ISL6144_14 Datasheet, PDF (16/30 Pages) Intersil Corporation – High Voltage ORing MOSFET Controller

ISL6144
Input Voltage Range (+9V to +75V)
The ISL6144 can operate in equipment with voltages in the
+9V to +75V range. The ISL6144 can also be used in
systems with negative voltages -9V to -75V, but it has to be
placed on the return (high) side. For example, in ATCA
systems, an ORing of both the low (-48V) and high (-48V
Return) sides is required. In this case the ISL6144 can be
used on the high side.
The ISL6144 draws bias from both the input and output
sides. External bias voltage rail is not needed and cannot be
used. As soon as the Input voltage reaches the minimum
operational voltage, the internal charge pump turns on and
provides gate voltage to turn-on the ORing FET.
Multiple Feed ORing (ISL6144EVAL1Z)
In today’s high availability systems, two or more power
supplies can be paralleled to provide redundancy and fault
tolerance. These paralleled power supplies operate in an
active ORing mode where all of these supplies share the
load current, depending on the redundancy scheme
implemented in the particular system. The power system
must be able to continue its normal operation, even in the
event of one or more failures of these power supplies. Faults
occurring on the power supply side need to be isolated from
the common bus point connected to the system critical
loads. This fault isolation device is known as the ORing
device. The function of the ORing device is to pass the
forward supply current flowing from the power supply side
and block the reverse fault current. A fault current might flow
if a short occurs on the input side (typically this could be a
power supply output capacitor short). In this case, the input
voltage drops and current may flow in the reverse direction
from the load to the input, causing the common bus to drop
and the system to fail. Although ORing diodes are simple to
implement in such systems, they suffer from many
drawbacks, as outlined earlier.
The ISL6144 (with an external N-Channel MOSFET)
provides an integrated solution to perform the ORing
function in high availability systems, while increasing power
system efficiency at the same time.
Operating Instructions and Functional
Tests
Test setup for ISL6144EVAL1Z is shown in Figures 16 and
17 with two options for the input power sources.
Option 1: Using two identical bench power supplies (BPS)
connected directly to the ISL6144EVAL1Z Control Board
(refer to Figure 16). Just make sure to program the voltages
on PS1_V1 and PS2_V2 to identical values so that they
share the load current. A MOSFET (Q_short) is connected at
the Input of one or both feeds as close as possible to the
input connectors of the ISL6144EVAL1Z board. Slow turn-off
of the input BPS can be performed by the on/off button
(depending on the output capacitance value of the power
supply/module, a local loading resistor might be needed to
help discharge the BPS output capacitor). An output
capacitor C_OUT (equivalent to the capacitor that will be used
in the final power system solution) is connected to the
Common Bus point (V_OUT). Different types of loads can be
used (power resistors, electronic load or simply another
DC/DC converter).
Option 2: Using a custom designed DC/DC converter Power
Board which consists of two DC/DC modules connected in
current sharing configuration, each DC/DC module output
can be turned off slowly using the ON/OFF pin or can be
shorted using on-board Power MOSFET (Refer to
Figure 17). In this case also, similar considerations for C_OUT
and type of load apply as in option 1.
AUX PS* +
5V ^-
USED ONLY FOR POWERING THE LEDS
PS1_V1 = V_IN1
+
PS1
Q_SHORT
J4
J1
V_IN1 5V_AUX
+48V ^PS1_V1RTN
J6
-
PS2_V2 = V_IN2
+
PS2
GND
J7
V_IN2
J2
V_OUT
J3
GND
C_OUT
L
O
A
D
+48V
PS2_V2RTN
J8
BENCH POWER
SUPPLIES
GND
ISL6144EVAL1Z
CONTROL
BOARD
*Auxiliary power supply is used to power the LED circuit. If V_OUT is
less than 16V, J1 can be connected directly to V_OUT (J5). If V_OUT is
higher than 16V, we still can use V_OUT to replace AUX PS, but a
zener diode has to be connected from FAULT to GND to clamp the
voltage across the pin to 16V or lower.
FIGURE 16. TEST SETUP USING BENCH PS
.
AUX
PS
+
-
USED ONLY FOR POWERING THE LEDs
PS1_V1
+
PS1
+48V PS1_V1RTN
J4
J1
V_OUT1
DC/DC 1
J2
J6
-
PRI_GND _GND
PS2_V2
+
PS2
CS
J7
J3
V_OUT2
+48V
PS2_V2RTN
DC/DC 2
J8
-
J9
PRI_GND GND
BENCH POWER
SUPPLIES
POWER MODULES
BOARD*
J4
J1
V_IN1 5V_AUX
J6
GND
J2
V_OUT
J7
V_IN2
J3
GND
C_OUT
L
O
A
D
J8
GND
ISL6144EVAL1Z
CONTROL
BOARD
*Power Modules Board can be replaced by bench power supplies or
any discrete DC/DC modules. Just make sure to adjust both V_OUT1
and V_OUT2 close to each other to allow current sharing between the
two modules (Refer to option 1 and Figure17).
FIGURE 17. TEST SETUP USING DC/DC MODULES
16
FN9131.7
October 6, 2011