ADM1070ARTZ Analog Devices Inc, ADM1070ARTZ Datasheet - Page 9

• Manufacturer Part Number: ADM1070ARTZ
• Manufacturer: Analog Devices Inc

Specifications of ADM1070ARTZ

• Linear Misc Type: Negative Voltage
• Family Name: ADM1070
• Package Type: SOT-23
• Operating Supply Voltage (min): -18V
• Operating Supply Voltage (max): -80V
• Operating Temperature (min): -40C
• Operating Temperature (max): 85C
• Operating Temperature Classification: Industrial
• Product Depth (mm): 1.6mm
• Product Height (mm): 1.15mm
• Product Length (mm): 2.9mm
• Mounting: Surface Mount
• Pin Count: 6
• Lead Free Status / RoHS Status: Compliant

FUNCTIONAL DESCRIPTION
HOT CIRCUIT INSERTION
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 components on the board.
The ADM1070 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 pro-
tection are other features of the part. The ADM1070 ensures that
the input voltage is stable and within tolerance before being applied
to the dc-to-dc converter, which generates the low voltage levels
required to power the on-board logic. One such converter is the
Artesyn EXQ50. Go to
INITIAL STARTUP
The ADM1070 hot swap controller normally resides on a remov-
able 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. By controlling the gate voltage of
the FET, the surge of current to charge load capacitance can be
limited to a safe value when the board makes connection. Note
that the ADM1070 can also reside on the backplane itself, and
perform the same function from there.
REV. 0
BACKPLANE
BACKPLANE
–48V
LIVE
–48V
LIVE
0V
0V
Figure 2. Circuit Board Connection
R1
R2
R1
R2
Figure 1. Topology
ADM1070
R
www.artesyn.com
SENSE
R
DROP
PLUG-IN BOARD
UV/OV
TMER
ADM1070
V
FET
IN
16k
C
LOAD
SENSE
GATE
for more information.
V
EE
V
V
ARTESYN
IN
IN
EXQ50
+
–
C
LOAD
V
V
TRIM
OUT
OUT
+
–
Q1
R
SENSE
V
OUT
–9–
Figure 2 shows how a plug-in module containing the ADM1070
makes connection to the backplane supply. When the board is
inserted, the –48 V and 0 V lines connect. This powers up the
device with the voltage on V
When the voltage at the UV/OV Pin exceeds undervoltage rising
threshold (V
age window. It must stay inside this window for the duration of
the power-on reset delay time, t
value of C
When the device detects that the supply voltage is valid, it ramps
up the gate voltage until the FET turns on and the load current
increases. The ADM1070 monitors the level of the current flowing
through the FET by sensing the voltage across the external
sense resistor, R
the GATE Pin is actively controlled, limiting the load current.
In this way, the maximum current permitted to flow through the
load is set by the choice of R
If a change in the level of the supply voltage causes UV/OV to
fall below the undervoltage falling threshold of V
above the overvoltage rising threshold of V
drive will be disabled.
BOARD REMOVAL
If the board is removed from a card cage, the voltage at the
UV/OV pin falls to zero (i.e., outside operating range) and the
gate drive is deasserted, turning off the FET.
CONTROLLING THE CURRENT
The ADM1070 features a current limiting function that protects
against short circuits or excessive supply currents. The flow of
current through the load is monitored by measuring the voltage
across the sense resistor, which is connected between the SENSE
and V
1. If the voltage across the sense resistor exceeds the circuit
breaker limit voltage of 88 mV (rising) for the current limit
on time (t
PWM cycle begins. The FET current is linearly controlled at
a maximum of 100 mV/R
t
duration t
given by t
A unique feature of the ADM1070 is the limited consecutive
retry function. An internal fault counter keeps track of the
number of successive PWM cycles that occur. The fault
counter is incremented after every fault is detected. If the
ADM1070 detects seven consecutive current faults, it is appar-
ent that the fault is not a temporary one and the device
latches itself off. The fault counter is cleared if a new t
timeout does not occur within 2
t
LIMITON
LIMITON
EE
Pins. There are three different types of protection offered:
T
.
(see next section). The gate is then disabled for the
timeout.
UVR
ON
LIMITON
OFF
/t
) of 0.91 V, it is now inside the operating volt-
SENSE
. This PWM ratio, which will always be 3%, is
OFF
.
), then a current fault has occurred and the
. When the sense voltage reaches 100 mV,
IN
SENSE
SENSE
exceeding V
POR
.
(via the gate drive) during
, which is dependent on the
t
OFF
OVR
LKO
of the previous
ADM1070
, then the gate
.
UVF
, or rise
ON