MIC23153-GYMT Evaluation Board User Guide

MIC23153 Evaluation Board
4MHz PWM 2A Buck Regulator with
HyperLight Load™ and Power Good
General Description
This board enables the evaluation of the MIC23153, a
fully integrated 2A, 4MHz switching regulator featuring
HyperLight Load™ mode, Power Good output indicator,
and programmable soft-start. The MIC23153 is highly
efficient throughout the entire output current range,
drawing just 23µA of quiescent current in operation. The
tiny 2.5mm x 2.5mm Thin MLF® package, in combination
with the 4MHz switching frequency, enables a compact
sub-1mm height solution with only four external
components. The MIC23153 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 needs a single 10W 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, two Voltage meters
are required to measure input and output voltage. For
efficiency measurements, two Voltage meters and two
Ammeters are required to prevent errors due to
measurement inaccuracies.
Precautions
There is no reverse input protection on this board. Be
cautious when connecting the input source to ensure
correct polarity is observed.
Getting Started
1. Connect an external supply to the VIN (J4)
terminal and GND (J3). 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 (J4) terminal. Be sure to
monitor the supply voltage at the VIN (J4)
terminal, as the ammeter and/or power lead
resistance can reduce the voltage supplied to
the device.
2. Connect a load to the VOUT (J1) and ground
(J2) terminals. The load can be either active
passive (resistive) or active (electronic load). An
ammeter may be placed between the load and
the output terminal. Ensure the output voltage is
monitored at the VOUT (J1) terminal.
3. Enable the MIC23153. The MIC23153
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 0.5V to the EN
(J6) terminal.
4. Power Good. A Power good test point (J5) is
provided to monitor the Power Good function.
The Power Good output will go high (Vout)
approximately 70µs after the output voltage
reaches 92% of its nominal voltage.
Ordering Information
Part Number
Description
MIC23153-GYMT
1.8V Fixed Output Evaluation Board
MIC23153YMT
Adjustable Output Evaluation Board
HyperLight Load is a trademark of Micrel, Inc.
MLF and MicroLeadFrame are registered trademark 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 2010
M9999-020510-A
Micrel, Inc.
MIC23153 Evaluation Board
at C4 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.
Evaluation Board
Power Good (PG)
The evaluation board has a test point provided to the
right of EN for testing PG. This is an open drain
connection with an on board pull-up resistor of 10k to the
output voltage. This is asserted high approximately 70μs
after the output voltage passes 92% of the nominal set
voltage.
HyperLight Load™ Mode
MIC23153 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 minimumoff-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 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 MIC23153 works
in pulse frequency modulation (PFM) to regulate the
output. As the output current increases, the off-time
decreases, thus provides more energy to the output.
This switching scheme improves the efficiency of
MIC23153 during light load currents by only switching
when it is needed. As the load current increases, the
MIC23153 goes into continuous conduction mode (CCM)
and switches at a frequency centered at 4MHz. The
equation to calculate the load when the MIC23153 goes
into continuous conduction mode may be approximated
by the following formula:
Other Features
Soft-Start Capacitor (C3)
The MIC23153 has a nominal 270kOhm resistor
charging the capacitor on the SS pin. This enables the
output to follow a controlled soft start characteristic.
Setting C3 to 100pF sets the startup time to the
minimum. The start-up time can be determined by:
TSS = 270 x 103 x ln(10) x CSS
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) for Adjustable Output
The output voltage is set nominally to 1.8V. This output
can be changed by adjusting the upper resistor, R1, in
the feedback potential divider. Therefore:
R1 = R2 x VREF/(VO-VREF)
Where VREF = 0.62V
Some example values are:
VOUT
R1
R2
1.2V
274k
294k
1.5V
316k
221k
1.8V
301k
158k
2.5V
324k
107k
3.3V
309k
71.5k
⎛ (V − VOUT ) × D ⎞
⎟⎟
ILOAD > ⎜⎜ IN
2L × f
⎝
⎠
As shown in the previous equation, the load at which
MIC23153 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). As shown in the Switching Frequency vs
Load graph, as the Output Current increases, the
switching frequency also increases until the MIC23153
goes from HyperLight Load™ mode to PWM mode at
approximately 120mA. The MIC23153 will switch at a
relatively constant frequency around 4MHz once the
output current is over 120mA.
The Feed-forward capacitor, C4, is typically not fitted
since transient load regulation is already very good,
however, it can be improved slightly by fitting a capacitor
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Micrel, Inc.
MIC23153 Evaluation Board
Evaluation Board Performance
Efficiency v s. Output Current
VOUT = 1.8V @ 25°C
Switching Frequency
v s. Load Current
100%
1000
100
VIN = 3.6V
VIN = 5V
10
1
0.1
0.00001
0.001
0.1
LOAD CURRENT (A)
80%
70%
VIN = 5V
60%
VIN = 3.6V
50%
40%
70%
60%
50%
40%
30%
30%
20%
20%
10%
0.001
0.1
OUT PUT CURRENT (A)
10
VIN = 5V
VIN = 5.5V
0%
0.00001
0.001
0.1
OUT PUT CURRENT (A)
10
1.2
1.1
VEN THRESHOLD (V)
100000
RISE TIM E (µs)
80%
VIN = 4.2V
Enable Threshold
v s. Input Voltage
VOUT Rise Tim e
v s. C SS
1000000
90%
10%
0.00001
10
100%
VIN = 3V
90%
EFFICIENCY (%)
VIN = 3V
EFFICIENCY (%)
SW FREQUENCY (kHz)
10000
Efficiency v s. Output Current
VOUT = 3.3V @ 25°C
10000
1000
100
10
1.0
0.9
0.8
0.7
0.6
1
0.5
100
1000
February 2010
10000
100000 1000000
CSS (pF)
2.5
3.0
3.5
4.0
4.5
INPUT VOLT AGE (V)
3
5.0
5.5
M9999-020510-A
Micrel, Inc.
MIC23153 Evaluation Board
MIC23153-xYMT Evaluation Board Schematic (Fixed Output)
Bill of Materials
Item
C1
C2
C3
C4
L1
Part Number
C1608X5R0J475K
GRM188R60J475KE19D
C1608X5R0J475K
GRM188R60J475KE84D
C1608NPO0J471K
VLS3012ST-1R0N1R9
LQH44PN1R0NJ0
Manufacturer
TDK(1)
Murata(2)
TDK
Murata
TDK
TDK
Murata
R1
-
-
R2
-
-
R3
CRCW06031002FKEA
R4
CRCW06031002FKEA
U1
MIC23153-xYMT
(3)
Vishay
Vishay
Micrel, Inc.(4)
Description
Qty.
1
Ceramic Capacitor, 4.7µF, 6.3V, X5R, Size 0603
1
Ceramic Capacitor, 470pF, 6.3V, NPO, Size 0603
Not Fitted (NF)
1µH, 2A, 60mΩ, L3.0mm x W3.0mm x H1.0mm
1µH, 2.8A, 50mΩ, L4.0mm x W4.0mm x H1.2mm
1
0
Not Fitted (NF)
0
Not Fitted (NF)
0
Resistor,10k, Size 0603
1
Resistor,10k, Size 0603
1
4MHz 2A Buck Regulator with HyperLight Load™ Mode
1
1
Notes:
1. TDK: www.tdk.com.
2. Murata: www.murata.com.
3. Vishay: www.vishay.com.
4. Micrel, Inc.: www.micrel.com.
February 2010
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M9999-020510-A
Micrel, Inc.
MIC23153 Evaluation Board
MIC23153 Evaluation Board Schematic (Adjustable Output)
Bill of Materials
Item
C1
C2
C3
C4
L1
Part Number
C1608X5R0J475K
GRM188R60J475KE19D
C1608X5R0J475K
GRM188R60J475KE84D
C1608NPO0J471K
VLS3010ST-1R0N1R9
LQH44PN1R0NJ0
Manufacturer
TDK(1)
Murata(2)
TDK
Murata
TDK
TDK
Murata(2)
(3)
Vishay
Description
Qty.
1
Ceramic Capacitor, 4.7µF, 6.3V, X5R, Size 0603
1
Ceramic Capacitor, 470pF, 6.3V, NPO, Size 0603
Not Fitted (FT)
1µH, 2A, 60mΩ, L3.0mm x W3.0mm x H1.0mm
1µH, 2.8A, 50mΩ, L4.0mm x W4.0mm x H1.2mm
1
0
1
R1
CRCW06033013FKEA
Resistor,301k, Size 0603
1
R2
CRCW06031583FKEA
Vishay
Resistor,158k, Size 0603
1
R3
CRCW06031002FKEA
Vishay
Resistor,10k, Size 0603
1
R4
CRCW06031002FKEA
Resistor,10k, Size 0603
1
U1
MIC23153YMT
4MHz 2A Buck Regulator with HyperLight Load™ Mode
1
Vishay
Micrel, Inc.(4)
Notes:
1. TDK: www.tdk.com.
2. Murata: www.murata.com.
3. Vishay: www.vishay.com.
4. Micrel, Inc.: www.micrel.com.
February 2010
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M9999-020510-A
Micrel, Inc.
MIC23153 Evaluation Board
PCB Layout Recommendations
Thin MLF Top Layer
Thin MLF Bottom Layer
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.
© 2010 Micrel, Incorporated.
February 2010
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