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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 out-
put current.
The board includes clips for a standard AA-size bat-
tery, 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!
V
IN
(V)
1.2
2.4
2.4
3.6
V
OUT
(V)
3.3
3.3
5.0
5.0
I
OUT
(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
0.22µF ceramic capacitor
0.1µF ceramic capacitors
4.7nF ceramic capacitors
100µF, 6V, 0.1ESR capacitors
AVX TPSD107M010R0100
Open
22µF, 6V, low-ESR capacitor
AVX TPSD226M025R0200
Open
0.5A, 20V Schottky diode
Motorola MBR0520L
10-pin header
2-pin header
3-pin header
10µH, 1.65A, 4.5mm inductor
Sumida CDR74B-100
10Ω, 5% resistor
61.9kΩ, 1% resistor
Open
Battery clips Keystone 92
1kΩ, 5% resistors
6.81kΩ, 1% resistor
1MΩ, 5% resistors
100kΩ, 5% resistor
Maxim MAX849ESE
______________Ordering Information
PART
MAX849EVKIT-SO
TEMP. RANGE
0°C to +70°C
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 com-
pleted.
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 10µF, and replace L1 with a
22µH, 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 V
OUT
.
PWM synchronized to user-
supplied 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 (µC'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 µC must sense the pulse frequen-
cy so it can sample DOUT for the correct period of
time. Use the LX output to measure the MAX849’s inter-
nal frequency.
If the MAX849 is operated in synchronized PWM mode
(JU2 = open and CLK/SEL driven externally), then the
µC 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
10µF, 6V, low-ESR capacitor
AVX TPSD106M035R0300
(10µF, 35V, 0.300Ω max ESR)
22µH, 800mA inductor
Sumida CD54-220
(22µH, 1.11A, 0.18Ω)
MAX848ESE
FUNCTION
L1
U1
1
1
Setting VOUT and POK Thresholds
When V
OUT
is in regulation, FB = 1.25V, and when
V
OUT
falls to its trip threshold, POKIN drops to 1.25V.
Select R3, R5, and R2 by the following method:
V
OUT
= Nominal output voltage
V
TRIP
= Desired POK trip threshold
I
BIAS
= Desired resistor bias current, at least 10µA
V
REF
= 1.25V
R2 = V
REF
/ I
BIAS
R5 = R2 (V
OUT
- VT
RIP
) / V
TRIP
R3 = (R2 + R5) [(V
TRIP
/ V
REF
) - 1]
To set V
OUT
= 5.0V, set R3 to 178kΩ (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
0.22µF
CC1210
AIN2
1
2
3
4
5
C2
POK
6
7
0.1µF
CC1206
R3
OPEN
R1
10Ω
8
LX
D1
MOTOROLA
MBR0520L
L1
SUMIDA
CDR74B-100
10µH, 1.65A
C3
0.1µF
CC1210
CF1, CF2, CF3
100µF
10V
EXTCLK
DATA
AINSEL
VOUT
VOUT
JU2
JUMPER2
1
2
3
POKIN
VOUT
AGND
AGND
ON1
ON2
EXTCLK
AINSEL
CI1, CI2
22µF
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
6.81kΩ, 1%
JU1
R2
61.9kΩ, 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 µP 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
© 1996 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.

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