ADM3052BRWZ Analog Devices Inc, ADM3052BRWZ Datasheet - Page 11

• Manufacturer Part Number: ADM3052BRWZ
• Description: 58T4518
• Manufacturer: Analog Devices Inc

Specifications of ADM3052BRWZ

• Interface Type: CAN
• No. Of Rx Buffers: 1
• Digital Ic Case Style: SOIC
• No. Of Pins: 16
• Operating Temperature Range: -40°C To +85°C
• Rohs Compliant: Yes
• Number Of Transmitters: 1
• Power Supply Requirement: Dual
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Operating Temperature (max): 85C
• Operating Temperature (min): -40C
• Lead Free Status / Rohs Status: Compliant

Preliminary Technical Data
THERMAL SHUTDOWN
The ADM3052 contains thermal shutdown circuitry that
protects the part from excessive power dissipation during fault
conditions. Shorting the driver outputs to a low impedance
source can result in high driver currents. The thermal sensing
circuitry detects the increase in die temperature under this
condition and disables the driver outputs. This circuitry is
designed to disable the driver outputs when a junction
temperature of 150°C is reached. As the device cools, the drivers
re-enable at a temperature of 140°C.
LINEAR REGULATOR
The linear regulator takes the V+ bus power (ranging between
11V and 25V) and regulates this voltage to 5V, to provide power
to the internal bus-side circuitry (iCoupler isolation, V+sense
and transceiver circuits). The linear regulator uses two
regulation loops to share the power dissipation between the
internal die and an external resistor. This reduces the internal
heat dissipation in the package. The 300Ω external resistor
should be capable of dissipating 750mW of power and have a
tolerance of 1%.
The limitation on the magnetic field immunity of the iCoupler
is set by the condition in which an induced voltage in the
receiving coil of the transformer is large enough to either falsely
set or reset the decoder. The following analysis defines the
conditions under which this may occur. The 3 V operating
condition of the ADM3052 is examined because it represents
the most susceptible mode of operation.
The pulses at the transformer output have an amplitude greater
than 1 V. The decoder has a sensing threshold of about 0.5 V,
thus establishing a 0.5 V margin in which induced voltages can
be tolerated.
The voltage induced across the receiving coil is given by
where:
β is the magnetic flux density (gauss).
N is the number of turns in the receiving coil.
r
Given the geometry of the receiving coil and an imposed
requirement that the induced voltage is, at most, 50% of the
0.5 V margin at the decoder, a maximum allowable magnetic
field can be determined using Figure 12.
MAGNETIC FIELD IMMUNITY
n
is the radius of the n
V
=
⎛
⎜
⎝
−
dt
d
β
⎞
⎟
⎠
∑
π
r
n
2
th
;
turn in the receiving coil (cm).
n
=
1
2 ,
. ,
, . .
N
Rev. PrG | Page 11 of 16
For example, at a magnetic field frequency of 1 MHz, the
maximum allowable magnetic field of 0.2 kgauss induces a
voltage of 0.25 V at the receiving coil. This is about 50% of the
sensing threshold and does not cause a faulty output transition.
Similarly, if such an event occurs during a transmitted pulse and
is the worst-case polarity, it reduces the received pulse from
>1.0 V to 0.75 V, still well above the 0.5 V sensing threshold of
the decoder.
Figure 13 shows the magnetic flux density values in terms of
more familiar quantities, such as maximum allowable current
flow at given distances away from the ADM3052 transformers.
With combinations of strong magnetic field and high frequency,
any loops formed by PCB traces can induce error voltages large
enough to trigger the thresholds of succeeding circuitry. Care
should be taken in the layout of such traces to avoid this
possibility.
Figure 12. Maximum Allowable External Magnetic Flux Density
0.001
1000
0.01
0.01
100
100
0.1
0.1
10
10
1
1
1k
1k
DISTANCE = 5mm
Figure 13. Maximum Allowable Current for
Various Current-to-ADM3052 Spacings
DISTANCE = 100mm
10k
10k
MAGNETIC FIELD FREQUENCY (Hz)
MAGNETIC FIELD FREQUENCY (Hz)
100k
100k
DISTANCE = 1m
1M
1M
10M
10M
ADM3052
100M
100M