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General Description
The MAX1724 evaluation kit (EV kit) is a fully assembled
and tested surface-mount circuit board that contains
two separate boost switching-regulator circuits. The
left-side circuit contains a MAX1724 with a preset 3.3V
output. Other preset voltages of 2.7V, 3.0V, or 5.0V are
also available. The right-side circuit contains a
MAX1722, which has an adjustable output voltage. This
circuit’s output is set for 3.6V. All devices regulate with
input voltages from 0.91V to VOUT, making them ideal
for 1- or 2-cell alkaline and NiMH battery applications.
The right-side circuit may also be used to evaluate the
MAX1723, which features a shutdown (SHDN) mode.
The MAX1722/MAX1724 has a BATT pin, which lowers
the guaranteed startup voltage from 1.2V to 0.91V.
The MAX1722/MAX1723/MAX1724 feature synchronous
rectification and ultra-low (1.5µA typ) quiescent current
for maximum efficiency and long battery life. Operation
up to 200kHz allows tiny surface-mount components.
Features
♦0.91V to VOUT Input Voltage Range
♦Two Complete Boost Circuits
3.3V Fixed (MAX1724)
3.6V Adjustable Output (MAX1722)
♦Up to 50mA Output from a 1-Cell Input
Up to 100mA Output from a 2-Cell Input
♦1.5µA Quiescent Current from VOUT
♦Up to 90% Efficiency with Synchronous
Rectification
♦Switching Frequency Up to 200kHz
♦All Surface-Mount Design
♦Fully Assembled and Tested Board
Quick Start
The MAX1724 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.
3.3V Output (left side):
1) Connect a 0.91V to 3.3V supply to the VBATT pad.
Connect the supply ground to the GND pad.
2) Connect a voltmeter to the VOUT pad.
3) Verify there is a shunt across pins 1 and 2 of
jumper JU1 (SHDN), thus enabling the MAX1724.
4) Turn on the power supply and verify that the output
is at 3.3V.
3.6V Output (right side):
1) Connect a 0.91V to 3.6V supply to the VBATT pad.
Connect the supply ground to the GND pad.
2) Connect a voltmeter to the VOUT pad.
3) Verify there is a shunt across pins 1 and 2 of jumper
JU2 to connect BATT to VBATT for the MAX1722.
4) Turn on the power supply and verify that the output
is at 3.6V.
For instructions on selecting feedback resistors for
other output voltages, see Evaluating Other Output
Voltages (Right Side).
Evaluates: MAX1722/MAX1723/MAX1724
MAX1724 Evaluation Kit
________________________________________________________________ Maxim Integrated Products 1
19-2076; Rev 1; 5/05
Component List
PART
MAX1724EVKIT 0°C to +70°C
TEMP RANGE IC PACKAGE
THIN SOT23-5
Ordering Information
Note: Quantities are for both circuits.
DESIGNATION QTY DESCRIPTION
C1–C4 4
10µF, 16V X7R ceramic capacitors
TDK C3225X7R1C106MT or
Murata GRM32DR71C106MA
D1 0 Not installed
L1, L2 2 10µH inductors
Sumida CDR43-100MC
R1 1 2MΩ ±1% resistor (0805)
Venkel CR0805-10W-2004FT
R2 1 1.02MΩ ±1% resistor (0805)
Venkel CR0805-10W-1024FT
U1 1 M axi m M AX 1724E Z K33 ( 5- p i n TH IN
S OT23, top m ar k AD Q J)
U2 1 Maxim MAX1722EZK (5-pin THIN
SOT23, top mark ADQF)
JU1, JU2 2 3-pin headers
None 2 Shunts JU1, JU2
None 1 MAX1724 PC board
Evaluates: MAX1722/MAX1723/MAX1724
MAX1724 Evaluation Kit
2 _______________________________________________________________________________________
Detailed Description
The MAX1724 EV kit contains two separate boost
switching-regulator circuits. The left-side circuit
(MAX1724) supplies a preset 3.3V output. The right-
side circuit (MAX1722) supplies an adjustable 3.6V out-
put, but can also be set from 2.0V to 5.5V. Both circuits
regulate with input voltages from 0.91V to VOUT, but
can accept higher input voltages (below 5.5V) if it is
acceptable for the output voltage to rise above the set
VOUT. Output current for both circuits is 50mA with a
1.2V input, and 100mA for a 2.4V input.
The 3.6V output voltage (right side) can also be adjust-
ed from 2.0V to 5.5V using external resistors R1 and
R2. The input voltage ranges from 0.91V to (VOUT)
when operating from a DC source.
The MAX1724 boost converter (left side) features a
0.1µA shutdown mode.
Jumper Selection
MAX1724 Circuit (Left Side)
The MAX1724 EV kit’s shutdown mode reduces the IC’s
quiescent current to 0.1µA (typ), preserving battery life.
Jumper JU1 selects the shutdown mode for the
MAX1724. Table 1 lists the MAX1724 jumper options.
MAX1722 Circuit (Right Side)
When jumper JU2 on the right-side circuit is used with a
MAX1722, pins 1 and 2 must be connected together so
that BATT is connected to the battery input (VBATT).
When the right-side circuit is used to evaluate a
MAX1723, see Evaluating the MAX1723 section. Table
2 lists the MAX1722 jumper options.
3.6V Output (right side):
1) Connect a 0.91V to 3.6V supply to the VBATT pad.
Connect the supply ground to the GND pad.
2) Connect a voltmeter to the VOUT pad.
3) Verify there is a shunt across pins 1 and 2 of
jumper JU2 to connect BATT to VBATT for the
MAX1722.
4) Turn on the power supply and verify that the output
is at 3.6V.
For instructions on selecting feedback resistors for
other output voltages, see Evaluating Other Output
Voltages (Right Side).
Evaluating Other Output Voltages
(Right Side)
The MAX1722 output is set to 3.6V by feedback resis-
tors R1 and R2. To generate output voltages other than
3.6V (2.0V to 5.5V), select different external voltage-
divider resistors (R1, R2). Refer to the Setting the
Output Voltage section in the MAX1722/MAX1723/
MAX1724 data sheet for instructions on selecting R1
and R2 for the MAX1722/MAX1723.
Evaluating the MAX1723
The MAX1723 can be evaluated using the MAX1722
circuit (right side). Replace the MAX1722 with a
MAX1723EZK. Diode D1 (Motorola MBR0520L or equiv-
SHDN PIN MAX1724 OUTPUT
1-2 Connected to
VBATT
MAX1724 enabled,
VOUT = 3.3V
2-3 Connected to GND Shutdown mode,
VOUT = VBATT - VDIODE
SHUNT
LOCATION
Table 1. MAX1724 Jumper JU1 Functions
SHUNT LOCATION BATT PIN
1-2 Connected to VBATT
2-3 Not allowed
Table 2. MAX1722 Jumper JU2 Functions
Component Suppliers
SUPPLIER PHONE FAX WEBSITE
Murata 814-237-1431 814-238-0490 www.murata.com
Sumida 847-956-0666 847-956-0702 www.sumida.com
TDK 847-803-6100 847-390-4405 www.component.tdk.com
Venkel 512-794-0081 512-794-0087 www.venkel.com
Note: Please indicate that you are using the MAX1724 when contacting component suppliers.
alent) may be necessary for low-voltage startup. Refer
to the Low-Voltage Startup Oscillator section in the
MAX1722/MAX1723/MAX1724 data sheet for additional
instructions on selecting D1.
The MAX1723 circuit features a shutdown mode that
reduces current to 0.1µA (typ), preserving battery life.
Jumper JU2 selects the MAX1723 shutdown mode.
Table 3 lists the MAX1723 jumper options.
Evaluates: MAX1722/MAX1723/MAX1724
MAX1724 Evaluation Kit
_______________________________________________________________________________________ 3
Table 3. MAX1723 Jumper JU2 Functions
BATT
MAX1724
GND
L1
10µH
VBATT
0.91V TO VOUT
GND
2
1
3
SHDN
LX
1
2
3
5
4
OUT
SHDN
3.3V
VOUT
GND
C2
10µF
16V
C1
10µF
16V
U1
JU1
Figure 1. MAX1724 EV Kit Left-Side Circuit Schematic
BATT
MAX1722
GND
L2
10µH
VBATT
0.91V TO VOUT
GND JU2 2
1
3LX
1
2
3
5
4
OUT
FB
VOUT
3.6V
GND
R1
2.00MΩ
D1
(OPEN)
R2
1.02MΩ
C3
10µF
16V
C4
10µF
16V
U2
Figure 2. Right-Side Circuit Schematic for MAX1722 and
MAX1723 Evaluation
SHUNT
LOCATION SHDN PIN MAX1723 OUTPUT
MAX1723 enabled,
VOUT = 3.6V
Connected to
VBATT
1-2
2-3 Connected to GND Shutdown mode,
VOUT = VBATT - VDIODE
Evaluates: MAX1722/MAX1723/MAX1724
MAX1724 Evaluation Kit
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
4_____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2005 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products, Inc.
Figure 5. MAX1724 EV Kit PC Board Layout—Solder Side
Figure 3. MAX1724 EV Kit Component Placement Guide—
Component Side
Figure 4. MAX1724 EV Kit PC Board Layout—Component Side
