Datasheet

Quick Start
Recommended Equipment
• +4.5V to +5.5V, 5A DC power supply
• One voltmeter
Procedure
The MAX8784 EV kit is fully assembled and tested.
Follow the steps below to verify board operation.
Caution: Do not turn on the power supply until all
connections are completed:
1) Verify that a shunt is installed across jumper JU1 (EV
kit ON).
2) Verify that no shunt is installed across jumper JU2
(VGON internally connected to DRN).
3) Verify that a shunt is installed across pins 1-2 of
jumper JU3 (VGON discharges toward AVDD).
4) Verify that no shunt is installed across jumper JU4
(VGON is not connected to the capacitive dummy
load C17).
5) Verify that no shunt is installed across jumper JU5
(high-voltage stress mode OFF).
6) Connect the positive terminal of the power supply to
the VIN pad on the EV kit. Connect the negative ter-
minal of the power supply to the PGND pad next to
the VIN pad.
7) Turn on the power supply and set the supply to +5V.
8) Verify that the step-up switching regulator output
(AVDD) is +14V.
9) Verify that the gate-on supply (POUT) is +28V.
10) Verify that the gate-off supply (VGOFF) is -9V.
11) Verify that the op-amp outputs (OUT1, OUT2, and
OUT3) are +7V.
Detailed Description
The MAX8784 EV kit contains a step-up switching regu-
lator, a positive charge pump, a negative charge
pump, three high-current op amps, and a high-voltage
switch matrix. The EV kit is configured to operate from a
DC power supply between +4.5V to +5.5V that can pro-
vide at least 5A. The EV kit’s input-voltage range can
be extended to +4V to +5.5V at slightly lower load cur-
rents. The MAX8784 step-up regulator operates at a
switching frequency of 1.2MHz.
The step-up switching regulator (AVDD) generates a
+14V output and provides at least 700mA. The step-up
switching regulator output voltage can be adjusted
from +7V to +19V by replacing feedback resistors R1
and R2 (refer to the
Design Procedure, Step-Up
Regulator, Output Voltage Selection section in the
MAX8784 data sheet). Operation at significantly higher
output voltages may reduce the available output cur-
rent and may require changes in component values or
component voltage rating.
The step-up switching regulator’s startup delay time is
configured by replacing capacitor C9. Refer to the
Power-Up Sequence section in the MAX8784 data
sheet for additional details.
The gate-on (POUT) supply consists of a two-stage
positive charge pump that generates +28V and pro-
vides greater than 50mA. This output can be adjusted
from approximately +AVDD to nearly +3xAVDD by
replacing feedback resistors R3 and R4 (refer to the
Design Procedure, Charge-Pump Regulators, Output
Voltage Selection
section in the MAX8784 data sheet).
The positive charge-pump regulator’s startup delay
time is configured by replacing capacitor C8. Refer to
the Positive Charge-Pump Regulators and Power-Up
Sequence
sections in the MAX8784 data sheet for
additional details.
The VGOFF supply consists of a negative charge pump
that generates -9V and provides greater than 50mA.
This output can be adjusted from approximately 0V to
-AVDD by replacing feedback resistors R5 and R6 (refer
to the
Design Procedure, Charge-Pump Regulator,
Output Voltage Selection section in the MAX8784
data sheet).
The MAX8784 provides three high-current op amps that
can each source or sink 180mA. The outputs of the
amplifiers are configured for +7V (AVDD/2).
The MAX8784 contains two high-voltage switches that
operate in a complementary fashion. One of the switch-
es provides a connection between the POUT and GON
pins. The other switch provides a connection between
the GON and DRN pins. The switches can be con-
trolled by an external TTL logic signal connected to the
CTL pad.
When CTL is high, GON is connected to POUT, charg-
ing VGON to the voltage of the positive charge pump at
the POUT pad. When CTL is low, GON is connected to
DRN, allowing VGON to discharge toward AVDD
(through resistor R19 and jumper JU3), or toward
PGND (through resistor R19 and jumper JU3). The
MAX8784 EV kit also features a capacitive dummy load
of 1500pF (C17) at the VGON output pad that can be
connected through jumper JU4 to simulate a panel load
to test the switch matrix.
Evaluates: MAX8784
MAX8784 Evaluation Kit
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