Datasheet

Evaluates: MAX9924U/MAX9925
MAX9924U MODE A1, A2, B, and C Operation
The MAX9924U EV kit features jumpers JU1–JU5 and
JU7 to configure the VR sensor interface circuit mode
of operation. The circuit can be configured for MODE
A1, A2, B, or C operation. Table 4 lists the various
jumper options for configuring the circuit.
MODE B Operation: Supply a digital PWM signal to the
FILTER and GND pads. The signal must provide a 5V
logic-high frequency in the range of 25kHz to 100kHz.
MODE C Operation: Threshold voltage resistors R1
and R2 must be selected using the following equation.
Refer to the Comparator section and Figure 5 in the
MAX9924/MAX9925 IC data sheet for additional infor-
mation on selecting threshold voltages.
V
TL
= [R2/(R1 + R2)] x V
BIAS
V
TH
= [R1/(R1 + R2 + R14)] x (V_PULL - V
BIAS
) + V
BIAS
where R2 is typically in the range of 50kΩ to 500kΩ,
R14 is 10kΩ, V
BIAS
is the voltage at the MAX9924U
BIAS pin, and V_PULL is the voltage connected to the
V_PULL pad. Refer to the
Mode Selection section in the
MAX9924/MAX9925 IC data sheet for additional infor-
mation on selecting a mode of operation and the
Comparator section for additional information on select-
ing threshold voltages.
COUT and V_PULL
The MAX9924U open-drain comparator output is avail-
able at the COUT PCB pad. The V_PULL PCB pad is
provided to pull up the COUT signal through R14 to the
voltage connected to the V_PULL PCB pad. V_PULL
accepts voltages from 0 to 5.5V.
Evaluating a MAX9925
The MAX9924U EV kit can also be used to evaluate the
MAX9925 IC with externally set gain (IC replacement of
U1 required). Contact the factory to request a free sam-
ple of the MAX9925. Cut open the shorting trace across
R20 and R21 pads before populating the resistors on
these pads. To set the gain to 1V/V, install 100kΩ resis-
tors at R20 and R9 for the IN+ input and 100kΩ resis-
tors at R21 and R10 for the IN- input. Test point TP5 is
provided for probing the pin 3 signal of the MAX9925
IC during evaluation.
MAX9924U Evaluation Kit
4 _______________________________________________________________________________________
Table 4. MODE A1, A2, B, and C Configuration (JU1–JU5, JU7)
MODE
JU1
(R1, R2)
JU2
(BIAS)
JU3
(ZERO_EN)
JU4
(EXT)
JU5
(INT_THRS)
JU7
(SENSOR)
MODE
A1 Open 1&2 Open 1-2 1-2 Installed* A1
A2 Open 2&3 Installed 1-2 2-3 Installed* A2
B Open 1&2 Open 1-3 2-3 Installed* B
C Installed 1&2 Installed 1-4 2-3 Installed* C
* Open for a differential sensor or installed for singled-ended sensors or the triangle-wave generator.