MAX8728EVKIT Maxim Integrated Products, MAX8728EVKIT Datasheet - Page 5

• Manufacturer Part Number: MAX8728EVKIT
• Description: Display Modules & Development Tools MAX8728 KIT MAX8728 KIT
• Manufacturer: Maxim Integrated Products

Specifications of MAX8728EVKIT

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The MAX8728 EV kit features a capacitive dummy load
of 1500pF (C23) at the VGON output pad to simulate a
panel load to test the switch matrix. Jumper JU3
selects and deselects the dummy load. Table 3 lists
jumper JU3 options.
The MAX8728 EV kit features a method to configure the
VGON discharge path using resistor R13 and jumper
JU4. When CTL is low, GON may be connected to DRN,
allowing VGON to discharge through resistor R13. R13
can be connected to AVDD (through diode D3) or to
PGND using jumper JU4. Table 4 lists the selectable
JU4 jumper options. If VGON’s desired lower level is
greater than AVDD, discharge VGON toward AVDD to
save power. The VGON’s discharge rate can be adjust-
ed by selecting a different value for R13.
The MAX8728 EV kit features an option to select the
operating mode (delay or no delay) for the high-voltage
switches, on the rising edge of the CTL pin, GON con-
nects to SRC. On CTL's falling edge, GON may con-
nect immediately to DRN (no delay), or GON may con-
nect to DRN after a delay set by C17. Jumper JU5
selects the high-voltage switch operating mode for the
MAX8728. Table 5 lists the selectable JU5 jumper
options.
Table 4. Jumper JU4 Functions
(VGON Discharge)
Table 3. Jumper JU3 Functions (LOAD)
Dummy Load for the High-Voltage Switch
LOCATION
(default)
SHUNT
Not installed
LOCATION
Installed
(default)
1-2
2-3
SHUNT
High-Voltage Switch Mode (MODE)
R13 and diode D3
CONNECTED TO
through resistor
_______________________________________________________________________________________
PGND through
resistor R13
DRN PIN
DUMMY LOAD
AVDD
Connected to
Unconnected
VGON
(C23)
VGON Discharge Path
VGON DISCHARGED
Output (VGON)
Testing mode
(no panel)
Normal operation
(panel load)
TOWARD
FUNCTION
PGND
AVDD
EV KIT
MAX8728 Evaluation Kit
The step-down and step-up regulators on the MAX8728
EV kit switch at the same frequency, but are 180
degrees out-of-phase with each other. The MAX8728
switching frequency is selectable among 1.5MHz,
1MHz, and 500kHz by jumper JU6. Table 6 lists the
selectable JU6 jumper options.
Note that jumper JU6 is not installed and is shorted
between pin holes 1 and 4 by a PC board trace. To uti-
lize jumper JU6, cut open the PC board trace between
pin holes 1 and 4, and install a shorting wire between
pin holes 1 and 2 for 1MHz operation, or pin holes 1
and 3 for 500kHz operation.
The EV kit is configured for 1.5MHz operation. Optimum
performance at lower frequencies requires larger
inductor values. Refer to the Step-Down Regulator
Design and Step-Up Regulator Design section in the
MAX8728 data sheet.
The MAX8728 EV kit’s step-down switching regulator’s
output (OUT1) is set to +3.3V by feedback resistors R1
and R2. To generate output voltages other than +3.3V
(from 2V to 3.6V), select different external voltage-
divider resistors, R1 and R2. Refer to the Detailed
Description, Step-Down Regulator section in the
MAX8728 data sheet for instructions on selecting resis-
tors R1 and R2.
Table 5. Jumper JU5 Functions (MODE)
Table 6. Jumper JU6 Functions (FSEL)
(shorted, default)
Not installed
LOCATION
LOCATION
Step-Down Switching-Regulator Output
(default)
SHUNT
Switching Frequency Selection (FSEL)
SHORT
1-2
2-3
1-4
1-3
1-2
Output Voltage Selection
CONNECTED TO
CONNECTED TO
(through resistor
Unconnected
MODE PIN
FSEL PIN
R16)
REF
C17
GND
REF
VL
Voltage (OUT1)
No delay
Delay set by C17
Not allowed
HIGH-VOLTAGE
SWITCH MODE
FREQUENCY
1.5MHz
500kHz
EV KIT
1MHz
5