MIC4744YML Evaluation Board

MIC4744YML Evaluation Board
Dual 2A Buck Regulator
General Description
The Micrel MIC4744 is a high efficiency dual PWM buck
(step-down) regulator that provides up to 2A of output
current for each channel. The MIC4744 operates at 4MHz
and has proprietary internal compensation that allows a
closed loop bandwidth of over 200kHz. The low on
resistance internal P-Channel MOSFET of the MIC4744
allows efficiencies up to 90%, reduces external component
count and eliminates the need for an expensive external
current sense resistor. The MIC4744 operates from a 2.9V
to 5.5V input and its output is adjustable down to 0.6V.
The devices can operate with a maximum duty cycle of
100% for use in low-dropout applications.
3. Enable the MIC4744. The enable pins are connected
to pull up resistors. Both outputs of the MIC4744 turn
on when VIN exceeds the UVLO threshold at the VIN pin.
Each output of the MIC4744 may be turned off by
shorting the enable 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.
Output Voltage
The output voltages on the MIC4744 evaluation board are
adjustable. The output voltage is controlled by the
feedback resistors (R11 and R12 for VOUT1, R21 and R22
for VOUT2) and can be calculated as follows:
Requirements
VOUT 1 = VREF × (1 +
R11
)
R12
The MIC4744 evaluation board requires an input power
source that is able to deliver greater than 2.9V at over 4A.
The output load can either be an active or passive load.
VOUT 2 = VREF × (1 +
R 21
)
R 22
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 MIC4744 evaluation board is 5.5V.
Exceeding 6V on the input could damage the device.
Where VREF = 0.6V.
The evaluation board is preset at 1.8V for VOUT1 and 1.2V
for VOUT2, but can easily be modified by removing R12 or
R22 and replacing them with the value that yields the
desired output voltage.
R12 =
R11 × VREF
VOUT − VREF
R 22 =
R 21 × VREF
VOUT − VREF
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 (2.9V<VIN<5.5V). 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 VOUT1/VOUT2 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 VOUT1/VOUT2 terminal.
Ensure the output voltage is monitored at the
VOUT1/VOUT2 terminal. The default VOUT1 is set to 1.8V
and the default VOUT2 is set to 1.2V. This can be
adjusted by changing the feedback resistors. See
“Output Voltage.”
For VREF = 0.6V, this reduces to:
R12 =
R11 × 0.6V
VOUT − 0.6V
R 22 =
R 21 × 0.6V
VOUT − 0.6V
Ordering Information
Part Number
Description
Package
MIC4744YML
IC
16-Pin EPAD-MLF®
MIC4744YML EV
Evaluation Board
16-Pin EPAD-MLF®
MLF is a registered trademark of Amkor Technology, Inc.
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
February 2009
M9999-021709-B
Micrel, Inc.
MIC4744YML Evaluation Board
Evaluation Board Schematic
Bill of Materials
Item
Part Number
C11,C12
GRM188R60J106M
C21,C22
C1608X5R0J106M
Manufacturer
TDK(2)
10µF Ceramic Capacitor, X5R, Size 0603, 6.3V
6
680pF Ceramic Capacitor, NPO, Size 0603, 6.3V
2
Vishay
82pF Ceramic Capacitor, NPO Size 0603, 10V
2
VJ0603Y104KXXAT
Vishay(4)
0.1µF Ceramic Capacitor, X7R, Size 0603, 25V
5
SS2P3L
Vishay(4)
SSA23L
Vishay(4)
2A Schottky 30V
2
0.47µH Inductor 20mΩ 4.45mm(L) x 4.06mm(W) x 1.2 mm(H)
2
10kΩ, 1%, Size 0603 Resistor
2
06036D106KMAT2A
C13*,C23*
VJ0603A681KXXCW
Vishay(4)
VJ0603A820KXXCW
(4)
C18,C28
D1,D2
C16,C26,C7
L1,L2
(3)
AVX
(5)
B230A
Diodes
IHLP1616AB-01 R47
Vishay(4)
R11,R12
CRCW060310K0FKXX
R12,R22
CRCW06033K16FKXX
(4)
Vishay
3.16kΩ, 1%, Size 0603 Resistor For 2.5VOUT
CRCW06034K99FKXX
CRCW06036K65FKXX
February 2009
Qty
Murata
C15,C25
C14,C24
Description
(1)
4.99kΩ, 1%, Size 0603 Resistor For 1.8 VOUT
(4)
Vishay
6.65kΩ, 1%, Size 0603 Resistor For 1.5 VOUT
CRCW060310K0FKXX
10kΩ, 1%, Size 0603 Resistor For 1.2 VOUT
CRCW060315K0FKXX
15kΩ, 1%, Size 0603 Resistor For 1.0 VOUT
2
2
M9999-021709-B
Micrel, Inc.
MIC4744YML Evaluation Board
Bill of Materials (continued)
Item
R13*, R23*
R14, R24
R5
U1
Part Number
CRCW06032R70FKXX
CRCW060349K9FKXX
CRCW060310R0FKXX
MIC4744YML
Manufacturer
Description
Qty
(4)
2.7Ω, 1%, Size 0603 Resistor
2
(4)
49.9kΩ, 1%, Size 0603 Resistor
2
10Ω, 1%, Size 0603 Resistor
1
Dual 2A 2MHz Integrated Switch Buck Regulator
1
Vishay
Vishay
(4)
Vishay
Micrel, Inc.
(7)
Notes:
1. Murata: www.murata.com
2. TDK: www.tdk.com
3. AVX: www.avx.com
4. Vishay: www.vishay.com
5. Cooper: www.cooperbussmann.com
6. Diode: www.diodes.com
7. Micrel, Inc: www.micrel.com
*only for ultra-low noise applications.
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Micrel, Inc.
MIC4744YML Evaluation Board
Printed Circuit Board Layouts
Figure 1a. Top Layer
Figure 1b. Bottom Layer
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M9999-021709-B
Micrel, Inc.
MIC4744YML Evaluation Board
Figure 1c. Mid-Layer 1
Figure 1d. Mid-Layer 2
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
The 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.
February 2009
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