UG-1444
EVAL-ADHV4702-1CPZ
User Guide
Rev. 0 | Page 4 of 10
SHUTDOWN FEATURE (SDN CONNECTOR)
The SD pin of the
ADHV4702-1
can be jumped to logic high,
logic low, or can be left floating via the SDN connector on the
EVAL-ADHV4702-1CPZ evaluation board.
The SD pin is left floating at the SDN connector as shipped
from the factory, enabling the amplifier. Pulling the SD pin low
to DGND places the amplifier in a power saving shutdown
mode. When turning the amplifier back on from the shutdown
state, float the SD pin or pull it high.
INPUT CLAMPING DIODES
To protect the amplifier from high dynamic power dissipation,
the EVAL-ADHV4702-1CPZ evaluation board is configured by
default with input clamping diodes (D6 and D7) that clamp the
input differential voltage of the
ADHV4702-1
at a two-diode
forward bias voltage. This input clamping network limits the
drive to the slew boosting circuit, which affects dynamic perfor-
mance such as bandwidth and slew rate. The recommended
part number for the input clamping diodes is SBAV199LT1G.
Removing the input clamping diodes allows the slew boosting
circuit to be fully biased, which maximizes slew rate and
improves settling time significantly. The fully biased slew
boosting circuit requires additional supply current and results
in higher power dissipation during slewing. For reliable
operation, always operate the amplifier within the safe
operating area curve and provide additional heat sinking as
required for the application. Refer to the
ADHV4702-1
data
sheet for more information.
INPUT GUARD RING
The EVAL-ADHV4702-1CPZ evaluation board employs an
electrostatic guard ring on the top layer to reduce printed
circuit board (PCB) surface leakage currents. The guard ring
encircles the noninverting input and must be biased at the same
voltage as the input. The guard ring can be biased using a
voltage source at P3 or connected to the noninverting input by
installing a 0 Ω resistor at R10. Remove the input clamping
diodes (D6 and D7) to ensure the complete enclosure of the
high impedance input node.
THERMAL MONITOR/FLAG (TMP) AND THERMAL
MANAGEMENT
The TMP pin can be used to monitor relative changes in die
temperature. The typical TMP pin voltage at room temperature
is approximately 1.9 V and changes at approximately −4.5 mV/°C.
More precise temperature readings can be achieved through a
single-point (offset) ambient temperature calibration. This
calibration can be accomplished by measuring the TMP pin to
establish the precise voltage corresponding to ambient tempera-
ture. To avoid calibration error due to self heating, power up the
device in shutdown mode (hold SD low at supply turn on) and
maintain it in shutdown mode until the TMP pin voltage is
measured.
The TMP pin can be connected to the SD pin by installing a 0 Ω
resistor at R8 to enable the overtemperature and short-circuit
protection features. Install a resistor at RTEMP to set the thermal
shutdown threshold temperature. Refer to the
ADHV4702-1
data sheet for more information about the temperature monitor
and short-circuit protection.
The ADHV4702-1 evaluation board is designed with an
exposed copper top layer for robust thermal management.
Solder the exposed pad (EPAD) of the package to the copper
layer to ensure optimal thermal dissipation. The top exposed
copper area is connected to the exposed copper ground plane
on the bottom by an array of five thermal vias. In addition, a
heat sink can be attached to the bottom exposed ground plane
to increase the power dissipation capability of the
ADHV4702-1
.
RESISTOR ADJUSTABLE QUIESCENT CURRENT
(RADJ)
The EVAL-ADHV4702-1CPZ evaluation board is configured by
default with a 0 Ω RADJ resistor that fully biases the amplifier
and sets the supply current to 3 mA. Increasing the value of
RADJ reduces the quiescent current, lowering the bandwidth
and slew rate of the amplifier while also reducing quiescent
power dissipation. Refer to the
ADHV4702-1
data sheet for
more information about RADJ.
