MAX8855EVKIT+ [MAXIM]
Fully Protected Against Overcurrent, Short Circuit, and Overtemperature;型号: | MAX8855EVKIT+ |
厂家: | MAXIM INTEGRATED PRODUCTS |
描述: | Fully Protected Against Overcurrent, Short Circuit, and Overtemperature |
文件: | 总11页 (文件大小:258K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
19-5582; Rev 0; 10/10
MAX8855 Evaluation Kit
Evluates:MAX85
General Description
Features
♦ 2.35V to 3.6V Input Supply Voltage Range
♦ 1.8V at 5A Output (Step-Down Regulator 1)
♦ 1.2V at 5A Output (Step-Down Regulator 2)
The MAX8855 evaluation kit (EV kit) is a fully assembled
and tested circuit board that contains all the compo-
nents necessary to evaluate the performance of the
MAX8855. The device is a high-efficiency dual step-
down regulator. The EV kit is powered from a 2.35V to
3.6V DC supply.
♦ 180° Out-of-Phase Operation Reduces Input
Ripple Current
The EV kit is capable of delivering 1.8V at 5A from out-
put 1 and 1.2V at 5A from output 2. The device switch-
ing frequency is set to 1MHz and the two outputs
switch 180° out-of-phase. High-efficiency, internal dual
nMOS design keeps the board cool under heavy loads.
The voltage-mode control architecture and the high-
bandwidth (> 15MHz typ) voltage-error amplifier allow a
type III compensation scheme to be utilized to achieve
fast response under both line and load transients, and
also allow for ceramic output capacitors.
♦ All-Ceramic-Capacitor Design
♦ High Efficiency
♦ 27mΩ On-Resistance Internal MOSFETs
♦ Fully Protected Against Overcurrent, Short
Circuit, and Overtemperature
♦ REFIN on One Channel for Tracking or External
Reference
Programmable soft-start reduces input inrush current.
Two enable inputs allow the turning on/off of each output
individually, resulting in great flexibility for system-level
designs. A reference input facilitates output-voltage
tracking applications.
♦ Integrated Boost Diodes
♦ Programmable Switching Frequency from 0.5MHz
to 2MHz
♦ Adjustable Outputs from 0.6V to (0.9 x V )
IN
Ordering Information
♦ Individual Enable Inputs and PWRGD Outputs
♦ Low-Cost Solution
PART
TYPE
MAX8855EVKIT+
EV Kit
♦ Fully Assembled and Tested
+Denotes lead(Pb)-free and RoHS-compliant.
Component Suppliers
SUPPLIER
Murata Electronics North America, Inc.
TDK Corp.
PHONE
WEBSITE
www.murata-northamerica.com
www.component.tdk.com
www.tokoam.com
770-436-1300
847-803-6100
847-297-0070
TOKO America, Inc.
Note: Indicate that you are using the MAX8855 when contacting these component suppliers.
Component List
DESIGNATION
QTY
DESCRIPTION
DESIGNATION
QTY
DESCRIPTION
2200pF 10ꢀ, 50V X7R ceramic
capacitor (0402)
TDK C1005X7R1H222K
Murata GRM155R71H222K
22µF 20ꢀ, 6.3V X5R ceramic
capacitors (1206)
TDK C3216X5R0J226M
Murata GRM31CR60J226K
C7
1
C1, C23
2
0.22µF 10ꢀ, 16V X5R ceramic
capacitor (0402)
TDK C1005X5R1C224K
0.1µF 10ꢀ, 16V X7R ceramic
capacitors (0402)
TDK C1005X7R1C104K
Murata GRM155R71C104K
C8
1
2
C2, C3, C4, C6,
C16, C17, C20
7
680pF 10ꢀ, 50V X7R ceramic
capacitors (0402)
TDK C1005X7R1H681K
Murata GRM1555R71H681K
C5
1
1
Not installed, capacitor
C9, C15
0.022µF 10ꢀ, 25V X7R ceramic
capacitor (0402)
C12
TDK C1005X7R1E223K
________________________________________________________________ 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.
MAX8855 Evaluation Kit
Component List (continued)
DESIGNATION
QTY
DESCRIPTION
DESIGNATION
QTY
DESCRIPTION
47pF 5ꢀ, 50V C0G ceramic
capacitors (0402)
TDK C1005C0G1H470J
Murata GRM1555C1H470J
0.47µH 20ꢀ inductors
TOKO FDV0630-R47M
L1, L2
2
C10, C14
2
R1, R19
R2
0
1
Not installed, resistors (0402)
0Ω resistor (0402)
560pF 10ꢀ, 50V X7R ceramic
capacitors (0402)
Murata GRM155R71H561K
R3, R4, R5, R12,
R13, R18
C11, C13
C18, C19
2
2
6
10kΩ 1ꢀ resistors (0402)
R6
R7, R10
R8, R9
R11
1
2
2
1
2
1
4.99kΩ 1ꢀ resistor (0402)
8.06kΩ 1ꢀ resistors (0402)
210Ω 1ꢀ resistors (0402)
10Ω 1ꢀ resistor (0402)
20kΩ 1ꢀ resistors (0402)
49.9Ω 1ꢀ resistor (1206)
Dual step-down regulator
(32 TQFN-EP*)
Maxim MAX8855ETJ+
47µF 20ꢀ, 6.3V X5R ceramic
capacitors (1206)
TDK C3216X5R0J476M
Murata GRM31CR60J476K
1000pF 10ꢀ, 50V X7R ceramic
capacitors (0402)
TDK C1005X7R1H102K
Murata GRM155R71H102K
R14, R15
R16
C21, C22
2
U1
1
FSYNC
JU1, JU3
JU2
0
2
1
Not installed, BNC connector
3-pin headers
Evluates:MAX85
—
2
1
Shunts, 2-position
2-pin header
—
PCB: MAX8855 EVALUATION KIT+
*EP = Exposed pad.
5) Connect the positive lead of a voltmeter to the
OUT1 pad and the negative lead of the voltmeter to
the PGND1 pad of the EV kit.
Quick Start
Recommended Equipment
• MAX8855 EV kit
6) Connect the positive lead of the other voltmeter to
the OUT2 pad and the negative lead of the volt-
meter to the PGND2 pad of the EV kit.
• Adjustable DC power supply capable of supplying
3.6V at up to 7A
• Two electronic loads capable of sinking 5A (e.g.,
HP 6060B)
7) Connect the positive lead of a 5A electronic load to
the OUT1 pad and the negative lead of the elec-
tronic load to the PGND1 pad of the EV kit.
• Two voltmeters (DMM)
8) Connect the positive lead of the second 5A elec-
tronic load to the OUT2 pad and the negative lead
of the electronic load to the PGND2 pad of the EV
kit.
Procedure
The 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:
9) Turn on the power supply.
1) Set the DC power supply in the 2.35V to 3.6V range
and turn off the power supply.
10) Verify that V
is 1.8V throughout the 2.35V to
OUT1
3.6V input voltage range.
2) Connect the positive lead of the power supply to
the IN pad and the negative pad to the PGND pad
of the EV kit.
11) Verify that V
is 1.2V throughout the 2.35V to
OUT2
3.6V input voltage range.
12) Turn on both electronic loads. Repeat steps 10 and 11.
3) Verify that JU1 and JU2 do not have a shunt installed.
4) Verify that a shunt is across pins 1 and 2 of jumper
JU3.
2
_______________________________________________________________________________________
MAX8855 Evaluation Kit
Evluates:MAX85
0V and V
- 1.6V to the REFIN pad to set the FB1 reg-
DD
Detailed Description
ulation voltage. To use the internal 0.6V reference,
place a shunt on JU3 pins 1-2 to connect REFIN to SS1
(see Table 3). When the IC is shut down, REFIN is
pulled to GND through an internal 335Ω.
The MAX8855 EV kit evaluates the MAX8855 dual step-
down regulator. The regulator switching frequency is
set to 1MHz by default and can be adjusted from
0.5MHz to 2MHz. The EV kit is designed to operate
from a DC power supply that can provide 2.35V to 3.6V
and 7A of current.
If additional filtering is required, a 0.22µF capacitor can
be added (C5).
Regulator 1 (OUT1) is configured as a step-down regu-
lator set to 1.8V and can provide 5A of current.
Regulator 2 (OUT2) is configured as a step-down regu-
lator set to 1.2V and can provide 5A of current.
Tracking
The EV kit can be configured as a tracking circuit (com-
monly used in DDR supply applications). To configure
the EV kit for tracking, install resistors R1 and R19.
These resistors form a voltage-divider that sets the
tracking ratio. Remove R6 so OUT1 regulates to the
REFIN voltage. Set jumper JU3 to pins 2-3. Refer to the
MAX8855 IC data sheet for more information on track-
ing circuits and component selection.
The EV kit output voltages are adjustable from a mini-
mum of 0.6V to a maximum of 0.9 x V . Refer to the
IN
Setting the Output Voltage section of the MAX8855 IC
data sheet to set other output voltages in this range for
V
OUT1
and V
.
OUT2
Sequencing
To enable sequencing on the EV kit, place a shunt on
pins 1-2 of JU1. In this configuration, OUT1 remains
disabled until OUT2 is enabled and reaches regulation.
When OUT1 is disabled, OUT2 shuts down at the same
time. Refer to the MAX8855 IC data sheet for more
information on sequencing.
Enable (EN1 and EN2)
The EV kit provides separate enable inputs, EN1 and
EN2, to individually control or sequence the output volt-
ages. The enable signals EN1 and EN2 are pulled up to
V
by resistors R3 and R18, respectively. To enable
DD
OUT1, remove the shunt from JU1; to disable OUT1,
place the shunt on JU1 pins 2-3. To enable OUT2,
remove the shunt from JU2; to disable OUT2, place the
shunt on JU2 pins 1-2.
Switching Frequency and
Synchronization (FSYNC)
The enable inputs can also be driven from an external
logic signal. With the JU1 and JU2 shunts removed,
connect the EN1 signal to pin 2 of JU1, and the EN2
signal to pin 2 of JU2. The device enable pins are
active-high and TTL compatible.
The EV kit operates from an internal 0.5MHz to 2MHz
switching frequency set by R5. The EV kit’s switching
frequency is set to 1MHz by default. To change the
switching frequency, replace R5 with a resistor value
calculated as shown in the Setting the Switching
Frequency section of the MAX8855 IC data sheet.
Power-Good Outputs (PWRGD_)
Regulator 1 and 2 provide power-good output signals
that indicate when the corresponding output is in regu-
lation. PWRGD1 and PWRGD2 are open-drain outputs
The EV kit can also be synchronized to an external
clock from 250kHz to 2.5MHz by connecting the clock
to the FSYNC BNC input. The external clock must have
a duty cycle between 10ꢀ and 90ꢀ to ensure the regu-
lators operate 180° out-of-phase.
that are pulled up to V
by a 20kΩ resistor. The
DD
power-good, open-drain output for regulator 1
(PWRGD1) is high impedance when V ≥ 0.54V
REFIN
Thermal-Overload Protection
Thermal-overload protection limits the total power dissi-
pation of the device. Internal thermal sensors monitor
the internal die temperature of each regulator. When this
temperature exceeds +165°C, the corresponding regu-
lator is shut down, allowing the IC to cool. The thermal
sensor turns the regulator on after the junction tempera-
ture cools by 20°C. In a continuous thermal-overload
condition, this results in a pulsed output.
and V
≥ 0.9 x V
. PWRGD1 is low when V
FB1
REFIN REFIN
< 0.54V, EN1 is low, V
or V
is below V
, the
DD
IN1
UVLO
thermal-overload protection is activated, or when V
FB1
< 0.9 x V
.
REFIN
PWRGD2 is high impedance when V
≥ 0.54V and
SS2
SS2
V
≥ 0.9 x V . PWRGD2 is low when V
< 0.54V,
FB2
SS2
DD
EN2 is low, V or V
is below V , the thermal-over-
UVLO
IN2
load protection is activated, or when V
< 0.9 x V
.
FB2
SS2
External Reference Input (REFIN)
The EV kit provides an option for an external reference
input. To use an external reference, remove the shunt
from JU3 and connect an external reference between
Current Limit
The EV kit provides both peak and valley current limits
to achieve robust short-circuit protection.
_______________________________________________________________________________________
3
MAX8855 Evaluation Kit
single input supply between 2.35V and 3.6V. VDL can
optionally be powered separately from the power input.
When powering VDL separately, remove resistor R2
and connect a 2.35V to 3.6V supply to the VDL pad on
the EV kit.
VDL Supply
VDL is the low-side gate-drive supply for the device.
The high-side gate drive (BST_) and the IC supply volt-
age (V ) are also derived from VDL. In the EV kit’s
DD
default configuration, VDL is connected to IN through
the 0Ω resistor R2, allowing the EV kit to operate from a
Table 1. Jumper JU1 Functions
Table 3. Jumper JU3 Functions
SHUNT
LOCATION
REFIN CONNECTED
TO
SHUNT
LOCATION
FUNCTION
EN1 CONNECTED TO
REGULATOR 1
Internal reference
(0.6V)
Not installed
(default)
Pulled up to V
through R3
DD
1-2 (default)
2-3
SS1
Enabled
OUT2 through R1
OUT1 tracks V
OUT2
Sequencing: OUT1 is
enabled when OUT2
is in regulation
1-2
2-3
PWRGD2
GND
External reference
(0V to V - 1.6V)
DD
connected to REFIN
pad
Not installed
—
Disabled
Evluates:MAX85
Table 2. Jumper JU2 Functions
SHUNT
LOCATION
EN2 CONNECTED TO
REGULATOR 2
Not installed
(default)
Pulled up to V
through R18
DD
Enabled
1-2
GND
Disabled
4
_______________________________________________________________________________________
MAX8855 Evaluation Kit
Evluates:MAX85
Figure 1. MAX8855 EV Kit Schematic
_______________________________________________________________________________________
5
MAX8855 Evaluation Kit
Evluates:MAX85
Figure 2. MAX8855 EV Kit Component Placement Guide—Component Side
6
_______________________________________________________________________________________
MAX8855 Evaluation Kit
Evluates:MAX85
Figure 3. MAX8855 EV Kit PCB Layout—Component Side
_______________________________________________________________________________________
7
MAX8855 Evaluation Kit
Evluates:MAX85
Figure 4. MAX8855 EV Kit PCB Layout—Layer 2
8
_______________________________________________________________________________________
MAX8855 Evaluation Kit
Evluates:MAX85
Figure 5. MAX8855 EV Kit PCB Layout—Layer 3
_______________________________________________________________________________________
9
MAX8855 Evaluation Kit
Evluates:MAX85
Figure 6. MAX8855 EV Kit PCB Layout—Solder Side
10 ______________________________________________________________________________________
MAX8855 Evaluation Kit
Evluates:MAX85
Revision History
REVISION REVISION
PAGES
CHANGED
DESCRIPTION
NUMBER
DATE
0
10/10
Initial release
—
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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 11
© 2010 Maxim Integrated Products
Maxim is a registered trademark of Maxim Integrated Products, Inc.
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