MAX1927EVKIT [MAXIM]
Evaluation Kit for the MAX1927/MAX1928 ; 评估板MAX1927 / MAX1928\n
| 型号： | MAX1927EVKIT |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Evaluation Kit for the MAX1927/MAX1928
|
| 文件： | 总4页 (文件大小：119K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-2642; Rev 0; 10/02
MAX1927/MAX1928 Evaluation Kit
General Description
Features
The MAX1927/MAX1928 evaluation kit (EV kit) is a fully
assembled and tested surface-mount circuit board
demonstrating the MAX1927/MAX1928 pulse-width
modulated (PWM) step-down converters. The EV kit
comes assembled with a MAX1928EUB18, which steps
down a 2.6V to 5.5V input to a 1.8V output capable of
sourcing 800mA. This EV kit can also be used to evaluate
the MAX1927 with minor PC board modifications.
o 2.6V to 5.5V Input Voltage Range
o 1.8V Output Voltage (MAX1928EUB18)
o Up to 800mA Output Current
o 1MHz PWM Operation
o 100% Duty-Cycle Operation for Low Dropout
o No Current-Sense Resistor Needed
o Power-OK Output
The MAX1927/MAX1928 optimize efficiency and battery
life by skipping pulses at low loads. They feature a
forced-PWM mode for low output noise and contain
internal MOSFETs for minimum cost and size. A 1MHz
switching frequency allows the use of small external
components.
o 93% Efficiency
o Internal MOSFET Switch and Synchronous
Rectifier
o Soft-Start
o Surface-Mount Components
o Fully Assembled and Tested
Component List
DESIGNATION QTY
DESCRIPTION
10µF 20%, 6.3V X5R ceramic
capacitors
Taiyo Yuden JMK212BJ106MG
Ordering Information
C1, C2
C3
2
1
1
1
PART
TEMP RANGE
IC PACKAGE
MAX1928EVKIT
-40°C to +85°C
10 µMAX
1200pF 10%, 50V X7R ceramic
capacitor
Murata GRM188R71H102K
Note: To evaluate the MAX1927REUB, MAX1928EUB15, or
MAX1928EUB25, request a MAX1927REUB or MAX1928EUBXX
free sample with the MAX1927/MAX1928 EV kit.
0.1µF 10%, 16V X7R ceramic
capacitor
Taiyo Yuden EMK107BJ104KA
Required Equipment
Before beginning, the following equipment is required:
• 2.6V to 5.5V, 1A, variable-output power supply
• Dummy load capable of sinking 800mA
• Digital multimeter (DMM)
C4
22pF 5%, 50V COG ceramic
capacitor
Murata GRM1885C1H270J
C5
JU1, JU2
L1
2
1
Jumpers, SIP3, 3-pin headers
Quick Start
4.7µH, 900mA power inductor
Sumida CDRH4D18-4R7
The MAX1927/MAX1928 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:
R1
R2, R3, R5
R4
1
2
1
1
2
18k
5% resistor
Not installed
1M
5% resistor
1) Preset the power supply to 5V, and turn off the
power supply.
U1
MAX1928EUB18
Shunts
2) Verify that the shunt is across JU2 pins 2 and 3 for
normal-mode (not fixed-PWM) operation.
None
Component Suppliers
SUPPLIER
COMPONENT
Capacitors
Inductors
PHONE
WEBSITE
www.murata.com
Murata
Sumida
770-436-1300
81-03-3667-3381
408-573-4150
www.sumida.com
www.t-yuden.com
Taiyo Yuden
Capacitors
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
MAX1927/MAX1928 Evaluation Kit
3) Verify that the shunt is across JU1 pins 1 and 2 to
enable the device.
for each output voltage. Refer to the Stability and
Compensation section in the MAX1927/MAX1928 data
sheet for instructions on calculating compensation
components.
4) Connect the positive lead of the power supply to VIN,
and the negative lead of the power supply to GND.
5) Connect the positive input of the DMM to VOUT,
and the negative input of the DMM to GND to mea-
sure the output voltage.
Operating Modes
The MAX1927/MAX1928 operate in one of two modes.
Normal mode (PWM = GND) utilizes PWM at loads
greater than 130mA. At lighter loads, pulses are skipped
in order to maximize efficiency and battery life. Forced-
PWM mode forces PWM operation, regardless of load,
so that output ripple remains at a fixed frequency for
easier noise filtering. Place a shunt between positions
1 and 2 of JU2 for forced-PWM operation, or place a
shunt between positions 2 and 3 of JU2 for normal
PFM/PWM operation.
6) Turn on the power supply and sweep the input volt-
age from 2.6V to 5.5V.
7) Verify that the output voltage is 1.8V over the entire
input range.
8) Connect the 800mA load between VOUT and GND.
9) Verify that the output voltage is 1.8V.
Detailed Description
Evaluating Other Output Voltages
The MAX1927R is used for an adjustable output volt-
age. To set the adjustable output, cut the trace that
POK Output
The MAX1927/MAX1928 have an open-drain power-OK
(POK) output that goes high impedance 20ms after the
output is in regulation. On the EV kit, R4 pulls up POK
to VIN. Alternately, POK can be pulled up to VOUT by
moving the 1M resistor at R4 to the R5 location.
shorts R2 and place a 51k
calculated as:
1% resistor at R3. R2 is
Shutdown
The MAX1927/MAX1928 feature a shutdown mode to
power down the output and reduce input current. To
shut down the device, place a shunt between positions
2 and 3 of JU1. To operate normally, place a shunt
between positions 1 and 2 of JU1.
R2 = 51,000 ✕ ((V
/ V ) - 1)
OUT
FB
where V
is 0.75V and V
OUT
is the desired output
OUT
FB
voltage. V
can never exceed V . Compensation
IN
components R1, C3, and C5 may need to be optimized
Jumper Settings
Jumper JU2 Functions (PWM Control)
SHUNT
Jumper JU1 Functions (SHDN Control)
SHUNT
PWM
OPERATION
SHDN
OPERATION
LOCATION
LOCATION
1 and 2
2 and 3
Connected to VIN Normal operation
Connected to GND Shutdown
Forced-PWM mode
at all loads
Between 1 and 2
Connected to VIN
Skips pulses at light
loads, PWM at loads
above 130mA
Between 2 and 3 Connected to GND
2
_______________________________________________________________________________________
MAX1927/MAX1928 Evaluation Kit
JU2
1
2 3
VIN
2.6V TO 5.5V
L1
1
8
9
VOUT
1.8V
PWM
LX
BATT
CDRH4D18-4R7
4.7 H
C1
10 F
R1
U1
18k
5
6
3
C2
COMP
SHDN
C3
1200pF
C5
4
10 F
MAX1928EUB18
R2
OPEN
FB
22pF
POK
10
7
POK
GND
PGND
REF
R3
OPEN
GND
2
C4
0.1 F
JU1
1
2 3
SHDN
R4
1M
R5
OPEN
VIN
VOUT
Figure 1. MAX1928 EV Kit Schematic
_______________________________________________________________________________________
3
MAX1927/MAX1928 Evaluation Kit
mils
mils
mils
mils
Figure 2. MAX1928 EV Kit Component Placement Guide—Top
Silkscreen
Figure 3. MAX1928 EV Kit PC Board Layout—Component Side
mils
mils
Figure 4. MAX1928 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
© 2002 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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