ADM1073 Analog Devices, ADM1073 Datasheet - Page 16

• Manufacturer Part Number: ADM1073
• Description: -48 V Full Feature Hot Swap Controller
• Manufacturer: Analog Devices

Specifications of ADM1073

• I Control Accuracy %: 3%
• Other Inputs: RESTARTb,SHDNb
• Other Outputs: LATCHEDb,PWRGDb,SPLYGDb
• Package: 14-ld TSSOP
• Vin Min (v): -18V
• Vin Max (v): -80V
• Uv & Ov Detection: UV pin, OV pin

ADM1073
DRAIN
Analog input fed by a resistor connected to the drain of the
FET. This pin is clamped to go no higher than 4 V with respect
to V
that, if it falls below 2 V, the PWRGD output can be set. Above
the 4 V level, the current into the pin is detected and used to
modulate the maximum on-time for the linear FET driver. This
is done by summing a proportion of the drain input current
with the charging current for the TIMER timing capacitor,
thereby reducing the allowable on-time.
PWRGD
Output to indicate when the load capacitor is fully charged.
This is an open collector output with internal pull-up to V
When a normal startup is initiated, the PWRGD output is
latched low when the DRAIN pin falls below 2 V. The latch is
reset, if either the input supply goes out of range or a current
limit time-out event occurs. The second of these cases ensures
that, if a voltage step of greater than 2 V is presented at the
input, the PWRGD flag does not go high while the load
capacitor is being charged up to the additional voltage.
LATCHED
Output to indicate when the device has completed the maxi-
mum number (7) of PWM cycles. This is an open collector
output with an internal current source pull-up. If this PWM
time-out event occurs, the GATE pin is latched low and the
LATCHED output is set low. This condition can then be reset
by either a power cycling event or a low signal to either the
SHDN input or the RESTART input. By connecting the
LATCHED signal directly to SHDN , the device can effectively
be put into a continuous PWM mode. By connecting the
LATCHED signal directly to RESTART , the device can
effectively be put into autoretry mode, with a 5-second cooling
period.
SPLYGD
Output to indicate when the input supply is within the pro-
grammed voltage window. This is an open collector output with
an internal pull-up current source. For very large capacitive
loads where multiple FETs and controllers are required to meet
the inrush requirements, this output can be used to drive
directly into the UV pin of a second controller. This allows the
second FET to start 1 ms after the first one, with the added
advantage that the input supply UV detection is done on one
controller only. The SPLYGD output is asserted only when the
ADM1073 is not in reset mode.
RESTART
Edge-triggered input. Allows the user to remotely command a
5-second shutdown and restart of the hot swap function,
effectively simulating a board removal and replacement. The
EE.
Below this level, the voltage on the pin is monitored so
IN
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Rev. A | Page 16 of 24
shutdown function is triggered by a low pulse of at least 5 µs at
the pin. This pin has an internal pull-up of approximately 6 µA,
allowing it to be driven by an open collector pull-down output
or a push-pull output. The input threshold is 1.5 V.
SHDN
Level-triggered input. Allows the user to command a shutdown
of the hot swap function. When this input is set low, the GATE
output is switched to V
internal pull-up of approximately 6 µA, allowing it to be driven
by an open collector pull-down output or a push-pull output.
The input threshold is 1.5 V.
UNDERVOLTAGE/OVERVOLTAGE DETECTION
The ADM1073 incorporates dual pin undervoltage and
overvoltage detection, with a programmable operating voltage
window. When the voltage on the UV pin falls below the UV
falling threshold or the voltage on the OV pin rises above the
OV rising threshold, a fault signal is generated that disables the
linear current regulator and results in the GATE pin being
pulled low. The voltage fault signal is time filtered so that faults
of a duration less than the UV glitch filter time (0.6 ms) and OV
glitch filter time (5 µs) do not force the gate drive low. The filter
operates only on the faulting edge, that is, on a high-to-low
transition on the undervoltage monitor and on a low-to-high
transition on the overvoltage monitor.
The operating voltage window is determined by selecting the
resistor ratios R1/R2 and R3/R4. These resistor networks form
two resistor dividers that generate the voltages at the UV and
OV pins, which are proportional to the supply voltage. By
choosing these ratios carefully, the user can program the
ADM1073 to apply the supply voltage to the load only when it is
within specific thresholds. Note that 1% tolerance resistors
should always be used to maintain the accuracy of the pro-
grammed thresholds.
–48V RTN
–48V IN
R1
R2
R3
R4
Figure 33. Undervoltage and Overvoltage Circuitry
OV
UV
ADM1073
(Standard 4-Resistor Configuration)
V
IN
868mV
1.93V
EE
to turn the FET off. This pin has an
OVERVOLTAGE
UNDERVOLTAGE
DETECTOR
DETECTOR
FET DRIVE
ENABLE
Data Sheet
SPLYGD