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19-1307; Rev 0a; 11/97
MAX1672 Evaluation Kit
_______________General Description
The MAX1672 evaluation kit (EV kit) integrates a stepup switching converter with a linear-regulator output to provide step-up/down voltage conversion. It accepts a 1.8V to 11V input and converts it to a 3.3V or 5V output for currents up to 300mA. The EV kit is optimized for battery applications where the input varies above and below the regulated output voltage. It provides ultra-low quiescent current and high efficiency for maximum battery life. Another benefit of the low-dropout linear postregulator is that it reduces high-frequency ripple. The MAX1672 EV kit is a fully assembled and tested surface-mount circuit board. With minimal modification, it can also be used to evaluate other output voltages. Additional pads on the board accommodate external feedback resistors for setting different output voltages.
____________________________Features
o Step-Up/Down Voltage Conversion o 1.8V to 11V Input Range o 3.3V or 5V Selectable Output Voltage o Adjustable Output Voltage (1.25V to 5.5V) o Load Disconnects from Input in Shutdown o Up to 300mA Output Current o No External FETs Required o 0.1A Typical IC Shutdown Current o Low-Battery Comparator o 16-Pin QSOP Package (same footprint as 8-pin SO) o Surface-Mount Components o Fully Assembled and Tested
Evaluates: MAX1672
____________________Component List
DESIGNATION QTY C1, C2 C3, C5, C6, C7 C4 2 DESCRIPTION 100F, 16V, low-ESR tantalum capacitors AVX TPSE107M016R0100 or Sprague 593D107X0016E2W 0.1F ceramic capacitors 10F, 10V tantalum capacitor Sprague 595D106X0010A2T 1A, 30V Schottky diode Motorola MBRS130LT3 or International Rectifier 10BQ40 10H inductor Sumida CD54-100 Not installed 1M, 5% resistor MAX1672EEE (QSOP-16) 3-pin headers Shunts MAX1672 PC board MAX1672 data sheet
______________Ordering Information
PART MAX1672EVKIT TEMP. RANGE 0C to +70C BOARD TYPE Surface Mount
4 1
______________Component Suppliers
SUPPLIER AVX Coilcraft Coiltronics Dale-Vishay International Rectifier Motorola Sprague Sumida Vishay/Vitramon PHONE (803) 946-0690 (708) 639-6400 (561) 241-7876 (402) 564-3131 (310) 322-3331 (602) 303-5454 (603) 224-1961 (708) 956-0666 (203) 268-6261 FAX (803) 626-3123 (708) 639-1469 (561) 241-9339 (402) 563-6418 (310) 322-3332 (602) 994-6430 (603) 224-1430 (708) 956-0702 (203) 452-5670
D1
1
L1 R1-R4 R5 U1 JU1-JU4 None None None
1 0 1 1 4 4 1 1
Note: Please indicate that you are using the MAX1672 when contacting these component suppliers.
________________________________________________________________ Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. For small orders, phone 408-737-7600 ext. 3468.
MAX1672 Evaluation Kit Evaluates: MAX1672
_________________________Quick Start
The MAX1672 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) Connect a +1.8V to +11V supply voltage to the VIN pad. Connect ground to the GND pad. 2) Connect a voltmeter to the VOUT pad. 3) Verify that all other shunts are across pins 1 and 2 of jumpers JU1-JU4. 4) Turn on the power supply and verify that the output voltage is 3.3V. For a 5V output, remove the shunt from JU1 pins 1 and 2, and place it across pins 2 and 3.
Shutdown Mode The MAX1672 EV kit features a shutdown mode that preserves battery life by reducing quiescent current to less than 1A max. During shutdown, the reference, low-battery comparator, and all feedback and control circuitry are turned off. In shutdown, the output of the boost converter drops to within a Schottky diode drop below the input, and the linear-regulator output is turned off and pulled to 0V. The 3-pin headers JU3 and JU4 select the shutdown mode. When ONA = 1 or ONB = 0, the MAX1672 is on. When ONA = 0 and ONB = 1, the MAX1672 shuts down. For normal operation, connect ONA to V+ and ONB to GND. Table 3 lists the selectable jumper options.
_______________Detailed Description
The MAX1672 EV kit integrates a step-up switching converter with a linear-regulator output to provide stepup/down voltage conversion. It accepts a 1.8V to 11V input and converts it to a 3.3V or 5V output for currents up to 300mA. The MAX1672 combines a linear regulator, boost switching regulator, N-channel power MOSFET, P-channel pass element, reference, and low-battery comparator in a single, space-saving, 16-pin QSOP package. The EV kit is shipped configured for a 3.3V output.
Table 3. Jumpers JU3 and JU4 Functions
ONA PIN Connected to GND, JU4 = 2 and 3 Connected to GND, JU4 = 2 and 3 Connected to V+, JU4 = 1 and 2 Connected to V+, JU4 = 1 and 2 ONB PIN Connected to GND, JU3 = 2 and 3 Connected to V+, JU3 = 1 and 2 Connected to GND, JU3 = 2 and 3 Connected to V+, JU3 = 1 and 2 MAX1672 OUTPUT MAX1672 enabled, VOUT = 3.3V or 5V Shutdown mode, VOUT = 0V MAX1672 enabled, VOUT = 3.3V or 5V MAX1672 enabled, VOUT = 3.3V or 5V
Jumper Selection
The 3-pin header JU1 selects the output voltage. Table 1 lists the selectable jumper options. The 3-pin header JU2 selects the current limit. Table 2 lists the selectable jumper options. The EV kit is shipped configured for ILIM = 0.8A.
Power-Good Output
The MAX1672 has an on-chip comparator for low-battery detection. If the voltage at the PGI input falls below 1.25V (REF), the open-drain comparator output PGO goes high. The PGI input is connected to an external resistor-divider, R3 and R4, which sets the low-battery detector threshold. Refer to the Low-Battery Detection section of the MAX1672 data sheet for instructions on selecting resistors R3 and R4.
Table 1. Jumper JU1 Functions
SHUNT LOCATION 1&2 2&3 5 3/5 PIN Connected to V+ Connected to GND MAX1672 OUTPUT VOUT = 3.3V VOUT = 5V
Other Output Voltages
Table 2. Jumper JU2 Functions
SHUNT LOCATION 1&2 2&3 ILIM PIN Connected to V+ Connected to GND CURRENT LIMIT ILIM = 0.8A ILIM = 0.5A
The MAX1672 EV kit can also be used to evaluate other output voltages in the 1.25V to 5.5V range. Simply cut the PC trace shorting resistor R2 and refer to the Output Voltage Selection section in the MAX1672 data sheet for instructions on selecting feedback resistors R1 and R2. Place the shunt across pins 2 and 3 of JU1.
2
_______________________________________________________________________________________
MAX1672 Evaluation Kit Evaluates: MAX1672
VIN +1.8V TO +11V R3 OPEN 12 R4 SHORT (PC TRACE) 1 2 3 V+ JU2 1 2 3 13 R5 1M C3 0.1F 7 V+ JU4 ONA 3 GND 14 10 V+ 2 4 ONA 3/5 5 2 1 JU1 3 9 C4 10F 10V PGO FB 8 ILIM PS 11 PGND 15 6 IN PGI LX 1 D1 MBRS130 L1 10H
C1 100F 16V
C5 0.1F
V+
V+
U1
MAX1672
3 ONB
LX PGND
16 2
JU3 ONB
C2 100F 16V
C7 0.1F
REF 1.25V VOUT PWRGD
REF
OUT
VOUT C6 0.1F R1 OPEN
1
R2 SHORT (PC TRACE)
SHUNT LOCATION JU1 1-2 JU1 2-3
3/5 PIN V+ GND
MAX1672 OUTPUT 3.3V 5.0V ADJ. MODE CUT R2. SELECT R1 AND R2
JU1 2-3
GND
Figure 1. MAX1672 EV Kit Schematic
_______________________________________________________________________________________
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MAX1672 Evaluation Kit Evaluates: MAX1672
1.0"
Figure 2. MAX1672 EV Kit Component Placement Guide-- Component Side
1.0"
Figure 3. MAX1672 EV Kit PC Board Layout--Component Side
1.0"
Figure 4. MAX1672 EV Kit PC Board Layout--Solder Side
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 (c) 1997 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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