EVAL-ADM1073MEB View Datasheet(PDF) - Analog Devices
Part Name
Description
MFG CO.
'EVAL-ADM1073MEB' PDF : 24 Pages View PDF
ADM1073
FUNCTIONAL DESCRIPTION
HOT CIRCUIT INSERTION
INITIAL STARTUP
Inserting circuit boards into a live −48 V backplane can cause
large transient currents to be drawn as the board capacitance
charges up. These transient currents can cause glitches on the
system power supply and can permanently damage the board
connectors and components.
The ADM1073 is designed to control the manner in which a
board’s supply voltage is applied so that harmful transient
currents do not occur and the board can be safely inserted or
removed from a live backplane. Undervoltage, overvoltage, and
overcurrent protection are other features of the part. The
ADM1073 ensures that the input voltage is stable and within
tolerance before being applied to the power module.
The ADM1073 hot swap controller normally resides on a
removable circuit board and controls the manner in which
power is applied to the board upon connection. This is achieved
using a FET, Q1, in the power path (see Figure 31). By
controlling the gate voltage of the transistor, the surge of current
to charge load capacitance can be limited to a safe value when
the board makes connection. The ADM1073 can also reside on
the backplane itself and perform the same function from there.
Figure 32 shows a typical ADM1073 application circuit. When
the plug-in board is inserted into the live backplane, the −48 V
and 0 V lines connect to the live supply. This powers up the
device with the voltage on VIN exceeding VLKO. When the voltage
on the UV pin exceeds the undervoltage rising threshold
(0.868 V), it is now inside the programmed operating voltage
window. It must stay inside this window for the duration of the
power-on reset delay time, tPOR (150 ms).
PLUG-IN BOARD
0V
LIVE
BACKPLANE
–48V
SHDN RESTART
RDROP
R1
R3
LATCHED
R2
R4
CSS
ADM1073
CTIMER
RSENSE
FET
SPLYGD
PWRGD
RDRAIN
VIN+
CLOAD
DC-DC
CONVERTER
VIN–
–48V RTN
R1
R3
R2
R4
CSS
Figure 31. ADM1073 Topology
VEE
RDROP
VIN
OV
UV
SS
TIMER
VCC AND
REFERENCE
GENERATOR
OVERVOLTAGE
DETECTOR
UNDERVOLTAGE
DETECTOR
SOFT START
CONTROL
TIMER CONTROL
SPLYGD
FOLDBACK
AND PWRGD
PWRGD
RDRAIN
DRAIN
VIN
DC-DC
CONVERTER
100mV(MAX)
FAULT TIMER
AND CONTROL
50µA
FET
GATE
SENSE
RSENSE
5 SECOND
OSCILLATOR PWM
VEE
SHUTDOWN
TIMEOUT
5V
3.3V
2.8V
...etc.
GND
RTIMER*
CTIMER SHDN
RESTART
LATCHED
+48V
*RTIMER IS AN OPTIONAL COMPONENT
Figure 32. ADM1073 Application Diagram
Rev. 0 | Page 13 of 24
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