UG-555 EVAL-ADM1073MEBZ User Guide
Rev. 0 | Page 4 of 8
EVALUATION BOARD DESCRIPTION
The E VA L -ADM1073MEBZ is designed to demonstrate several
features of the ADM1073. It can be used to drop onto a plug-in
module or a backplane, replacing the current hot swap device. A
simplified drawing of the evaluation board is shown in Figure 2.
ADM1073
DRAIN
GATE
SENSE
V
EE
OV
UV
SS
TIMER
R
SENSE
R
DROP
Q1
J1-1
J1-2 –48VRTN
–48VOUT
J1-3 –48VIN
SPLYGD
PWRGD
LA
TCHED
RESTART
SHDN
C
SS
C
TIMER
R
TIMER
R2
R1
R2
R1
11494-003
V
IN
Figure 2. Evaluation Board Functional Block Diagram
The ADM1073 evaluation board consists of the following:
• On-board FET to control load current
• Programmable operating voltage range (R1 to R4 resistors)
• Programmable current-limit levels (value of R
SENSE
)
• Programmable soft start ramp (Capacitor C2)
• Programmable TIMER on-time (Capacitor C1)
• LEDs on all logic I/Os
• Push-button switches for asserting logic inputs
By cutting various tracks around the current hot swap device in
a user system and soldering the ADM1073 evaluation board in
position above it, the ADM1073 and its external components
can be integrated into the system in place of the original hot
swap circuitry. This allows the user to evaluate the performance
of the ADM1073 in the system.
EVALUATION BOARD CONFIGURATION
You can set up the ADM1073 evaluation board in various
configurations, as follows:
1. Choose a shunt resistor. A default R
DROP
of 39 kΩ is mounted
on the ADM1073 evaluation board. A constant voltage of
12.3 V (above V
EE
) is generated at the V
IN
pin. This resistor
dissipates a maximum of 125 mW at 75 V and allows a
minimum power supply of 35 V to be used for operation.
2. Choose values for Resistors R1 to R4 to suit the desired
operating voltage range and hysteresis levels. The default
resistors values (R1 = 200 kΩ, R2 = 5.1 kΩ, R3 = 200 kΩ,
R4 = 5.36 kΩ) give an operating range of ~34.9 V to
~74.0 V with hysteresis levels of ~1 V on the UV and
OV pins. See the ADM1073 data sheet for other resistor
ratios and their operating ranges. Note that resistors that
are accurate to within ±1% should be used for optimum
accuracy.
3. Choose the maximum load current that is permitted before
the ADM1073 registers a current fault. This is determined
by the choice of sense resistor, R
SENSE
. The evaluation board
has a 15 mΩ sense resistor by default, which sets up a maxi-
mum inrush current level of 6.8 A and a circuit breaker
level between 5.7 A and 6.5 A (~6 A typical). R
SENSE
can be
changed to alter the load current level. See the ADM1073
data sheet for details. Note that resistors that are accurate
to within ±1% should be used for optimum accuracy.
4. Choose a value for the soft start capacitor, C
SS
. This capacitor
is connected between the SS and V
EE
pins. It adjusts the soft
start current profile when the FET is enabled. Capacitors
of various values can be soldered in this location. See the
ADM1073 data sheet for details. The default value of this
capacitor is 0.82 nF, which results in a soft start time of ~400 µs.
5. Choose values for the TIMER capacitor, C
TIMER
, and the
TIMER resistor, R
TIMER
. These components set the on-time
of the limited consecutive retry scheme. Capacitors and
resistors of various values can be soldered in this location.
See the ADM1073 data sheet for details. For the MOSFET
used on the board, the default value for the capacitor is 22 nF.
This gives a maximum timer of ~3 ms and a minimum timer
of ~1.1 ms. This timer depends on the V
DS
of the MOSFET;
however, C
SS
and R
DRAIN
also affect this parameter. For example,
• if V
DS
= 75 V, then t = 1.1 ms
• if V
DS
= 48 V, then t = 1.5 ms
• if V
DS
= 35 V, then t = 1.7 ms
• if V
DS
= 0 V, then t = 3 ms
6. The default value of the drain resistor is 2 MΩ. This ensures
that the maximum drain current of 36 µA is not exceeded
while maintaining optimum foldback.
7. The ADM1073 evaluation board has an IPP075N15N3
D2PAK FET mounted by default. If you want to change this
FET, remove the component, Q1, and mount a replacement.
The footprint can accommodate DPAK and D2PAK packages.
