputs on the secondary side hold the last state that they
received from the primary side. Either the UVLO level is
reached and the outputs are placed in their high impedance
state, or the outputs detect a lack of activity from the primary
side inputs and the outputs are set to their default low value
before the secondary power reaches UVLO.
INCREASING AVAILABLE POWER
The
designed with the capability of running in combination with
other compatible isoPower devices. The RC
ADuM5401/ADuM5402/ADuM5403/ADuM5404
PWM signal to another device acting as a master to regulate its
self and slave devices. Power outputs are combined in parallel
while sharing output power equally.
The
be a master/standalone, and the
standalone device. The
or slave. This means that the ADuM5000, ADuM520x, and
ADuM540x can only be used in the master/slave combinations
listed in Table 26.
Table 26. Allowed Combinations of isoPower Parts
Master
ADuM5000
ADuM520x
ADuM540x
The allowed combinations of master and slave configured parts
listed in Table 26 is sufficient to make any combination of power
and channel count.
ADuM5401/ADuM5402/ADuM5403/ADuM5404
ADuM5401/ADuM5402/ADuM5403/ADuM5404
ADuM5000
Yes
No
Yes
ISO
voltage starts to rise. When the secondary
ADuM5000
ADuM5200
DD1
ADuM520x
Yes
No
Yes
can operate as either a master
, the primary side converter
Slave
can only be a slave/
OUT
pin allows the
ADuM540x
No
No
No
to provide its
are
can only