The MIC33263/4 evaluation board allows the customer to
evaluate a fully-integrated MOSFETs & Inductor 2A, 4MHz
synchronous buck regulator that features HyperLight
Load
®
mode, a Power Good output indicator, and
programmable soft-start. The MIC33263/4 is highly
efficient throughout the output current range. The tiny
2.5mm x 3mm QFN package, in combination with the
4MHz switching frequency, provides a compact sub-
1.9mm height solution and 7mm x 4.6mm total solution
size that requires few external components.
The MIC33263/4 has a maximum 100% duty cycle, and
the MIC33264 also incorporates an active discharge
feature when disabled. It provides accurate output voltage
regulation under the most demanding conditions and
responds extremely quickly to a load transient with
exceptionally small output voltage ripple.
Requirements
The MIC33263/4 evaluation board requires a single 15W
bench power source adjustable from 2.7V to 5.5V. The
loads can either be active (electronic load) or passive
(resistor), and must be able to dissipate 10W. It is ideal,
but not essential, to have an oscilloscope available to view
the circuit waveforms. The simplest tests require two
voltage meters to measure input and output voltages.
Efficiency measurements require two voltage meters and
two ammeters to prevent errors caused by measurement
inaccuracies.
Precautions
There is no reverse input protection on this board. Be
careful when connecting the input source to ensure correct
polarity is observed.
Datasheets and support documentation are available on
Micrel’s web site at:
www.micrel.com.
Getting Started
1. Connect an external supply to the V
IN
(J1) and GND
(J2) terminals.
With the output of the power supply disabled, set its
voltage to the desired input test voltage (2.7V ≤ V
IN
≤
5.5V). An ammeter may be placed between the input
supply and the V
IN
(J1) terminal. Be sure to monitor
the supply voltage at the V
IN
(J1) terminal, as the
ammeter and/or power lead resistance can reduce the
voltage supplied to the device.
2. Connect a load to the V
OUT
(J3) and GND (J4)
terminals.
The load can be either passive (resistive) or active
(electronic load). An ammeter may be placed between
the load and the output terminal. Make sure the output
voltage is monitored at the V
OUT
(J3) terminal.
3. Enable the MIC33263/4.
The MIC33263/4 evaluation board has a pull-up
resistor (R3) to V
IN
. By default, the output voltage is
enabled when the input supply of >2.7V is applied. To
disable the device, apply a voltage below 0.5V to the
EN (J6) terminal.
4. Power Good.
A PG test point (J5) is provided to monitor the Power
Good feature. The Power Good output will go high
(V
OUT
) approximately 90µs after the output voltage
reaches 92% of its nominal voltage.
Ordering Information
Part Number
MIC33263YGK EV
MIC33264YGK EV
Description
MIC33263 Evaluation Board
MIC33264 Evaluation Board
HyperLight Load is a registered trademark of Micrel, 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
May 6, 2014
Revision 1.0
Micrel, Inc.
MIC33263/4 Evaluation Board
V
OUT
1.2V
1.5V
1.8V
2.5V
3.3V
5V
R1
215k
301k
340k
274k
383k
634k
R2
301k
261k
215k
107k
102k
102k
Evaluation Board
The feedforward capacitor, C4, provides essential
compensation for the MIC33263/4. A typical value range of
15pF to 68pF is recommended.
Power Good (PG)
The evaluation board has a test point provided for testing
the Power Good feature. This is an open-drain connection
with an on-board pull-up resistor of 100kΩ (R4) to the
output voltage. Power Good is asserted high
approximately 90µs after the output voltage passes 92% of
the nominal set voltage.
HyperLight Load Mode
MIC33263/4 uses a minimum on and off time proprietary
control loop (patented by Micrel). When the output voltage
falls below the regulation threshold, the error comparator
begins a switching cycle that turns the PMOS on and
keeps it on for the duration of the minimum-on-time. This
increases the output voltage. If the output voltage is more
than the regulation threshold, then the error comparator
turns the PMOS off for a minimum-off-time until the output
drops below the threshold. The NMOS acts as an ideal
rectifier that conducts when the PMOS is off. Using an
NMOS switch instead of a diode allows for lower voltage
drop across the switching device when the NMOS is on.
The asynchronous switching combination between the
PMOS and the NMOS allows the control loop to work in
discontinuous mode for light load operations. In
discontinuous mode, the MIC33263/4 works in pulse
frequency modulation (PFM) to regulate the output. As the
output current increases, the off-time decreases. This
provides more energy to the output. This switching
scheme improves the efficiency of MIC33263/4 during light
load currents by only switching when it is needed.
As the load current increases, the MIC33263/4 goes into
continuous conduction mode (CCM) and switches at a
frequency centered at 4MHz.
Features
Soft-Start Capacitor (C3)
The soft start (SS) pin is used to control the output voltage
ramp-up time. Setting C3 to 1nF sets the start-up time to
the minimum. The start-up time can be determined by
Equation 1:
T
SS
=
250
×
10
3
×
ln(10 )
×
C
SS
Eq. 1
The action of the soft-start capacitor is to control the rise
time of the internal reference voltage between 0% and
100% of its nominal steady-state value.
Feedback Resistors (R1, R2)
The output voltage of the evaluation board is set to 2V.
This output can be changed by adjusting the upper
resistor, R1, in the feedback potential divider. The output
voltage can be programmed between 0.7V and 5V using:
R1
V
OUT
=
V
REF
×
1
+
R2
Where V
REF
= 0.7V
Table 1. Example Feedback Resistor Values
May 6, 2014
2
Revision 1.0
Micrel, Inc.
MIC33263/4 Evaluation Board
Evaluation Board Schematic
Bill of Materials
Item
C1
Part Number
C1608X5R1A475K080AC
GRM188R60J475KE19D
C1608X5R1A105K
Manufacturer
TDK
(1)
Murata
(2)
TDK
Description
4.7µF, 10V, X5R, Size 0603
Qty.
1
C2
1µF, 10V, X5R, Size 0603
1
C3
C1005C0G1H102J050BA
C1005C0G1H150J050BA
TDK
TDK
1nF, 50V, 0402
1
C4
GRM1555C1H150JZ01D
C5
C6
R1
R2
R3, R4
R5
U1
Notes:
1. TDK:
www.tdk.com.
2. Murata:
www.murata.com.
3. Vishay:
www.vishay.com.
4. Micrel, Inc.:
www.micrel.com.
15pF, 50V, 0402
Murata
TDK
TDK
Vishay
(3)
Vishay
Vishay
Vishay
Micrel, Inc.
(4)
22µF,10V, X5R, Size 0603
0.1µF,10V, X7R, Size 0603
301kΩ, 1%, 1/16W, Size 0402
158kΩ, 1%, 1/16W, Size 0402
100kΩ, 1%, 1/16W, Size 0402
49.9Ω, 1%, 1/16W, Size 0402
4MHz, 2A, 100% Duty Cycle Buck Regulator with
Integrated Inductor and HyperLight Load Technology
1
C1608X5R1A226M080AC
C1608X7R1A104K
CRCW0402301KFKEA
CRCW0402158K0FKEA
CRCW0402100KFKEA
CRCW040249R9FKED
MIC33163YGK
MIC33164YGK
1
1
1
1
2
1
1
May 6, 2014
3
Revision 1.0
Micrel, Inc.
MIC33263/4 Evaluation Board
PCB Layout
Top Layer
Bottom Layer
May 6, 2014
4
Revision 1.0
Micrel, Inc.
MIC33263/4 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
Micrel makes no representations or warranties with respect to the accuracy or completeness of the information furnished in this data sheet. This
information is not intended as a warranty and Micrel does not assume responsibility for its use. Micrel reserves the right to change circuitry,
specifications and descriptions at any time without notice. No license, whether express, implied, arising by estoppel or otherwise, to any intellectual
property rights is granted by this document. Except as provided in Micrel’s terms and conditions of sale for such products, Micrel assumes no liability
whatsoever, and Micrel disclaims any express or implied warranty relating to the sale and/or use of Micrel products including liability or warranties
relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right.
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.
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