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19-0241; Rev 0; 3/94
MAX761 Evaluation Kit
_______________General Description
The MAX761 evaluation kit (EV kit) provides a 12V output for programming flash memories and powering other circuitry. From 5V inputs, it provides better than 85% efficiency for 4mA to 200mA loads. Quiescent supply current is only 300A from a 5V input, and drops to 1A in logic-controlled shutdown. The MAX761 comes in an 8-pin SO package and uses tiny external components; the entire circuit fits into less than 0.3in2.
____________________________Features
o 2V to 12V Input Range for 12V Output o 85% Efficiency for 4mA to 200mA Loads o 1A Shutdown Supply Current o Small External Components o Low-Battery Detector o Current-Limited PFM Control Scheme o Fully Assembled and Tested
MAX761 EV Kit
____________________Component List
DESIGNATION QTY U1 C1, C2 C3, C5 L1 1 2 2 1 DESCRIPTION MAX761CSA 22F, 16V, low-ESR tantalum capacitor Sprague 595D226X0016C2B 0.1F ceramic capacitor 18H, 0.8A inductor (SMT) Sumida CD43-180 1N5817 Schottky diode (SMT) Nihon EC10QS02L Motorola MBRS120LT3 Resistors (not supplied) Capacitor (not supplied) 3-pin header Shunt MAX761 data sheet
______________Ordering Information
PART MAX761EVKIT-SO TEMP. RANGE 0C to +70C PIN-PACKAGE Surface Mount
D1 R1, R2, R3, R4, R5, R6 C4 JU3 None None
1
______________________________EV Kit
0 0 1 1 1
______________Component Suppliers
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________________________________________________________________ Maxim Integrated Products
Call toll free 1-800-998-8800 for free samples or literature.
MAX761 Evaluation Kit MAX761 EV Kit
__________________________________________Typical Operating Characteristics
(MAX761 EV kit, TA = +25C, unless otherwise noted.)
MAXIMUM OUTPUT CURRENT vs. INPUT VOLTAGE
400 MAXIMUM OUTPUT CURRENT (mA) 350 300 BOOTSTRAPPED 250 200 150 100 50 0 0 1 2 3 4 5 6 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 INPUT VOLTAGE (V) INPUT VOLTAGE (V)
EFFICIENCY vs. OUTPUT CURRENT
100 90 80 EFFICIENCY (%) 70 60 50 40 30 20 10 0 0.1 1 10 100 1000 OUTPUT CURRENT (mA) VIN = 2V BOOTSTRAPPED VOUT = 12V VIN = 5V VIN = 3V QUIESCENT CURRENT (mA)
QUIESCENT CURRENT vs. INPUT VOLTAGE
2.00 1.75 1.50 1.25 1.00 0.75 0.50 0.25 0 BOOTSTRAPPED (INTERNAL RESISTORS) VOUT = 12V
SHDN RESPONSE TIME
_________________________Quick Start
12V A
5V 4V B 0V
1ms/div ILOAD = 100mA, VIN = 5V A: VOUT, 2V/div B: SHDN, 2V/div (0V to 4V)
The MAX761 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 5V power supply to the pad marked VIN. Connect ground to the GND pad. 2) Connect a voltmeter and load (if any) to the VOUT pad. 3) For normal operation, place the shunt across pins 1 and 2 on the JU3 jumper. 4) Turn on the power supply and verify that the output voltage is 12V. 5) Instructions for modifying the board for different output voltages are in the Output Voltage Adjustment section.
_______________Detailed Description
Bootstrapped Mode
The MAX761 EV kit is configured for bootstrapped mode. In bootstrapped mode, the MAX761 is powered from the output voltage, which increases efficiency at lower input voltages and requires fewer components. Refer to the Bootstrapped/Non-Bootstrapped Mode section of the MAX761 data sheet for further details. For an adjustable output in bootstrapped mode, refer to the Output Voltage Adjustment section.
2
_______________________________________________________________________________________
MAX761 Evaluation Kit
Shutdown Control
The MAX761 provides a SHDN pin to disable the output. Table 1 lists the options available for the shutdown control jumper, JU3. To use an external control signal, remove the shunt on JU3 completely and connect the external signal to the pad labeled SHDN. SHDN is a TTL/CMOS-logic-level input. LBI voltage falls below VREF. Resistors R3 and R4 form a voltage divider between the LBI pad and the MAX761 LBI pin. Refer to the Low-Battery Detector section of the MAX761 data sheet for instructions on selecting values for R3 and R4. Note that the printed circuit board trace across R3 shorts the LBI pin to ground when this function is not used. Cut this trace before installing R3. Install a 100k pull-up resistor between VIN (R5) or VOUT (R6) if LBO is used. LBO is disabled in shutdown mode.
MAX761 EV Kit
Table 1. Jumper JU3 Functions
SHUNT LOCATION 1&2 2&3 SHDN PIN Connected to GND Connected to VIN MAX761 OUTPUT MAX761 Enabled VOUT = 12V Shutdown Mode VOUT = VIN - 0.3V
Output Voltage Adjustment
To adjust the output voltage, add output voltage divider resistors R1 and R2 to either bootstrapped or non-bootstrapped configurations. Refer to the Setting the Output Voltage section of the MAX761 data sheet for instructions on selecting values for R1 and R2. When using output voltage divider resistors, disconnect the MAX761 feedback pin (FB) from ground by cutting the thin PC board trace between the pads of JU1. Some users may want to install a small (100pF to 200pF) capacitor (C4), to increase light-load efficiency.
Low-Battery Indicator
The MAX761 provides a low-battery comparator that compares the voltage on LBI to the 1.5V reference voltage. LBO, an open-drain output, goes low when the
1 R6 OPEN R5 OPEN
JU3 23 C1 22F L1 16V 18H 7 8 V+ 3 LBI FB 6 REF GND D1 1N5817
VIN 2V to 12V V+ VOUT 12V
SHDN
4 1
SHDN U1
LX
LB0 R4 OPEN LB1 R3 0 (SHORT)
LBO 2
MAX761
JU2 R2 OPEN C4 OPEN C2 22F 16V
5 C3 0.1F
C5 0.1F JU1
R1 OPEN
Figure 1. MAX761 EV Kit Schematic Diagram
_______________________________________________________________________________________ 3
MAX761 Evaluation Kit MAX761 EV Kit
Figure 2. MAX761 EV Kit Component Placement Guide-- Component Side
Figure 3. MAX761 EV Kit Component Placement Guide-- Solder Side
Figure 4. MAX761 EV Kit PC Board Layout--Component Side
Figure 5. MAX761 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) 1994 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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