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19-1749; Rev 0; 10/96
MAX849 Evaluation Kit
_______________General Description
The MAX849 evaluation kit (EV kit) is an assembled and tested PC board that implements a complete, one-cell to three-cell, high-power, low-noise, step-up DC-DC power converter that's ideal for portable phones and other battery-operated equipment. With a 3.3V output voltage, use one or two cells to get a 250mA to 700mA output current. With a 5V output voltage, use three cells or one lithium-ion (Li-Ion) battery to get an 850mA output current. The board includes clips for a standard AA-size battery, and provides a 10-pin header for user interfacing. To evaluate the MAX848, order a free sample of the MAX848ESE along with the MAX849 EV kit.
____________________________Features
o 250mA to 850mA Output Current!
VIN (V) 1.2 2.4 2.4 3.6 VOUT (V) 3.3 3.3 5.0 5.0 IOUT (mA) 250 700 500 850
Evaluates: MAX848/MAX849
o 90% Efficiency o Proven PC Board Layout o Fully Assembled and Tested o 2-Channel Analog-to-Digital Converter (ADC) with Serial Output for Voltage Monitoring
____________________Component List
DESIGNATION QTY BAT1 C1 C2, C3 C4, C5 CF1, CF2 CF3 CI1 CI2 D1 J1 JU1 JU2 L1 R1 R2 R3 R4, R11 R5 R6, R7, R9, R10 R8 U1 2 1 2 2 2 0 1 0 1 1 1 1 1 1 1 0 2 2 1 4 1 1 DESCRIPTION Battery clips Keystone 92 0.22F ceramic capacitor 0.1F ceramic capacitors 4.7nF ceramic capacitors 100F, 6V, 0.1ESR capacitors AVX TPSD107M010R0100 Open 22F, 6V, low-ESR capacitor AVX TPSD226M025R0200 Open 0.5A, 20V Schottky diode Motorola MBR0520L 10-pin header 2-pin header 3-pin header 10H, 1.65A, 4.5mm inductor Sumida CDR74B-100 10, 5% resistor 61.9k, 1% resistor Open Battery clips Keystone 92 1k, 5% resistors 6.81k, 1% resistor 1M, 5% resistors 100k, 5% resistor Maxim MAX849ESE
______________Ordering Information
PART MAX849EVKIT-SO TEMP. RANGE 0C to +70C BOARD TYPE Surface Mount
_____________________________________Quick
Start
This section describes how to operate the MAX849 EV kit, and how to evaluate its performance. Do not turn on the power supply until all connections are completed. 1) Configure the jumper and resistor settings as desired. For a standard 3.3V output and 90% power-OK threshold, close jumper JU1 (Table 1). 2) Insert an AA-size battery cell into the battery clips. Or, connect a 1V to 3V DC power supply to the VIN and GND input pads. Turn on the power supply. Quiescent supply current for the board with no load should be less than 1mA. 3) The EV kit board turns on automatically, and VOUT goes to 3.3V. 4) To operate in high-power PWM mode at a particular frequency between 200kHz and 400kHz, leave JU2 open and drive the CLK/SEL pin with pulses at the desired frequency. Or, let the MAX849 determine its own PWM frequency by connecting JU2 1-2. To operate in low-power PFM mode, connect JU2 2-3.
________________________________________________________________ Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
MAX849 Evaluation Kit Evaluates: MAX848/MAX849
_______________Detailed Description
Evaluating the MAX848
To evaluate the MAX848, first replace U1 with a MAX848ESE. Then remove filter capacitor CF2, replace input capacitor CI1 with 10F, and replace L1 with a 22H, 800mA inductor. Table 2 lists recommended component changes for MAX848 evaluation.
Table 1. Jumper Function Table
JUMPER STATE Open JU1 Closed (default) 1-2 JU2 Open 2-3 (default R9) 3.3V, 10% trip threshold Low-noise PWM mode. CLK/SEL pin is tied to VOUT. PWM synchronized to usersupplied CLK/SEL signal. Low-power PFM mode. CLK/SEL pin is tied to GND. FUNCTION VOUT and POK set by R3, R5, and R2.
Reading the Analog-to-Digital Converter (ADC)
The MAX849's internal ADC produces a pulse train on the DOUT pin, at the CLK/SEL switching frequency. Pulses are skipped in proportion to the selected analog input. One way to read a value from the ADC is to use a microcontroller's (C's) pulse accumulator or counter/ timer. With the MAX849's DOUT incrementing the counter, clear it and latch its value after 256 CLK/SEL pulses. The counter's value will be proportional to the analog input voltage. If the MAX849 is operated in free-running PWM mode (JU2 = 1-2), then the C must sense the pulse frequency so it can sample DOUT for the correct period of time. Use the LX output to measure the MAX849's internal frequency. If the MAX849 is operated in synchronized PWM mode (JU2 = open and CLK/SEL driven externally), then the C should use the CLK/SEL pulses to time the DOUT sampling period. The ADC is not active when CLK/SEL is driven low (JU2 = 2-3).
Table 2. Recommended Component Changes for MAX848 Evaluation
DESIGNATION CF2 CI1 QTY 0 1 Open 10F, 6V, low-ESR capacitor AVX TPSD106M035R0300 (10F, 35V, 0.300 max ESR) 22H, 800mA inductor Sumida CD54-220 (22H, 1.11A, 0.18) MAX848ESE FUNCTION
L1 U1
1 1
Setting VOUT and POK Thresholds
When V OUT is in regulation, FB = 1.25V, and when VOUT falls to its trip threshold, POKIN drops to 1.25V. Select R3, R5, and R2 by the following method: VOUT = Nominal output voltage VTRIP = Desired POK trip threshold IBIAS = Desired resistor bias current, at least 10A VREF = 1.25V R2 = VREF / IBIAS R5 = R2 (VOUT - VTRIP) / VTRIP R3 = (R2 + R5) [(VTRIP / VREF) - 1] To set VOUT = 5.0V, set R3 to 178k (do not connect or disconnect JU1 or R3 while the power is on).
2
_______________________________________________________________________________________
MAX849 Evaluation Kit Evaluates: MAX848/MAX849
VOUT1 ON2 ON1 C1 AIN1 0.22F CC1210 AIN2 1 2 3 4 5 C2 POK 6 7 0.1F CC1206 R3 OPEN R1 10 8 LX D1 MOTOROLA MBR0520L L1 SUMIDA CDR74B-100 10H, 1.65A C3 0.1F CC1210 CF1, CF2, CF3 100F 10V EXTCLK DATA AINSEL VOUT VOUT JU2 JUMPER2 1 2 3 POKIN VOUT AGND AGND ON1 ON2 EXTCLK AINSEL CI1, CI2 22F 6V BAT1 PGND GND1
U1
AIN1 MAX849 ON1 AIN2 REF GND OUT POKIN FB POK ON2 POUT LX PGND CLK/SEL DATA AINSEL 16 15 14 13 12 11 10 9 LX
VIN
VIN1
R5 6.81k, 1%
JU1
R2 61.9k, 1%
R8 100k
FB = AGND FOR 3.3V OUTPUT POKIN = AGND FOR DEFAULT 10% TRIP THRESHOLD
1M R6
1M R7
1M R9
1M R10
OPTIONAL P INTERFACE 10-PIN HEADER
VOUT J4-1 J4-2 J4-3 J4-2 EXTCLK DATA J4-5 J4-6 J4-7 J4-8 J4-9 J4-10 AGND AINSEL POK AGND1 ON1 ON2 LX AIN2 AIN1
R4, 1k CC1206
AGND
AIN1 C4 4.7nF CC1206
R4, 1k CC1206
AGND
AIN2 C5 4.7nF CC1206
AGND
Figure 1. MAX849 EV Kit Schematic
_______________________________________________________________________________________ 3
MAX849 Evaluation Kit Evaluates: MAX848/MAX849
Figure 2. MAX849 EV Kit Component Placement Guide
Figure 3. MAX849 EV Kit PC Board Layout--Component Side
Figure 4. MAX849 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) 1996 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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