Datasheet
Quick Start
Recommended Equipment
• 2.7V to 5.5V, 2A DC power supply
• One voltmeter
Procedure
The MAX1889 EV kit is fully assembled and tested.
Follow these steps to verify board operation. Do not
turn on the power supply until all connections are
completed:
1) Verify that there are no shunts across jumpers
JU1 (SHDN), JU2 (FREQ), JU3, JU4, and JU8.
2) Verify that a shunt is across pins 1 and 2 of JU7.
3) Verify that a shunt is across pins 1 and 3 of JU6.
4) Verify that a shunt is across pins 1 and 4 of JU5.
5) Connect the positive terminal of the input power
supply to the PIN pad. Connect the negative termi-
nal of the input power supply to the PGND pad.
6) Turn on the power supply and verify that the step-
up regulator output (VBST) is 9V.
7) Verify that the positive linear-regulator output (VPL)
is 20V.
8) Verify that the negative linear-regulator output (VNL)
is -7V.
For instructions on selecting the feedback resistors for
other output voltages, see the Output Voltage Selection
section.
Detailed Description
The MAX1889 EV kit contains a step-up switching regu-
lator and two linear-regulator controllers. It operates
from a DC power supply between 2.7V and 5.5V. The
switching frequency is selectable between 500kHz and
1MHz. The input and outputs of the EV kit are protected
against overload. The EV kit features a shutdown mode
for maximum battery life.
As configured, the step-up switching regulator generates
a 9V output and can provide at least 200mA of current to
the output. The step-up switching-regulator output volt-
age can be adjusted from the input voltage up to 13V
with resistors (see the Output Voltage Selection section).
As configured, the positive charge pump uses two of the
three charge-pump stages to generate approximately
24V and can provide greater than 10mA. The output is
post-regulated to 20V using a linear-regulator controller
and an external bipolar pass transistor. The positive linear
regulator’s output can be adjusted between 1.25V and
28V or, with additional circuitry, to even higher voltages
(refer to the Linear-Regulator Controllers section in the
MAX1889 data sheet).
As configured, the negative charge pump uses one of
the three charge-pump stages to generate approxi-
mately -7.6V and can provide greater than 10mA. The
output is post-regulated to -7V using a linear-regulator
controller and an external bipolar pass transistor. The
negative linear regulator’s output can be adjusted
between 0 and -22V or, with additional circuitry, to even
lower voltages (refer to the Linear-Regulator Controllers
section in the MAX1889 data sheet).
The EV kit includes input-current overload protection
that shuts down the circuit if the input current exceeds
a threshold for longer than 64ms. The threshold is set
by resistor-divider R1, R2, R19, R20, and the R
DS(ON)
of MOSFET P1 or P2. Refer to the Setting the Input
Overcurrent Threshold section in the MAX1889 data
sheet for further details. The EV kit also includes output
overload protection that shuts down the circuit if any of
the output voltages drop below approximately 80% of
their nominal value for longer than 64ms.
Jumper Selection
Shutdown Mode
The MAX1889 EV kit features a shutdown mode that
reduces the MAX1889 quiescent current to less than
1µA. The 2-pin jumper, JU1, selects the shutdown
mode for the MAX1889 EV kit. Table 1 lists the selec-
table jumper options.
Caution: Do not connect an external controller to
the SHDN pad while a shunt is on JU1 since the
external controller can be damaged.
Frequency Mode
The MAX1889 EV kit features an option to choose the
switching frequency. JU2 selects the frequency mode for
the MAX1889 EV kit. Table 2 lists the selectable jumper
options. The EV kit is configured for 1MHz operation.
Optimum performance at 500kHz requires a larger induc-
tor value (refer to the Inductor Selection section in the
MAX1889 data sheet.)
Positive Charge Pump
The positive charge pump of the MAX1889 EV kit features
an option to cascade up to three stages of charge
pumps. Each stage of the charge pump can be powered
from INPUT, VBST, or the previous stage. JU8, JU7, and
JU6 configure the number of stages and select the
voltage source for the positive charge pump on the
MAX1889 EV kit. Tables 3, 4, and 5 list the jumper
options. The default configuration of the positive charge
pump of the MAX1889 EV kit is a two-stage charge pump
powered from VBST as indicated in Tables 4 and 5. Refer
to the Charge Pumps section of the MAX1889 data sheet
for information on selecting a charge-pump configuration.
Evaluates: MAX1889
MAX1889 Evaluation Kit
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