MAX8655EVKIT [MAXIM]
Low-Profile Components;
| 型号： | MAX8655EVKIT |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Low-Profile Components |
| 文件： | 总14页 (文件大小：791K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-4331; Rev 0; 10/08
MAX8655 Evaluation Kit
Evluates:5/MAX68
General Description
Features
The MAX8655 evaluation kit (EV kit) is a fully assem-
bled and tested surface-mount PCB that contains
a fixed-frequency, pulse-width modulated (PWM) step-
down switching regulator. The MAX8655 EV kit
provides a 1.2V output voltage from a 10.8V to 13.2V
input source and delivers up to 20A output current.
The MAX8655 IC features internal high-side and low-
side power MOSFETs.
♦ 10.8V to 13.2V Input-Voltage Range
♦ 20A Maximum Output Current (Additional Airflow
or Heat Sink May be Required Above 13A of
Output Current)
♦ Adjustable Output from 0.7V to 5.5V
♦ Internal High-Side and Low-Side Power MOSFETs
A reference input is provided for use with a high-
accuracy external reference (REFIN) or for DDR and
tracking applications. The MAX8655 EV kit operates at
600kHz. The MAX8655 IC has a programmable internal
oscillator with frequency range from 200kHz to 1MHz.
The MAX8655 can also be synchronized to an external
clock by connecting the clock signal to FSYNC. A syn-
chronization output (SYNCO) is provided to synchro-
nize a second MAX8655 180° out-of-phase with the first
by connecting SYNCO of the first MAX8655 to FSYNC
of the second.
♦ 200kHz to 1MHz Adjustable Switching Frequency
and SYNC Input
♦ SYNCO Synchronizes 2nd Regulator 180° Out-of-
Phase
♦ Monotonic Startup Provides Safe Starting Into a
Pre-Biased Output
♦ Enable Input and Power-OK Signals
♦ Low-Profile Components
♦ Lead-Free and RoHS Compliant
♦ Fully Assembled and Tested
Ordering Information
PART
TYPE
MAX8655EVKIT+
EV Kit
+Denotes lead-free and RoHS compliant.
Component Lists
MAX8655 Circuit
DESIGNATION QTY
DESCRIPTION
DESIGNATION QTY
DESCRIPTION
0.47µF, 10V X5R ceramic capacitors
(0402)
Murata GRM155R61A474KE15
C1
1
Not installed, ceramic capacitor (1210)
C13, C17
C14
2
1
1
1
1
10µF, 25V X5R ceramic capacitors
(1210)
Murata GRM32DR61E106KA12B
C2, C3, C4
3
1µF 20ꢀ, 10V X5R ceramic
capacitor (0603)
Murata GRM188R61A105KA61
2.2µF 20ꢀ, 10V X5R ceramic
capacitor (0603)
Murata GRM188R61A225KE34
C6
1
1000pF 10ꢀ, 50V ceramic capacitor
(0603)
Murata GRM188R71H102KA01
C15
C6A1, C7A,
C8A
0
1
Not installed, ceramic capacitors
0.022µF, 50V X5R ceramic capacitor
(0402)
Murata GRM155R71H223KA12D
0.22µF, 10V ceramic capacitor (0603)
Murata GRM188R71A224KA01
C16
C7
C8
0.22µF, 25V X7R ceramic capacitor
(0603)
Murata GRM188R71E224KA88D
100pF, 50V X7R ceramic capacitor
(0402)
Murata GRM1555C1H101JZ01
1
4
C18
100µF, 6.3V X5R ceramic capacitors
(1210)
Murata GRM32ER60J107ME20
470pF, 50V ceramic capacitor (0402)
Murata GRM155R71H471KA01
C19
1
0
C9–C12
C20, R1
Not installed, ceramic capacitors (0402)
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
MAX8655 Evaluation Kit
Component Lists (continued)
MAX8655 Circuit
DESIGNATION QTY
DESCRIPTION
SMD Schottky diode
Central Semi CM0SH-3 BK
DESIGNATION QTY
DESCRIPTION
R5, R9, R14
R6
0
1
1
1
1
1
2
1
1
1
1
Not installed, resistors (0402)
D1
1
3
4
357Ω 1ꢀ resistor (0402), lead-free
40.2kΩ 1ꢀ resistor (0402), lead-free
2.87kΩ 1ꢀ resistor (0402), lead-free
4.02kΩ 1ꢀ resistor (0402), lead-free
80.6kΩ 1ꢀ resistor (0402), lead-free
100kΩ 1ꢀ resistors (0402), lead-free
56.2kΩ 1ꢀ resistor (0402), lead-free
41.2kΩ 1ꢀ resistor (0402), lead-free
51.1kΩ 1ꢀ resistor (0402), lead-free
10Ω 1ꢀ resistor (0402), lead-free
Terminal blocks, 5mm
On Shore EDZ500/2DS
Digi-Key ED1975-ND
R7
JP1, JP3, JP9
R8
R10
JP2, JP5, JP6,
JP7
2-pin headers, 0.1in
R11
R12, R35
R13
JP4
1
2
4-pin header, 0.1in
3-pin headers, 0.1in
JP8, JP10
R15
0.56µH, 1.8mΩ, 27.5A inductor
(11.5mm x 10.3mm x 4mm)
Vishay IHLP-4040DZ-ERR56M01
R16
L1
1
R18
R2, R17
R3
2
1
1
0Ω 1ꢀ resistors (0402), lead-free
3.3Ω 1ꢀ resistor (1206), lead-free
681Ω 1ꢀ resistor (0402), lead-free
Synchronous-PWM buck regulator
(56 TQFN-EP*)
Maxim MAX8655ETN+
U1
1
R4
*EP = Exposed pad.
MAX8688 Circuit—Not Installed
DESIGNATION QTY
DESCRIPTION
DESIGNATION QTY
DESCRIPTION
C201, C202,
C203, C205,
C206, C207
100nF 10ꢀ, 50V X7R ceramic
capacitors (0603), open
Murata GRM188R71H104KA93
R201, R204,
R206, R208,
R209, R214
0
0
0
Resistors, open (0402)
1µF 10ꢀ, 10V X5R ceramic
capacitor (0603), open
Murata GRM188R61A105KA61
R202
R203
0
0
0Ω resistor (0603)
C204
1kΩ 1ꢀ resistor (0402), open
Evluates:5/MAX68
R205, R207,
R210
0
33kΩ 1ꢀ resistors (0402), open
2.2µF 10ꢀ, 10V X5R ceramic
capacitor (0603), open
Murata GRM188R61A225KE34
C208
C209
C210
JP201
0
0
0
R211
R212
0
0
0
0
0
300Ω 5ꢀ resistor (0603), open
499Ω 1ꢀ resistor (0603)
Ceramic capacitor, open
R213
100kΩ 1ꢀ resistor (0603), open
10kΩ 1ꢀ resistor (0402), open
100Ω 1ꢀ resistors (0402), open
0.47µF 10ꢀ, 10V X5R ceramic
capacitor (0603), open
Murata GRM188R61A474KA61
R215
R216, R217
Digital power-supply controller, open
Maxim MAX8688+
0
0
0
4-pin header, open
U201
U202
U203
0
0
0
JP202, JP203,
JP204
3-pin headers, open
AT24C01A-10TSU-1.8, open
Voltage regulator (SOT-223)
NS LM317EMP
R19
100kΩ 1ꢀ resistor, open (0402)
Component Suppliers
SUPPLIER
PHONE
WEBSITE
Central Semiconductor
Digi-Key Corp.
631-435-1110
800-344-4539
770-436-1300
402-563-6866
www.centralsemi.com
www.digikey.com
Murata Electronics North America, Inc.
Vishay
www.murata-northamerica.com
www.vishay.com
Note: Indicate that you are using the MAX8655 when contacting these component suppliers.
2
_______________________________________________________________________________________
MAX8655 Evaluation Kit
Evluates:5/MAX68
The EV kit features an FSYNC pad to allow the convert-
er to synchronize with an external clock. See the
Evaluating Other Switching Frequencies and External
Clock Synchronization (FSYNC and SYNCO) section.
Quick Start
Recommended Equipment
Before beginning, the following equipment is needed:
•
•
•
•
•
MAX8655 EV kit
Evaluating Other Output Voltages
The output voltage of the MAX8655 can be adjusted
from 0.7V (min) to 5.5V (max). To set the output voltage
for the MAX8655, connect FB to the center of an exter-
nal resistor-divider from the output to GND (R8 and R10
of the MAX8655 EV kit). Select R10 between 5kΩ and
24kΩ, and then calculate R8 with the following equation:
Up to 12V at 5A adjustable DC power supply
Digital multimeters (DMM)
Up to 20A load
Ammeter (optional)
Procedure
The MAX8655 EV kit is fully assembled and tested.
Follow the steps below to verify board operation.
Caution: Do not turn on the power supply until all
connections are completed.
⎛
⎞
V
V
OUT
R8 = R10 ×
−1
⎟
⎜
⎝
⎠
FB
where V
= 0.7V or V
. Resistors R8 and R10
REFIN
FB
1) Set the power-supply output to 12V. Turn off the
power supply.
should be placed as close as possible to the IC.
Refer to the MAX8655 IC data sheet to calculate other
associated components.
2) Verify that there is a shunt across the pins of jumper
JP2 (SCOMP and GND).
3) Verify that there is a shunt across pins 2-3 of
jumper JP8 (MODE and GND).
Evaluating Other Switching Frequencies
and External Clock Synchronization
(FSYNC and SYNCO)
4) Verify that there is a shunt across jumper JP5 (AVL
and REFIN).
The MAX8655 has an adjustable internal oscillator that
can be set to any frequency from 200kHz to 1MHz. To
set the switching frequency, connect a resistor
5) Connect the positive lead of the power supply to
the VIN pad of the JP1 terminal block and connect
the negative lead of the power supply to the GND
pad of the JP9 terminal on the EV kit.
(R
) from FSYNC to GND. R is calculated as:
FSYNC FSYNC
30600
R
=
− 9.914
6) Connect the positive lead of the DMM to the VOUT
pad and connect the negative lead of the DMM to
the GND pad on the EV kit.
FSYNC
f
s
where f is the desired switching frequency in kilohertz.
S
7) Turn on the power supply.
The MAX8655 can also be synchronized to an external
clock by connecting the clock signal to FSYNC. A syn-
chronization output (SYNCO) generates a clock signal
that is 180° out-of-phase, which allows for another
MAX8655 to be synchronized 180° out-of-phase with
the first, by connecting SYNCO of the first MAX8655 to
FSYNC of the second to reduce the input ripple current.
8) Verify that the output voltage is 1.2V at the out-
put (between JP3 and JP9 terminals) of the
MAX8655_MAX8688 EV board.
9) Connect the load between VOUT and GND.
10) Verify that the voltage at VOUT is approximately
1.2V.
Undervoltage Lockout (UVLO)
Detailed Description of Hardware
When V
drops below 4.03V, the MAX8655 assumes
AVL
The MAX8655 EV kit operates from a 10.8V to 13.2V
input and generates an output voltage of 1.2V at loads
up to 20A.The MAX8655 EV kit features a circuit of a
step-down regulator operating on a PWM, peak cur-
rent-mode control scheme. Integrated power
MOSFETs provide a small footprint, ease of layout, and
reduced EMI.
that the supply voltage is too low to make valid
decisions, so the undervoltage-lockout (UVLO) circuitry
inhibits switching and turns off both internal power
MOSFETs. When V
rises above 4.15V, the reg-
AVL
ulator enters the startup sequence and then resumes
normal operation.
_______________________________________________________________________________________
3
MAX8655 Evaluation Kit
The peak current limit is used to sense the inductor cur-
rent, and is more accurate than the valley current limit
since it does not depend upon the on-resistance of the
low-side MOSFET.
Power-OK (POK)
POK is an open-drain output on the MAX8655 that mon-
itors the output voltage. When the output is above 92ꢀ
of its nominal regulation voltage, POK is high imped-
ance. When the output drops below 89ꢀ of its nominal
regulation voltage, POK is internally pulled low. POK is
also internally pulled low when the MAX8655 is shut
down or in a fault condition.
Valley Current Limit
The MAX8655 has an adjustable valley current limit,
configurable for foldback with automatic recovery, or
constant current limit with latch-up. The valley current is
sensed across the on-resistance of the low-side
MOSFET. When the latch-off mode is used, connect
MODE to AVL and set the current-limit threshold with
one resistor from ILIM2 to GND. To use foldback cur-
rent limit with auto recovery, connect MODE to GND
and connect a resistor from ILIM2 to the output (R11),
and another resistor from ILIM2 to GND (R16). Cycle
EN or input power to reset the current-limit latch. For
further information refer to the Setting the Current Limit
section in the MAX8655 IC data sheet.
Soft-Start and REFIN
The internal soft-start circuitry gradually ramps up the
reference voltage to control the rate of rise of the output
voltage and reduce input surge currents during startup.
The soft-start period is determined by the value of the
capacitor from SS to GND. The soft-start time is approx-
imately given by:
t
=
× C
30.4ms/µF
SS
(
)
SS
Overvoltage Protection (OVP)
The MAX8655 provides output overvoltage protection
(OVP), which is set independent of the output regula-
tion voltage with a resistor voltage-divider connected
between the output and GND (R9 and R14 of
Figure 1a). When the voltage at OVP exceeds the OVP
threshold, the regulator stops switching and latches on
the low-side power MOSFET. Cycle EN or the power
applied to AVL to clear the latch.
where t = soft-start time in seconds and C is the
SS
SS
value of the capacitor at the SS pin.
The MAX8655 also features monotonic output-voltage
rise, which allows the MAX8655 to safely start up into a
prebiased output without pulling the output voltage down.
The MAX8655 has a reference input (REFIN). When an
external reference up to 1.5V is connected to REFIN,
the feedback regulation voltage is equal to the voltage
applied to REFIN.
Select R14 between 5kΩ and 24kΩ, then calculate R9
with the following equation:
Evluates:5/MAX68
Connect REFIN to AVL to use the internal 0.7V refer-
ence (jumper JP5).
⎛
⎞
V
V
OUT
R9 = R14 ×
−1
⎜
⎟
Current Limit
The MAX8655 uses both foldback and peak current
limiting.
⎝
⎠
OVP
where V
= 1.15 x V and V = voltage at which
OUT
OVP
FB
OVP protection should set in.
Peak Current Limit
The peak current-limit threshold (V ) is set by a resis-
TH
Evaluating the MAX8688
The MAX8688 is a fully digital power-supply manager
that can be tested in conjunction with the MAX8655.
Samples of the MAX8688 IC can be ordered from
Maxim. To test the MAX8688, populate it with its circuit-
ry, as shown in the schematic or in the component list.
Populate R215 with 10kΩ to connect pin 3 of JP201
(RST) and pin 1 of JP204 (3.3V). Also, remove the shunt
on pins 1-2 of JP5. For further information, refer to the
MAX8688 IC data sheet.
tor connected from ILIM1 to GND (R
sponds to the peak voltage across the sensing element
(inductor or current-sense resistor). R
as follows:
). V
corre-
ILIM1
TH
is calculated
ILIM1
7.5 × V
10µA
TH
R
=
ILIM1
4
_______________________________________________________________________________________
MAX8655 Evaluation Kit
Evluates:5/MAX68
___________________________________________Typical Operating Characteristic
EFFICIENCY vs. OUTPUT CURRENT
100
90
80
70
60
50
40
30
20
10
0
0
2
4
6
8
10 12 14 16 18 20
OUTPUT CURRENT (A)
_______________________________________________________________________________________
5
MAX8655 Evaluation Kit
P V I N
P V I N
P V I N
P V I N
P V I N
P V I N
P V I N
P V I N
P V I N
P V I N
P V I N
F S Y N C
S Y N C O
O V P
M O D E
E N
Evluates:5/MAX68
P O K
Figure 1a. MAX8655 EV Kit Schematic (Sheet 1 of 2)
6
_______________________________________________________________________________________
MAX8655 Evaluation Kit
Evluates:5/MAX68
A D J
1
Figure 1b. MAX8655 EV Kit Schematic (Sheet 2 of 2)
_______________________________________________________________________________________
7
MAX8655 Evaluation Kit
Evluates:5/MAX68
Figure 2. MAX8655 EV Kit Component Placement Guide—Component Side
8
_______________________________________________________________________________________
MAX8655 Evaluation Kit
Evluates:5/MAX68
Figure 3. MAX8655 EV Kit PCB Layout—Component Side
_______________________________________________________________________________________
9
MAX8655 Evaluation Kit
Evluates:5/MAX68
Figure 4. MAX8655 EV Kit PCB Layout—Inner Layer 1
10 ______________________________________________________________________________________
MAX8655 Evaluation Kit
Evluates:5/MAX68
Figure 5. MAX8655 EV Kit PCB Layout—Inner Layer 2
______________________________________________________________________________________ 11
MAX8655 Evaluation Kit
Evluates:5/MAX68
Figure 6. MAX8655 EV Kit PCB Layout—Inner Layer 3
12 ______________________________________________________________________________________
MAX8655 Evaluation Kit
Evluates:5/MAX68
Figure 7. MAX8655 EV Kit PCB Layout—Inner Layer 4
______________________________________________________________________________________ 13
MAX8655 Evaluation Kit
Evluates:5/MAX68
Figure 8. MAX8655 EV Kit PCB 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.
14 __________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2008 Maxim Integrated Products
is a registered trademark of Maxim Integrated Products, Inc.
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