MAX8625AEVKIT [MAXIM]
Programmable Output Voltage from 1.25V to 4.2V;
| 型号： | MAX8625AEVKIT |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Programmable Output Voltage from 1.25V to 4.2V |
| 文件： | 总7页 (文件大小：100K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-4153; Rev 2; 4/09
MAX8625A Evaluation Kit
Evluates:MX8625A
General Description
Features
The MAX8625A evaluation kit (EV kit) is a fully assem-
bled and tested PCB demonstrating the MAX8625A
step-up/step-down switching regulator. The MAX8625A
utilizes Maxim’s proprietary H-bridge topology that pro-
vides seamless transitions through all converter operat-
ing modes without the glitches commonly seen with
other similar devices. The MAX8625A EV kit converts a
2.5V to 5.5V DC input to a preprogrammed 3.3V output
capable of providing up to 800mA. The output voltage
is also programmable from 1.25V to 4.2V by use of a
resistor-divider. The MAX8625A EV kit provides on-
board jumper settings that allow programming one of
two switching modes: fixed-frequency PWM (FPWM) or
high-efficiency skip. Additional on-board jumpers allow
enable or shutdown of the MAX8625A IC.
♦ 2.5V to 5.5V Input-Voltage Range
♦ 3.3V Preset Output Voltage
♦ Programmable Output Voltage from 1.25V to 4.2V
♦ Glitch-Free Step-Up/Step-Down Transitions
♦ Selectable Switching Modes
FPWM Mode
High-Efficiency Skip Mode
♦ Soft-Start
♦ Output Overload Protection
♦ Thermal Protection
♦ Small 3mm x 3mm, 14-Pin TDFN IC Package
♦ Lead(Pb)-Free and RoHS Compliant
♦ Fully Assembled and Tested
Component List
Ordering Information
DESIGNATION QTY
DESCRIPTION
PART
TYPE
MAX8625AEVKIT+
EV Kit
22µF 20ꢀ% 10V X5R ceramic
capacitors (1206)
C1–C4
C5
4
1
2
2
+Denotes lead(Pb)-free and RoHS compliant.
Taiyo Yuden LMK316BJ226ML
0.1µF 10ꢀ% 16V X5R ceramic
capacitor (0402)
Taiyo Yuden EMK105BJ104KV
Component Suppliers
1µF 10ꢀ% 10V X5R ceramic
capacitors (0402)
Taiyo Yuden LMK105BJ105KV
SUPPLIER
PHONE
WEBSITE
C6% C7
JU1% JU2
Digi-Key Corp.
800-344-4539 www.digikey.com
760-744-0125 www.sullinselectronics.com
408-573-4150 www.t-yuden.com
408-432-8281 www.tokoam.com
Sullins Electronics
Corp.
3-pin headers
Sullins PEC36SAAN
Digi-Key S1012E-36-ND
Taiyo Yuden
TOKO America%
Inc.
3.3µH inductor
TOKO 1101AS-3R3M (DEA4012CK
series)
L1
1
0
Note: Indicate that you are using the MAX8625A when con-
tacting these component suppliers.
Not installed% resistors (0402)
R1 is open; R2 is short (PCB trace)
R1% R2
Step-up/down regulator (14 TDFN)
Maxim MAX8625AETD+
U1
—
1
1
PCB: MAX8625A EVALUATION KIT+
________________________________________________________________ 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.
MAX8625A Evaluation Kit
3) Connect the positive input of the DMM to the VOUT
pad on the EV kit, and the negative input of the
DMM to the GND pad on the EV kit to measure the
output voltage at VOUT.
Quick Start
Required Equipment
•
•
MAX8625A EV kit
One variable DC power supply capable of supply-
ing 2.5V to 5.5V at 2.5A
4) Connect an 800mA electronic load and ammeter
between the VOUT and GND pads on the EV kit.
•
•
•
One digital multimeter (DMM)
One ammeter
5) Ensure that shunts are placed on pins 2-3 of
jumpers JU1 and JU2 to enable the IC in FPWM
mode, as shown in Table 1.
One electronic load capable of sinking 800mA
6) Turn on the power supply.
Procedure
7) Verify that the voltage at VOUT is approximately
3.3V.
The MAX8625A EV kit is fully assembled and tested.
Follow these steps to verify board operation:
8) Sweep the voltage of the power supply between
2.5V to 5.5V and verify that the voltage at VOUT is
approximately 3.3V over the entire input range.
1) Preset the variable DC power supply to 3.3V. Turn
off the power supply. Caution: Do not turn on the
power supply until all connections are completed.
When evaluation of the MAX8625A EV kit is completed,
use the following steps to power down the EV kit:
2) Connect the positive lead of the power supply to the
VIN pad on the EV kit, and the negative lead of the
power supply to the GND pad on the EV kit.
1) Turn off the power supply.
2) Disconnect power supply, cables, and test leads
from the EV kit.
Evluates:MX8625A
Table 1. Jumper Settings
JUMPER
FUNCTION
Install a shunt across pins 2-3 to connect SKIP to IN for FPWM mode. Install a shunt across pins 1-2 to connect SKIP to
GND for skip mode. Do not switch the converter from FPWM (position 2-3) to SKIP (position 1-2) or vice versa on
the fly. The MAX8625A is not designed for dynamic transitions between skip and FPWM modes.
JU1
JU2
Install a shunt across pins 2-3 to enable the IC. Install a shunt across pins 1-2 to disable the IC. Enable the MAX8625A
after the supply voltage is above UVLO. Tying the ON pin to the supply and then ramping up the supply voltage is
not recommended.
2
_______________________________________________________________________________________
MAX8625A Evaluation Kit
Evluates:MX8625A
L1
3.3μH
1
2
3
4
VIN
2.5V TO 5.5V
VOUT
3.3V
LX1 LX1
LX2 LX2
OUT
13
14
9
IN
IN
C6
1μF
C7
1μF
C1, C2
22μF
C3, C4
22μF
10
OUT
U1
R1
OPEN
MAX8625A
3
2
1
6
7
JU1
JU2
SKIP
FB
R2
SHORT
GND
3
2
1
11
12
5
8
ON
GND
GND
REF
C5
0.1μF
Figure 1. MAX8625A EV Kit Schematic
Selecting the Switching Mode
Detailed Description of Hardware
The MAX8625A EV kit has two selectable switching modes:
1) Fixed-frequency PWM (FPWM) mode
2) High-efficiency skip mode
Setting the Output Voltage
The MAX8625A EV kit output voltage is preset at 3.3V,
but can be adjusted from 1.25V to 4.2V by the selection
of R1 and R2 resistance values (Figure 1). To program
the output voltage, follow the procedure below:
Fixed-Frequency PWM Mode (FPWM)
In FPWM mode, the MAX8625A operates at a constant
1MHz switching frequency with no pulse skipping. This
scheme is desirable in noise-sensitive applications
because the output ripple frequency spectrum is mini-
mized and predictable. FPWM mode consumes higher
supply current at light loads due to constant switching.
1) Select a 100kΩ resistance value for R2.
2) Determine the value of R1 from the following equation:
⎛
⎞
V
V
OUT
R1 = 100kΩ ×
− 1
⎟
⎜
⎝
⎠
FB
High-Efficiency Skip Mode
In skip mode, the IC switches only as necessary to
maintain the output in regulation at light loads, but still
operates with fixed-frequency PWM at medium and
heavy loads. This operation maximizes light-load effi-
ciency and reduces the input quiescent current.
where V = 1.25V and V
is the desired output
FB
OUT
regulation voltage. V
and 4.2V.
must be between 1.25V
OUT
3) Cut the trace shorting the pads of resistor R2.
4) Install resistors R1 and R2 on the MAX8625A EV kit.
To select the switching mode, shunt jumper JU1 on the
MAX8625A EV kit as indicated in Table 1.
Note: Adjusting the output voltage affects the maximum
output current available from the MAX8625A EV kit and
may require changing the value of inductance of L1.
Refer to the Applications Information section in the
MAX8625A IC data sheet for more information.
Selecting Shutdown Mode
To place the MAX8625A in shutdown mode, shunt pins
1-2 of jumper JU2 on the MAX8625A EV kit. To enable
the MAX8625A, shunt pins 2-3 of jumper JU2 on the
MAX8625A EV kit.
_______________________________________________________________________________________
3
MAX8625A Evaluation Kit
Evluates:MX8625A
Figure 2. MAX8625A EV Kit Component Placement Guide—Top Silkscreen
4
_______________________________________________________________________________________
MAX8625A Evaluation Kit
Evluates:MX8625A
Figure 3. MAX8625A EV Kit PCB Layout—Component Side
_______________________________________________________________________________________
5
MAX8625A Evaluation Kit
Evluates:MX8625A
Figure 4. MAX8625A EV Kit PCB Layout—Solder Side
6
_______________________________________________________________________________________
MAX8625A Evaluation Kit
Evluates:MX8625A
Revision History
REVISION REVISION
PAGES
DESCRIPTION
CHANGED
NUMBER
DATE
0
1
5/08
Initial release
Modified the jumper settings in Table 1
—
11/08
2
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 _____________________ 7
© 2009 Maxim Integrated Products
Maxim is a registered trademark of Maxim Integrated Products, Inc.
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