MAX1620EVKIT Maxim Integrated, MAX1620EVKIT Datasheet - Page 2

• Manufacturer Part Number: MAX1620EVKIT
• Description: Power Management IC Development Tools Evaluation Kit for the MAX1620 MAX1621
• Manufacturer: Maxim Integrated
• Series: MAX1620, MAX1621r

Specifications of MAX1620EVKIT

• Output Current: 150 uA

MAX1620 Evaluation Kit
The MAX1620 EV kit converts a +1.8V to +12V battery
voltage to a +12.5V to +23.5V LCD backplane bias volt-
age for currents up to 20mA. The output voltage can be
adjusted with the on-chip DAC, allowing digital software
control of the bias voltage. Up/down digital signaling
adjusts the DAC.
The output voltage is set with a voltage divider to the
feedback pin (FB). It can be adjusted with an internal
DAC summing current into FB through an external
resistor. The 5-bit DAC is controlled with a user-pro-
grammable up/down counter. The MAX1620 controls
the DAC counter with the UP and DN pins. A rising
edge on UP increases the output voltage; a rising edge
on DN decreases the output voltage. Holding both UP
and DN high resets the output voltage to mid-range.
Refer to the Output Voltage Control section in the
MAX1620/MAX1621 data sheet for more information on
controlling the MAX1620/MAX1621 output voltage.
Controlling the LCD Using POK and
POK can be used to turn off a positive LCD bias volt-
age when V
from V
LCDON, which pulls low when V
LCDON drives an external PNP transistor, Q1, switch-
ing a positive V
saturation voltage at the required load current. R6 limits
the base current in Q1. R7 is used to turn off Q1 when
LCDON is floating. R6 and R7 can be the same value.
Refer to the Controlling the LCD Using POK and
LCDON section in the MAX1620/MAX1621 data sheet
for instructions on selecting resistors R1, R2, R6, and
R7.
The MAX1620 EV kit features a shutdown mode that
reduces the MAX1620 quiescent current to 14µA to
preserve battery life. The two-pin header JU8 selects
the shutdown mode. Table 1 lists the selectable jumper
options.
This EV kit is shipped with the MAX1620’s polarity pin
(POL) tied to V
age. A boost topology is used, and the feedback regu-
lation point is 1.5V. Refer to the Output Adjustment
section in the MAX1620/MAX1621 data sheet for
instructions on selecting the feedback resistors.
2
_______________Detailed Description
_______________________________________________________________________________________
BATT
BATT
to POK controls the open-drain output,
IN
OUT
for converting to a positive output volt-
is too low. A resistor-divider (R1-R2)
to the LCD. Choose a PNP with low
Output Voltage Control
Positive Output Voltage
POK
Jumper Selection
> 1V.
Shutdown Mode
LCDON
If a negative output voltage is desired, connect the
MAX1620’s POL pin to ground using jumper JU3. In
this configuration, the error amplifier’s output is inverted
to provide the correct feedback polarity. The feedback
regulation point is 0V. To modify the EV kit for a nega-
tive output voltage:
1) Cut the PC board trace to open jumpers JU1, JU4,
2) Short jumpers JU2, JU6, and JU7 with a piece of
3) Place the JU3 shunt across pins 2 and 3 (Table 2)
4) Install supplied components D2, D3, C4, and C7.
Table 3 summarizes jumper JU1–JU7 settings.
To evaluate the MAX1621, remove the MAX1620 IC
and resistors R8, R9, and R10.
Table 1. Jumper JU8 Settings
Table 2. Jumper JU3 Settings
Table 3. Jumper JU1– JU7 Settings
LOCATION
and JU5.
wire.
LOCATION
SHUNT
JUMPER
SHUNT
1 and 2
2 and 3
On
Off
JU1
JU2
JU3
JU4
JU5
JU6
JU7
Connected
Connected
S S H H D D N N PIN
Connected to GND
to GND
Connected to VIN
to VIN
POSITIVE OUT
Short 1 and 2
POL PIN
Evaluating the MAX1621
Open
Open
Open
Short
Short
Short
Negative Output Voltage
Shutdown mode, V
V
MAX1620 enabled,
V
BATT
OUT
MAX1620 OUTPUT
= +17.8V
, V
MAX1620 OUTPUT
Positive output,
V
Negative output,
V
OUTSW
OUT
OUT
NEGATIVE OUT
Short 2 and 3
= +17.8V
= -16.7V
Open
Open
Open
Short
Short
Short
= float
OUT
=