MIC4724YMME Evaluation Board User Guide

MIC4724YMME Evaluation Board
3A Buck Regulator
General Description
The Micrel MIC4724 is a high efficiency PWM buck
(step-down) regulator that provides up to 3A of output
current. The MIC4724 operates at 2MHz and has
proprietary internal compensation that allows a closed
loop bandwidth of over 200kHz. The low onresistance internal P-Channel MOSFET of the
MIC4724 allows efficiencies up to 94%, reduces
external component count and eliminates the need for
an expensive external current sense resistor. The
MIC4724 operates from a 3V to 6V input and its
output is adjustable down to 1V. The devices can
operate with a maximum duty cycle of 100% for use
in low-dropout applications.
Requirements
The MIC4724 evaluation board requires an input
power source that is able to deliver greater than 3V at
over 3A. The output load can either be an active or
passive load.
Precautions
The evaluation board does not have reverse polarity
protection. Applying a negative voltage to the VIN
terminal may damage the device. In addition, the
maximum operating voltage of the MIC4724
evaluation board is 6V. Exceeding 6.5V on the input
could damage the device. For short circuit testing,
an additional input capacitor over 22µF is
required when using the demo board. This is
preferably an electrolytic, but may be tantalum or
ceramic. The inductance of long test leads connecting
the supply voltage to the demo board can be over
1µH.
During a short circuit condition, the high peak currents
through the test leads may cause the input voltage to
spike high and exceed the absolute maximum rating
of 6V, possibly damaging the device.
Getting Started
1. Connect an external supply to VIN
terminal. Apply desired input voltage to the
VIN and ground terminals of the evaluation
board, paying careful attention to polarity
and supply voltage (3V<VIN<6.5V). An
ammeter may be placed between the input
supply and the VIN terminal to the evaluation
board. Ensure the supply voltage is
monitored at the VIN terminal. The ammeter
and/or power lead resistance can reduce the
voltage supplied to the input.
2. Connect the load to the VOUT and ground
terminals. The load can be either passive
(resistive) or active (as in an electronic
load). An ammeter can be placed between
the load and the VOUT terminal. Ensure the
output voltage is monitored at the VOUT
terminal. The default output voltage is set to
1.8V. This can be adjusted by changing the
feedback resistors. See “Output Voltage.”
3. Enable the MIC4724. The enable pin is
connected to a pull up resistor. The
MIC4724 turns on when VIN exceeds the
UVLO threshold at the VIN pin. The MIC4724
may be turned off by shorting the pin to
ground or bringing the enable pin below the
enable threshold. An external connection on
the board provides easy access to the
enable pin.
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax 1 (408) 474-1000 • http://www.micrel.com
June 2008
M9999-062408-A
Micrel, Inc.
MIC4724YMME Evaluation Board
Output Voltage
The output voltage on the MIC4724 evaluation board
is adjustable. The output voltage is controlled by the
feedback resistors (R1 and R2) and can be calculated
as follows:
Power OK
The POK pin is pulled up to VIN through a pull-up
resistor and is asserted low when VOUT is within the
regulation band. An external connection on the
board provides easy access to the POK pin.
R1 ⎞
⎛
VOUT = VREF × ⎜1 +
⎟
R2 ⎠
⎝
Ordering Information
Where VREF = 1V.
The evaluation board is preset at 1.8V, but can
easily be modified by removing R2 and replacing it
with the value that yields the desired output voltage.
(Removing R2 sets the output to 1V).
R2 =
R1 × VREF
VOUT − VREF
Part Number
Description
Package
MIC4724YMME
IC
10-Pin MSOP
EPAD
MIC4724YMME EV
Evaluation Board
10-Pin MSOP
EPAD
For VREF = 1V, this reduces to:
R2 =
June 2008
R1
VOUT − 1
2
M9999-062408-A
Micrel, Inc.
MIC4724YMME Evaluation Board
U1
MIC4724YMME
2
R6
49.9k
R5
10k
C1
10µF
C2
10µF
/6.3V
9
VIN
SW
VIN
SW
1
L1
1µH
10
1
J1
+VIN
R3
6
J4
PGOOD
7
EN
PGOOD
BIAS
8
C3
0.1µF
/10V
AGND
4
FB
C5
82pF
R1
10k
5
C4
680pF
3
R
PGND
2
J3
EN
J5
VOUT
1.8V@3A
D1
SSA33L
C6
4.7µF
R2
12.4K
J6
GND
J2
GND
Bill of Materials
Item
Part Number
C1608 X5R0J106K
Manufacturer
TDK(1)
C1, C2
GRM188R61A106K
08056D106MAT
JMK107BJ106MA-T
Murata(2)
AVX(3)
Taiyo Yuden(4)
VJ0402Y104KXQCW1BC
Vishay(5)
10µF Ceramic Capacitor X5R 6.3V
10µF Ceramic Capacitor X5R 6.3V
0.1µF Ceramic Capacitor X7R 10V
C1005X7R1A104K
TDK(1)
0.1µF Ceramic Capacitor X7R 10V
C3
0402ZD104MAT
C4
C5
C6
(3)
680pF Ceramic Capacitor NPO 10V
C1005COG1A681J
TDK(1)
680pF Ceramic Capacitor 10V
VJ0402A82KXXCW1BC
Vishay(5)
82pF Ceramic Capacitor NPO 10V
(1)
C1005COG1A820J
TDK
C1608X5R0J475K
06036D475MAT
TDK(1)
AVX(3)
JMK107BJ475MA-T
GRM188R60J475KE19D
Taiyo Yuden(4)
Murata(2)
SSA33L
Vishay(5)
MBRM330-13
Diodes, Inc.(6)
LTF5022T-1R2N4R2
TDK(1)
IHLP2525AHER1R0M01
U1
MIC4724YMME
Micrel, Inc.(7)
2
1
3
1
1
3A Schottky 30V
1
1µH Inductor 7A
Vishay Dale(5)
1
4.7µF Ceramic Capacitor X5R 6V
1.2µH Inductor 4.3A ±30%
Vishay
R2
R3
R4
R6
June 2008
82pF Ceramic Capacitor 10V
(5)
Vishay Dale(5)
Qty.
0.1µF Ceramic Capacitor X5R 10V
AVX
Vishay(5)
CRCW04021002FKEYE3
CRCW04021242FKEYE3
CRCW04022R70FKEYE3
CRCW040210R0FKEYE3
CRCW04024992FKEYE3
R1, R5
10µF Ceramic Capacitor X5R 10V
VJ0402A681KXXCW1BC
D1
L1
Description
10µF Ceramic Capacitor X5R 6.3V
1
10k 1% 0402 1/16W
2
12.4k 1% 0402 1/16W
2.7Ω 1% 0402 1/16W
10Ω 1% 0402 Resistor
1
1
1
49.9k 1% 0402 Resistor
2MHz 3A Buck Regulator
1
1
M9999-062408-A
Micrel, Inc.
MIC4724YMME Evaluation Board
Notes:
1. TDK: www.tdk.com
2. Murata: www.murata.com
3. AVX: www.avx.com
4. Taiyo Yuden: www.t-yuden.com
5. Vishay: www.vishay.com
6. Diodes, Inc.: www.diodes.com
7. Micrel, Inc.: www.micrel.com
June 2008
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M9999-062408-A
Micrel, Inc.
MIC4724YMME Evaluation Board
Printed Circuit Board Layouts
Figure 1a. Top Layer
Figure 1b. Bottom Layer
June 2008
5
M9999-062408-A
Micrel, Inc.
MIC4724YMME Evaluation Board
MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http:/www.micrel.com
This information furnished by Micrel in this data sheet is believed to be accurate and reliable. However no responsibility is assumed by Micrel for
its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.
Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a
product can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for
surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant
injury to the user. A Purchaser's use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser's own risk
and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale.
© 2008 Micrel Incorporated
June 2008
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M9999-062408-A