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Data Sheet
AD5700/AD5700-1
Rev. F | Page 15 of 24
option is beneficial where cost or board space is a large concern
because it removes the need for multiple external components.
This configuration achieves an 8 kV ESD HBM rating but
requires extra external protection circuitry for EMC and surge
protection purposes if used in harsh industrial environments.
CLOCK CONFIGURATION
tions to allow the optimal trade-off between cost and power:
External crystal
CMOS clock input
The CLK_CFG0, CLK_CFG1, and XTAL_EN pins configure
can also provide a clock output at CLKOUT (for more details,
External Crystal
The typical connection for an external crystal (ABLS-3.6864MHZ-
consumption and to minimize stray capacitances, connections
between the crystal, capacitors, and ground should be made as
crystal vendors for recommended load information and crystal
performance specifications.
Figure 25. Crystal Oscillator Connection
The ABLS-3.6864MHZ-L4Q-T crystal oscillator data sheet
recommended two 36 pF capacitors. Because the crystal current
consumption is dominated by the load capacitance, in an effort
to reduce the crystal current consumption, two 16 pF capacitors
still functioned as expected, even with the resulting reduction in
frequency performance from the crystal due to the smaller
capacitance values. Crystals are available that support 16 pF
capacitors. It is recommended to consult the relevant crystal
manufacturers for this information.
CMOS Clock Input
A CMOS clock input can also be used to generate a clock for the
clock source to the XTAL 1 pin, and leave XTAL2 open circuit
Figure 26. CMOS Clock Connection
Consuming typically 218 A, the low power, internal, 0.5 %
precision RC oscillator, available only on th
eAD5700-1, has an
oscillation frequency of 1.2288 MHz. To use this mode, tie the
XTAL1 pin to ground and leave the XTAL2 pin open circuit
Figure 27. Internal Oscillator Connection
CLKOUT
If using the crystal oscillator, this clock output can be
configured as a 3.6864 MHz, 1.8432 MHz, or 1.2288 MHz
buffer clock.
If using a CMOS clock, no clock output can be configured
at the CLKOUT pin.
If using the internal RC oscillator, this clock output is only
available as a 1.2288 MHz buffer clock.
The amplitude of the clock output depends on the IOVCC level;
therefore, the clock output can be in the range of 1.71 V p-p to
increases the current consumption of the device. This increase
is due to the current required to drive any load at the CLKOUT
pin, which should not be more than 30 pF.
This capacitance should be minimized to reduce current
consumption and provide the clock with the cleanest edges.
The additional current drawn from the IOVCC supply can be
calculated using the following equation:
I = C × V × f
10435-
021
HART
NETWORK
680pF
2.2nF
HART_OUT
HART_IN
ADC_IP
AD5700/
AD5700-1
10435-
022
ABLS-3-6864MHZ-L4Q-T
36pF
X
TA
L1
X
TA
L2
AD5700/AD5700-1
10435-
027
X
TA
L1
X
TA
L2
AD5700/AD5700-1
10435-
028
X
TA
L1
X
TA
L2
AD5700-1