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19-1962; Rev 1; 7/01
MAX1774 Evaluation Kit
General Description
The MAX1774 evaluation kit (EV kit) is a fully assembled and tested surface-mount circuit board that contains a dual step-down switching converter with a backup converter circuit and low-voltage detectors. The circuit is configured for a main output voltage of 3.3V and a core output voltage of 1.8V. The main output provides up to 1.5A, and the core output provides up to 500mA of current. Power for the circuit can be provided from a 3.65V to 5.5V DC source. The EV kit can be reconfigured for input voltages up to 28V. The core's input can be powered from the input source, or for higher input voltages, from the main output. The EV kit circuit includes battery monitoring, switchover, and backup, allowing automatic backup operation. The MAX1774 EV kit demonstrates low quiescent current and high efficiency (up to 95%) for maximum battery life. Operation up to 1.25MHz allows the use of tiny surfacemount components.
Features
o Input Voltages +3.65V to +5.5V (AC Adapter, as configured) +2.7V to +5.5V (Main Battery, as configured) +0.9V to +3.2V (Backup Battery) o Output Voltages +3.3V Output at 1.5A +1.8V Output at 500mA o Outputs are Adjustable with Resistors o Internal MOSFET Switches (Core and Backup Converters) o 8A (typ) IC Shutdown Current o Switching Frequency up to 1.25MHz o Surface-Mount Components o Fully Assembled and Tested
Evaluates: MAX1774
Component List
DESIGNATION C1, C11, C14 C2, C8 QTY 0 2 DESCRIPTION Not installed (0805) 10F, 25V X5R ceramic capacitors (1812) Taiyo Yuden TMK432BJ106KM 47F, 6.3V low-ESR electrolytic capacitor (POSCAP) Sanyo 6TPA47M 47F, 6.3V tantalum capacitor (C) AVX TPSC476M016R0350 or Sprague-Vishay 592D476X06R3C2T 10F, 6.3V X5R ceramic capacitors (1206) 1F, 25V X7R ceramic capacitors (1206) 0.22F, 25V X7R ceramic capacitor (1206) Taiyo Yuden TMK316BJ224KF 100pF, 50V, NPO ceramic capacitor (0805) 3A, 100V diode Nihon NSD03A10 0.5A, 30V Schottky diode Nihon EP05Q03L MAX1774EVKIT PART
Ordering Information
TEMP. RANGE 0C to +70C IC PACKAGE 32-Pin 7mm 7mm QFN
Component Suppliers
SUPPLIER AVX Central Semiconductor Dale-Vishay Fairchild Nihon USA Sanyo USA Sprague-Vishay Sumida Taiyo Yuden PHONE 803-996-0690 516-435-1110 402-564-3131 408-822-2000 661-867-2555 619-661-6835 603-224-1961 847-956-0666 408-573-4150 FAX 803-626-3123 516-435-1824 402-563-6418 408-822-2102 661-867-2698 619-661-1055 603-224-1430 847-956-0702 408-573-4159
C3
1
C4
1
C5, C10, C13 C6, C7
3 2
C9
1
Note: Please indicate that you are using the MAX1774 when contacting these component suppliers.
C12 D1 D2
1 1 1
Component List continues on next page. ________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
MAX1774 Evaluation Kit Evaluates: MAX1774
Component List (continued)
DESIGNATION QTY DESCRIPTION Not installed, (SOT-23) recommended Central Semiconductor CMPD914 Not installed, (SOD-323) recommended Central Semiconductor CMDZ5248B 5.0H, 2.4A inductor Sumida CDRH6D28-5R0NC 5.4H, 1.6A inductor Sumida CDRH5D18-5R4NC 22H, 700mA inductor Sumida CDRH4D28-220 +30V/-20V, 5.5A/4.0A N/Pchannel MOSFET (SO-8) Fairchild Semiconductor FDS8928A -30V, 1.1A P-channel MOSFET (SuperSOT-3) Fairchild Semiconductor NDS356AP DESIGNATION R1 R2 R3 R8 R9 R10 R11, R13, R14 R15, R19 R17 R18 R4, R5, R12, R16 U1 JU1, JU2 None None None None QTY 1 1 1 1 1 1 5 1 1 0 1 2 2 1 1 1 DESCRIPTION 24.3k 1% resistor (0805) 30.1k 1% resistor (0805) 0.033, 0.5W 1% resistor (2010) Dale WSL-2010-R033 255k 1% resistor (0805) 22.6k 1% resistor (0805) 200k 1% resistor (0805) 1M 5% resistors (0805) 66.5k 1% resistor (0805) 40.2k 1% resistor (0805) Not installed (0805) MAX1774EGJ (32-pin 7mm 7mm QFN) 3-pin headers Shunts (JU1, JU2) MAX1774 PC board MAX1774 data sheet MAX1774 EV kit data sheet
D3
0
D4
0
L1 L2 L3
1 1 1
P1A/P1B
1
P2
1
Quick Start
The MAX1774 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 shunts are across pins 1 and 2 of jumpers JU1 (SHDNM) and JU2 (SHDNC). 2) Connect a voltmeter to the VMAIN pad. 3) Connect a +3.65V to +5.5V DC power supply to the VIN_AC pad. Connect the supply ground to the GND pad. 4) Connect a +3.4V to +5.5V DC power supply to the MAIN_BATT pad. Connect the supply ground to the GND pad. Set this power supply +1V below the power-supply voltage connected to the VIN_AC pad. 5) Turn on the VIN_AC power supply, and then the MAIN_BATT power supply. 6) Verify that the main output (VMAIN) is +3.3V and the core output (VCORE) is +1.8V.
7) Turn off the VIN_AC power supply, and verify that the main output (VMAIN) is +3.3V and the core output (VCORE) is +1.8V. For instructions on selecting the feedback resistors for other output voltages, see Evaluating Other Output Voltages.
Detailed Description
The MAX1774 EV kit contains a dual step-down switching converter and backup converter. A +3.3V main output provides up to 1.5A, and a +1.8V core output provides up to 500mA of current. The EV kit operates from a +2.7V to +5.5V input voltage range. See Evaluating High-Input-Voltage Operation to reconfigure the EV kit for input voltages up to +28V. A backup step-up converter is designed into the circuit and only requires three components to be fully operational, supplying up to 20mA of current to the main output (VMAIN). When the backup converter is engaged, it regulates to the same voltage as VMAIN, and serves to backup the output (at a reduced load) during a deadbattery condition.
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MAX1774 Evaluation Kit
The MAX1774 EV kit features several jumper-selectable options. Shutdown mode jumpers that reduce the MAX1774 shutdown current to less than 8A (typ) are provided for the main and core outputs. Power to the core input can be fed from the main output (VMAIN) or an external voltage source. The available main output load current will be reduced by the amount of current drawn by the core converter (VCORE). Note that if the power to the core output comes from the main output, the core output will not be able to supply power when the main is disabled. Low-voltage detector pads are provided on the EV kit for low AC-adapter voltage (ACO), low-battery output (LBO), and backup (BKUP) features. The main step-down switching-converter output-voltage can be adjusted from +1.25V to +5.5V, and the core output voltage can be adjusted from +1V to +5V with resistors.
Evaluates: MAX1774
Table 1. Jumper JU1 Function
SHUNT LOCATION 1 and 2 2 and 3 SHDNM PIN Connected to IN Connected to GND MAX1774 OUTPUT MAX1774 enabled, VMAIN = +3.3V Shutdown mode, VMAIN = 0V
Table 2. Jumper JU2 Function
SHUNT LOCATION 1 and 2 2 and 3 SHDNC PIN Connected to CVL Connected to GND MAX1774 OUTPUT CORE output enabled, VCORE = +1.8V Shutdown mode, VCORE = 0V
Jumper Selection
Shutdown Mode (Main Output) The MAX1774 EV kit features a shutdown mode that reduces the MAX1774 shutdown current to less than 8A (typ), preserving battery life. The 3-pin jumper (JU1) selects the MAX1774 shutdown mode. Table 1 lists the selectable jumper options. Shutdown Mode (Core Output) The MAX1774 EV kit features a core shutdown mode that reduces the MAX1774 shutdown current, thus preserving battery life. The 3-pin jumper (JU2) selects the shutdown mode for the MAX1774 core output. Table 2 lists the selectable jumper options. Core Input Supply The MAX1774 EV kit features an option to allow the main output to power the core's input. Jumper JU3 selects which voltage source feeds the core's input. Table 3 lists the jumper options.
Table 3. Jumper JU3 Functions
PIN-HOLE TRACE 1 and 2 (PC trace shorts 1 and 2) Shorts 2 and 3 (Cut open trace across pin-holes 1 and 2 ) INC PIN Connected to IN OPERATING MODE IN voltage source feeds core input VMAIN voltage source feeds core input
Connected to VMAIN (core cascaded)
Evaluating Other Output Voltages
MAIN Output The MAX1774 EV kit's step-down switching converter main output (VMAIN) is set to +3.3V by feedback resistors (R17, R18). To generate output voltages other than +3.3V (+1.25V to +5.5V), select different voltage-divider resistors (R17, R18). Refer to the Setting the Output Voltages in the MAX1774 data sheet for instructions on selecting the resistors.
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MAX1774 Evaluation Kit Evaluates: MAX1774
CORE Output The MAX1774 EV kit's step-down switching converter core output (VCORE) is set to +1.8V by feedback resistors (R1, R2). To generate output voltages other than +1.8V (+1V to +5V), select different voltage-divider resistors (R1, R2). Refer to the Setting the Output Voltages in the MAX1774 data sheet for instructions on selecting the resistors. tion, IN voltage is limited to 28V and the main output voltage may be set between +2.6V and +5.5V.
Evaluating The Backup Converter
Backup Converter Circuit The MAX1774 EV kit features a backup converter utilizing a step-up converter to provide power (up to 20mA) to the main output (VMAIN) when the main battery (MAIN_BATT) is off and no AC (VIN_AC) is connected. Using A Rechargeable Backup Battery The MAX1774 EV kit features a circuit to recharge the backup battery. To use this function, install D3 and resistor R12. Follow the battery manufacturer's guidelines for safely recharging the backup battery. To prevent overdischarge of the backup battery, install resistors R4 and R5. The battery discharge threshold voltage is 0.5V(1 + (R4 / R5)), with R5 being 100k. When the circuit is in backup mode and the backup battery discharges below the threshold, the circuit will shut down.
Evaluating High-Input-Voltage Operation
Core Input The MAX1774 EV kit is factory set so that both stepdown switching regulators derive their power from the input voltage (IN). Since the input to the core regulator is limited to +5.5V, a cascaded configuration must be used for input voltages greater than +5.5V (the core converter derives its power from the main output voltage). To configure the MAX1774 EV kit cascaded, cut open the PC board trace shorting pin-holes 1 and 2 at jumper JU3. Place a short (soldered jumper wire) across pin-holes 2 and 3 at jumper JU3. Consult Table 3 for input-voltage jumper selection. In this configura-
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IN VIN_AC +3.65V TO +5.5V AC ADAPTER IN D1 C6 1F 6 IN 3 7 P1-B CS+ +3.3V VMAIN GND 5 MDRV 7 NDRV 14 DBI PGND 5 1 R9 22.6k 1% 15 LBI INS 27 19 CS+ 20 CS23 INC 4 P1-A 2 R3 33m 1% 8 C3 47F 6.3V 6 L1 5H 4 C10 10F 6.3V C2 10F GND CVH P2 3 1 R8 255k 1% 1 R16 SHORT R11 1M D4 OPEN 2 PDRV 8
+2.7V TO +5.5V MAIN_BATT
C1 OPEN
Figure 1. MAX1774 EV Kit Schematic
IN JU3 3 SHORT 2 (PC TRACE) 1 R10 200k 1%
GND
U1
C13 10F 6.3V
IN
VIN_AC D3 OPEN C8 10F D2 9 LXB CVL C7 1F 5 10 LXB2 12 BKOFF ACO 16 REF LBO BKUP 32 VIN SHDNM 18 R18 40.2k C11 OPEN 3 FBM SHDNC C14 OPEN 31 JU2 21 CVL 30 JU1 1 2 3 SHDNM 26 C9 0.22F 22 GND 2 PGNDC 24 C5 10F 6.3V R4 SHORT R5 OPEN CVL R2 30.1k 1% R12 OPEN L3 22H L2 5.4H
R19 1M 5%
13 MAX1774 LXC 28 ACI 11 BIN 21 FBC
R1 24.3k 1% C12 100pF R13 1M
C4 47F 6.3V
+1.8V VCORE GND
VMAIN R14 1M R15 1M ACO LBO BKUP
BKUP_BATT +0.9V TO +3.2V
GND
CS+ 1 JU4 2 3
R17 66.5k
VMAIN
NOTE: PINS 17, 25, 29 ARE NOT CONNECTED. SHDNC
Evaluates: MAX1774
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MAX1774 Evaluation Kit
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MAX1774 Evaluation Kit Evaluates: MAX1774
Figure 2. MAX1774 EV Kit Component Placement Guide-- Component Side
Figure 3. MAX1774 EV Kit PC Board Layout--Component Side
1.0"
Figure 4. MAX1774 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.
6 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2001 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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