MIC23158YML Evaluation Board User Guide

MIC23158/9 Evaluation Board
3MHz, PWM, Dual 2A Buck Regulator with
HyperLight Load® and Power Good
General Description
This board enables the evaluation of the MIC23158, a
fully-integrated 2A, 3MHz, dual switching regulators
®
featuring HyperLight Load mode, power good output
indicator, and programmable soft-start. The MIC23158 is
highly efficient throughout the entire output current range,
drawing just 45µA of quiescent current for both outputs in
®
package, in
operation. The 3mm × 4mm MLF
combination with the 3MHz switching frequency, enables a
compact sub-1mm height solution. The MIC23158
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
This 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) with the
capability to dissipate 7W. It is ideal to have an
oscilloscope available to view the circuit waveforms, but
not essential. For the simplest tests, three voltage meters
are required to measure input and two output voltages. For
efficiency measurements, three voltage meters and three
ammeters are required to prevent errors due to
measurement inaccuracies.
Precautions
There is no reverse input protection on this board,
therefore caution is advised when connecting the input
source to ensure correct polarity is observed.
Evaluating the MIC23159YML
The MIC23159YML provides an auto discharge feature
that switches in a 225Ω pull down circuit on its output to
discharge the output capacitor when disabled. The
evaluation board can be easily modified by interchanging
the MIC23158 device with MIC23159.
Getting Started
1. Connect an external supply to the VIN (J1 or J5)
and GND terminals.
With the output of the power supply disabled, set its
voltage to the desired input test voltage (2.7V ≤ VIN ≤
5.5V). An ammeter may be placed between the input
supply and the VIN (J1 or J5) terminal. Be sure to
monitor the supply voltage at the VIN (J1 or J5)
terminal, as the ammeter and/or power lead resistance
can reduce the voltage supplied to the device..
2. Connect a load to the VOUT (J2 and J6) and GND
terminals.
The load can be either passive (resistive) or active
(electronic load). An ammeter may be placed between
the load and the output terminals. Ensure the output
voltage is monitored at the VOUT (J2 and J6)
terminals.
3. Enable the MIC23158 (J9 and J10).
The MIC23158 evaluation board has a pull-up resistor
to VIN. By default, the output voltage will be enabled
when the input supply of >2.7V is applied. To disable
the device, apply a voltage below 0.4V to the EN
terminals.
4. Power Good (J11 and J12).
A power good test point is provided to monitor the
power good function. The power good output will go
high approximately 70µs after the output voltage
reaches 90% of its nominal voltage.
Ordering Information
Part Number
Description
MIC23158YML EV
Adjustable Output Evaluation Board
(VOUT1 = 1.8V, VOUT2 = 1.5V)
Datasheets and support documentation are available on
Micrel’s web site at: www.micrel.com.
HyperLight Load is a registered trademark of Micrel, Inc.
MLF and MicroLeadFrame are trademarks 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 4, 2013
Revision 1.0
Micrel, Inc.
MIC23158/9 Evaluation Board
Evaluation Board
Some example values are shown in Table 1:
Table 1. Feedback Resistor Values for Adjustable Outputs
VOUT
R4 and R5
R6 and R7
274k
294k
1.5V
316k
221k
1.8V
301k
158k
2.5V
324k
107k
3.3V
309k
71.5k
The feed-forward capacitors (C11 and C12) are typically
not fitted. The transient performance can be improved
slightly by fitting a capacitor at C11 and C12 to inject fast
output voltage deviations directly into the feedback
comparator. This improved load regulation is at the
expense of slightly increasing the amount of noise on the
output at higher loads. Values between 100pF and 1nF are
recommended to prevent instability.
Features
Soft-Start Capacitors (C9 and C10)
The MIC23158 has a nominal 296kΩ resistor charging the
capacitor on the SS pin. This enables the output to follow a
controlled soft start characteristic. Setting C9 and C10 to
470pF sets the startup time to approximately 320µs. The
start-up time can be determined by Equation 1:
3
TSS = 296 × 10 × ln(10) × CSS
Power Good (PG)
The evaluation board has a test point provided for
monitoring the power good feature. This is an open drain
connection with an on-board pull-up resistor of 10k to the
output voltage. Power good is asserted high approximately
70µs after the output voltage passes 90% of the nominal
set voltage.
HyperLight Load Mode
MIC23158 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 over
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 a NMOS
switch instead of a diode allows for lower voltage drop
across the switching device when it is on. The
synchronous 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 MIC23158 works in pulse
frequency modulation (PFM) to regulate the output. As the
output current increases, the off-time decreases, thus
providing more energy to the output. This switching
scheme improves the efficiency of MIC23158 during light
load currents by only switching when it is needed.
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 (R4, R5, R6, and R7) for
Adjustable Outputs
The output voltages are set nominally to 1.8V and 1.5V.
These outputs can be changed by adjusting the upper
resistor, R4 and R5, in the feedback potential divider.
Therefore:
R4 = R6 x (VO−VREF)/VREF
R5 = R7 x (VO−VREF)/VREF
where VREF = 0.62V.
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1.2V
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Micrel, Inc.
MIC23158/9 Evaluation Board
As the load current increases, the MIC23158 goes into
continuous conduction mode (CCM) and switches at a
frequency centered at 3MHz. The equation to calculate the
load when the MIC23158 goes into continuous conduction
mode may be approximated by Equation 2:
ILOAD >
 (VIN − VOUT ) × D 


2L × f


Eq. 2
As shown in Equation 2, the load at which MIC23158
transitions from HyperLight Load mode to PWM mode is a
function of the input voltage (VIN), output voltage (VOUT),
duty cycle (D), inductance (L) and frequency (f). Refer to
the “Switching Frequency vs. Output Current” graph in the
Evaluation Board Performance section to see an example
of how when the output current increases, the switching
frequency also increases until the MIC23158 goes from
HyperLight Load mode to PWM mode at approximately
180mA. The MIC23158 will switch at a relatively constant
frequency around 3MHz once the output current is over
180mA.
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Micrel, Inc.
MIC23158/9 Evaluation Board
Evaluation Board Performance
100
90
90
80
80
VIN = 4.2V
70
VIN = 5V
EFFICIENCY (%)
60
50
40
30
20
90
80
70
VIN = 4.2V
VIN = 3.6V
VIN = 5V
60
50
40
30
COUT=4.7µF
L=1µH
COUT=4.7µF
L=1µH
10
0
10
100
1000
10000
10
100
1000
RISE TIME (µs)
EFFICIENCY (%)
VIN = 2.7V
VIN = 5V
VIN = 4.2V
40
COUT=4.7µF
L=1µH
10
0
1
10
100
1000
OUTPUT CURRENT (mA)
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10000
100
1000
10000
5.0
10000
1000
100
10
100
10
Switching Frequency
vs. Output Current
30
20
COUT=4.7µF
L=1µH
1
1000000
VIN = 3.6V
50
30
OUTPUT CURRENT (mA)
100000
60
40
10000
90
70
50
VOUT Rise Time
vs. CSS
80
VIN = 5V
VIN = 4.2V
OUTPUT CURRENT (mA)
Efficiency (VOUT = 1.5V) vs.
Output Current
VIN = 3.6V
0
1
OUTPUT CURRENT (mA)
100
VIN = 2.7V
60
10
0
1
70
20
20
10
Efficiency (VOUT = 1.8V) vs.
Output Current
100
VOUT = 1.8V
COUT = 4.7µF
SWITCHING FREQUENCY (MHz)
EFFICIENCY (%)
100
Efficiency (VOUT = 2.5V) vs.
Output Current
EFFICIENCY (%)
Efficiency (VOUT = 3.3V) vs.
Output Current
4.5
4.0
L=1.0µH
3.5
3.0
L=0.47µH
2.5
2.0
1.5
1.0
0.5
0.0
1000
10000
CSS (pF)
4
100000
1000000
0.1
1
10
100
1000
10000
OUTPUT CURRENT (mA)
Revision 1.0
Micrel, Inc.
MIC23158/9 Evaluation Board
Evaluation Board Schematic (Adjustable Output)
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Micrel, Inc.
MIC23158/9 Evaluation Board
Bill of Materials
Item
Part Name
06036D475KAT2A
C1, C2,
C7, C8
C3, C4
C9, C10
C13
L1, L2
R1, R2,
R3, R12
R4
R5
R6
R7
R8, R9
R10, R11
U1
GRM188R60J475KE19D
Manufacturer
(2)
TDK
AVX
Murata
TDK
AVX
Murata
TDK
LQH44PN1R0NJ0
CRCW06030000Z0EA
CRCW06033013FKEA
CRCW06033163FKEA
CRCW06031583FKEA
CRCW06032213FKEA
CRCW06031003FKEA
CRCW06031002FKEA
MIC23158YML
4.7µF, 6.3V, X5R, 0603
4
1µF, 0603, 6.3V
2
470pF, 50V, 0603
2
Cap Alum, 100µF, 50V, 20%, Radial
1
(3)
06036D105KAT2A
GRM188R60J105KA01D
C1608X5R0J105K
06035A471JAT2A
GRM1885C1H471JA01D
C1608C0G1H471J
CDRH4D28CLDNP-1R0P
Qty.
AVX
Murata
C1608X5R0J475K
EKY-500ELL101MHB5D
Description
(1)
United Chemi-con
Sumida
(4)
1µH, 3.0A, 14mΩ, L5.1mm × W5.1mm × H3.0mm
(5)
Murata
Vishay/Dale
(6)
Vishay/Dale
Vishay/Dale
Vishay/Dale
Vishay/Dale
Vishay/Dale
Vishay/Dale
(7)
Micrel, Inc.
1µH, 2.0A, 48mΩ, L4.0mm × W4.0mm × H1.1mm
2
0Ω, 1/10W, 0603
4
301KΩ, 1%, 1/10W, 0603
316KΩ, 1%, 1/10W, 0603
158KΩ, 1%, 1/10W, 0603
221KΩ, 1%, 1/10W, 0603
100KΩ, 1%, 1/10W, 0603
10KΩ, 1%, 1/10W, 0603
3MHz, PWM, Dual 2A Buck Regulator with
HyperLight Load and Power Good
1
1
1
1
2
2
1
Notes:
1.
AVX: www.avx.com.
2.
Murata: www.murata.com.
3.
TDK: www.tdk.com.
4.
United Chemi-con: www.chemi-con.com.
5.
Sumida: www.sumida.com.
6.
Vishay: www.vishay.com.
7.
Micrel, Inc.: www.micrel.com.
February 4, 2013
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Revision 1.0
Micrel, Inc.
MIC23158/9 Evaluation Board
PCB Layout Recommendations
Top Layer
Bottom Layer
February 4, 2013
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Revision 1.0
Micrel, Inc.
MIC23158/9 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.
© 2013 Micrel, Incorporated.
February 4, 2013
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Revision 1.0
Micrel, Inc.
MIC23158/9 Evaluation Board
Revision History
Date
Change Description/Edits by:
02/04/13
Initial draft version reflowed into 2013 template – by S. Thompson
February 4, 2013
Rev.
9
1.0
Revision 1.0