Datasheet

Dummy Load for the High-Voltage
Switch Output (VGON)
The MAX8784 EV kit features a capacitive dummy load
of 1500pF (C17) at the VGON output pad to simulate a
panel load to test the switch matrix. When testing with
an LCD panel, disconnect the dummy load. Jumper
JU4 connects and disconnects the dummy load. Table
4 lists the selectable JU4 jumper options.
High-Voltage Stress Mode (HVS)
The MAX8784 EV kit features an option to increase the
output voltage of the step-up switching regulator and
the positive charge pump, to stress test the display
panel during production. Since the op-amp inputs are
derived from the step-up converter output (AVDD), their
output voltages increase when AVDD increases.
Jumper JU5 selects the high-voltage-stress mode for
the MAX8784. Table 5 lists the selectable JU5
jumper options.
Output Voltage Selection
Step-Up Switching Regulator
Output Voltage (AVDD)
The MAX8784 EV kit’s step-up switching-regulator out-
put (AVDD) is set to +14V by feedback resistors R1
and R2. To generate output voltages other than +14V
(from +7V to +19V), select different voltage-divider
resistors. Operation at significantly higher output volt-
ages may reduce the available output current and may
require changes in component values or voltage rating
for capacitors C3 and C4. Refer to the Design
Procedure, Step-Up Regulator, Output Voltage Selection
section in the MAX8784 data sheet for instructions on
selecting resistors R1 and R2.
Positive Charge-Pump Output (POUT)
The positive charge-pump output (POUT) is set to +28V
by voltage-divider resistors R3 and R4. To set POUT to
other voltages (up to nearly +3xAVDD, limited to +35V)
select different voltage-divider resistors. Refer to the
Design Procedure, Charge-Pump Regulator, Output
Voltage Selection
section in the MAX8784 data sheet
for instructions on selecting resistors R3 and R4.
Negative Charge-Pump Output (VGOFF)
The negative charge-pump output (VGOFF) is set to
-9V by voltage-divider resistors R5 and R6. To set
VGOFF to other voltages (from 0V to nearly -AVDD),
select different voltage-divider resistors. Refer to the
Design Procedure, Charge-Pump Regulator, Output
Voltage Selection section in the MAX8784 data sheet
for instructions on selecting resistors R5 and R6.
Op-Amp Outputs (OUT1, OUT2, and OUT3)
The op-amp outputs (OUT1, OUT2, and OUT3) are set
to +7V by voltage-divider resistors R7–R12. To set the
outputs to other voltages (from 0V to AVDD), select dif-
ferent voltage-divider resistors.
Evaluates: MAX8784
MAX8784 Evaluation Kit
_______________________________________________________________________________________ 5
Table 4. JU4 Jumper Selection
(Dummy Load)
SHUNT POSITION VGON EV KIT FUNCTION
Installed Connected to C17 Testing mode
Not installed*
Not connected
to C17
Normal operation
* Default position.
Table 5. JU5 Jumper Selection (HVS)
SHUNT POSITION
HVS PIN
CONNECTED TO
OPERATING
MODE
Installed VIN
High-voltage-
stress mode
Not installed*
GND (through
resistor R13)
Normal mode
* Default position.