Datasheet

Bridge
Sensor
+VDD
AINP
AINN
VREFN
SW
GND
ADS1231
VREFP
CLK_DETECT
Internal
Oscillator
MUX
ToADC
S
S0 S1
EN
CLKIN
ADS1231
SBAS414D –JULY 2009–REVISED OCTOBER 2013 www.ti.com
LOW-SIDE POWER SWITCH (SW) CLOCK SOURCE
The ADS1231 incorporates an internal switch for use The ADS1231 can use the internal oscillator or an
with an external bridge sensor, as shown in external clock source to accommodate a wide variety
Figure 15. The switch can be used in a return path for of applications. Figure 16 shows the equivalent
the bridge power. By opening the switch, power circuitry of the clock module. The CLK_DETECT
dissipation in the bridge is eliminated. block determines whether an external clock signal is
applied to the CLKIN pin so that the internal oscillator
The switch is controlled by the ADS1231 conversion
is bypassed or activated. When the CLKIN pin
status. During normal conversions, the switch is
frequency is above ~200kHz, the CLK_DETECT
closed (the SW pin is connected to GND). During
circuit shuts down the internal oscillator and passes
standby or power-down modes, the switch is opened
the external clock signal to the ADC. When the
(the SW pin is high impedance). When using the
CLKIN pin frequency is below ~200kHz, the
switch, it is recommended that the negative reference
CLK_DETECT block activates the internal oscillator.
input (VREFN) be connected directly to the bridge
When the internal oscillator is chosen, make sure to
ground terminal, as shown in Figure 15 for best
connect the CLKIN pin to GND.
performance.
Figure 16. Equivalent Circuitry of the Clock
Source
The allowable frequency range for the external clock
signal f
CLKIN
is specified in the Electrical
Characteristics table.
Figure 15. Low-Side Power Switch
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