MIC22700YML Evaluation Board User Guide

MIC22700YML Evaluation Board
Integrated 7A Synchronous Buck
Regulator
General Description
The Micrel MIC22700 is a high-efficiency, 7A, integrated,
synchronous buck (step-down) regulator. The MIC22700 is
optimized for highest power density and achieves over
90% efficiency while switching at 1MHz with only 1µH
inductor and 100µF output capacitor. The MIC22700
features integrated 7A MOSFETs, flexible sequencing and
tracking abilities.
This board enables the evaluation of the MIC22700; a high
power density, synchronous buck regulator. The board is
optimized for ease of testing, with all the components on a
single side. The voltage-mode feedback loop is designed
to allow high bandwidth with just two external
compensation components. The high-side MOSFET is a
P-Channel, allowing duty cycle control up to 100%. The
ultra-high-speed control loop keeps the output voltage
within regulation even under extreme transient load swings
commonly found in FPGAs and low voltage ASICs. The
output voltage can be adjusted down to 0.7V to address all
low voltage power needs. The MIC22700 offers a fullrange of sequencing and tracking options. The
enable/delay pin combined with the Power Good/Poweron-Reset (PG/POR) pin allows multiple outputs to be
sequenced in any way on turn-on and turn-off. The RC
(Ramp Control™) pin allows the device to be connected to
another MIC22700 device to keep the output voltages
within a certain delta V on start-up.
Requirements
This board needs a single bench power source adjustable
over the input voltage of 2.6V< VIN < 5.5V that can provide
at least 7A of current. The loads can either be active
(electronic load) or passive (resistor) with the ability to
dissipate the maximum load power while keeping
accessible surfaces ideally < 70°C.
Precautions
There is no reverse input protection on this board. When
connecting the input sources, ensure that the correct
polarity is observed.
Under extreme load conditions such as short circuit
testing, input transients can be quite large if long test leads
are used. In such cases, place a 100µF, 6.3V Tantalum
capacitor at the VIN terminals to prevent over voltage
damage to the IC.
Getting Started
1. Connect VIN supply to the input terminals +VIN
and GND. With the output of this supply disabled,
set its voltage to the desired input test voltage
(2.6V< VIN < 5.5V). This supply voltage should be
monitored at the test boards input terminals to
allow voltage drops in the test cables (and
ammeter if used) to be accounted for. An ammeter
can be added inline with the +VIN input terminal to
accurately measure input current.
2. Connect the loads to the output terminals
between +VO and GND. Again, this output voltage
should be monitored by connecting the voltmeter
at the +VO and GND terminals. An ammeter can
be added inline with the +VO terminal of the
evaluation board to accurately measure the output
current.
Output voltage is set to 1.8V. Output voltage can
be changed by selecting the resistor R2.
The resistor divider network for a desired VOUT is
given by:
R2 =
R1
⎛ VOUT
⎜
⎜V
⎝ REF
⎞
⎟
⎟
⎠
−1
where VREF is 0.7V and VOUT is the desired output
voltage.
Initially, set the output load to 0A to check that the
output is regulating properly prior to loaded tests.
3. Enable the input supply. By default, the output
voltage is enabled when an input supply of > 2.5V
is applied. When this threshold is crossed, the
enable pin capacitor (1nF) begins to charge at
1V/µs until it reaches 1.25V, where switching
begins. To test the enable functions of the
MIC22700, a test point is provided.
Ordering Information
Part Number
Description
MIC22700YML EV
Evaluation board with the integrated
7A MIC22700 device
Ramp Control is a 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
June 2011
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Micrel, Inc.
MIC22700YML Evaluation Board
Other Features
Power-on-Reset (POR) Delay Time Input
Adding an external capacitor to this Delay pin allows the
Power Good delay to be adjusted to perform as a Poweron-Reset (POR). As with the RC pin, this pin has an
internal 1µA current source and sink. When VFB reaches
90% of its nominal voltage (~630mV) the internal 1µA
current source charges the capacitor on this pin (C8) to the
rising threshold of 1.25V, at this point, PG is asserted high.
When the enable pin is set low, POR is asserted low
immediately. However, the internal ‘Delay’ current sink
discharges the capacitor (C8) to 1.25V lower than its
starting point, at which point, it enables the RC pin 1µA
current sink to begin discharging capacitor C7.
Enable Delay Input
C6 creates a delay set by an internal 1µA source charging
to a 1.25V threshold. A switch (Q1) is used from EN pin to
ground as shutdown ‘SHDN’ control. The part will exhibit
approximately 1.3µs enable delay from ‘SHDN’ going low
to the start of switching. Using a pulse generator with a low
impedance output connected to the EN terminal will
remove this delay as it defeats the internal 1µA source.
RC (Ramp Control™) Capacitor
The MIC22700 has a nominal 1µA current source/sink to
the RC pin. The startup output voltage waveform tracks
the voltage on RC. 100% output voltage is represented by
0.7V on RC. The default capacitor on RC (C7) of 10nF
sets the ramp up time to approximately 700µs.
Power-on-Reset (POR) Output
This is an open drain connection with an on board pull-up
resistor (R3) to SVIN. This is only asserted high when the
FB pin reaches >90% of its nominal set voltage. This can
be used as part of the tracking and sequencing function
described in the data sheet.
Feedback resistors
The output is set nominally at 1.8V. This can be changed
by adjusting the upper or lower resistor in the FB potential
dividers. It is recommended that R1 or R2 value should be
kept <10k to reduce noise susceptibility and offset currents
from creating voltage errors. Therefore, choosing R1<10k:
R2 = R1 × VREF/(VO – VREF)
where VREF = 0.7V.
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MIC22700YML Evaluation Board
Evaluation Board Performances
Efficiency @ 1.8VOUT
100
95
90
85
80
75
100
95
90
3.3VIN
5.5VIN
85
80
75
70
65
70
65
60
55
60
55
50
0
June 2011
2.6VIN
Efficiency @ 3.3VOUT
50
0
1234567
LOAD CURRENT (A)
3
VIN = 5.5V
1234567
LOAD CURRENT (A)
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Micrel, Inc.
MIC22700YML Evaluation Board
Evaluation Board Schematic
Bill of Materials
Item
Part Number
Manufacturer
C2012X5R0J226M
TDK
08056D226MAT
AVX(2)
C1, C2,
C3, C4,
C5
GRM21BR60J226ME39L
Murata
C7, C13
GRM188R71H103KA01D
Murata(3)
C6
C8
C12
June 2011
22µF/6.3V, 0805 Ceramic Capacitor
5
10nF, 0603 Ceramic Capacitor
1
(3)
(4)
Vishay
Open (GRM188R71H102KA01D)
Murata(3)
1000pF/50V, X7R, 0603 Ceramic
Capacitor
Open (C1608C0G1H102J)
TDK(1)
1000pF/50V, COG, 0603 Ceramic
Capacitor
VJ0603Y102KXQCW1BC
Vishay(4)
1nF, 0603 Ceramic Capacitor
GRM188R71H102KA01D
Murata(3)
1000pF/50V, X7R, 0603 Ceramic
Capacitor
TDK(1)
1000pF/50V, COG, 0603 Ceramic
Capacitor
GRM1555C1H390JZ01D
Murata(3)
VJ0402A390KXQCW1BC
BC Components
C3216X5R0J476M
C10, C11
Qty.
Open (VJ0603Y102KXQCW1BC)
C1608C0G1H102J
C9
Description
(1)
TDK(1)
1nF, 0603 Ceramic Capacitor
1
1
39pF/50V, COG, 0402, Ceramic
Capacitor
1
39pF/10V, 0402, Ceramic Capacitor
47µF/6.3V, X5R, 1206, Ceramic
Capacitor
GRM31CR60J476ME19
Murata(3)
47µF/6.3V, X5R, 1206 Ceramic Capacitor
GRM31CC80G476ME19L
Murata(3)
47µF/4V, X6S, 1206 Ceramic Capacitor
VJ0402A101KXQCW1BC
(4)
Vishay
100pF, 0603 Ceramic Capacitor
GRM1555C1H101JZ01D
Murata(3)
100pF/50V, COG, 0402, Ceramic
Capacitor
4
2
1
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MIC22700YML Evaluation Board
Bill of Materials (Continued)
Item
D1
Part Number
SS2P2L
DFLS220
SPM6530T-1R0M120
L1
HCP0704-1R0-R
R1
R2
R3
R4
R5
U1
Description
Qty.
(4)
Vishay
Diodes, Inc.(5)
TDK(1)
Coiltronics
2A, 20V Schottky Diode
1
1µH, 12A, size 7mm × 6.5mm × 3mm
1µH, 12 A, size 6.8mm × 6.8mm × 4.2mm
1
CRCW06031101FKEYE3
Vishay(4)
1.1k, 0603 Resistor, 1%
1
CRCW04026980FKEYE3
(4)
698Ω, 0603 Resistor, 1%
1
(4)
47.5k, 0603 Resistor, 1%
1
(4)
20k, 0402 Resistor, 1%
1
(4)
100k, 0603 Resistor, 1%
1
Signal MOSFET – SOT-23-6
1
Integrated 7A Synchronous Buck
Regulator
1
CRCW06034752FKEYE3
CRCW04022002FKEYE3
Open (CRCW06031003FRT1)
Open (2N7002E)
Q1
Manufacturer
Open(CMDPM7002A)
MIC22700YML
Vishay
Vishay
Vishay
Vishay
(4)
Vishay
Central
Semiconductor (5)
Micrel(6)
Notes:
1.
TDK: www.tdk.com.
2.
AVX: www.avx.com.
3.
Murata: www.murata.com.
4.
Vishay: www.vishay.com.
5.
Central Semiconductor: www.centralsemi.com.
6.
Micrel, Inc.: www.micrel.com.
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MIC22700YML Evaluation Board
PCB Layout Recommendations
Top Silk
Top Layer
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MIC22700YML Evaluation Board
PCB Layout Recommendations (Continued)
Bottom Silk
Bottom Layer
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MIC22700YML 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.
© 2008 Micrel, Incorporated.
June 2011
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