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 V
IN
(J4)
terminal and GND (J3).
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
(J4) terminal. Be sure to
monitor the supply voltage at the V
IN
(J4)
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
(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 V
OUT
(J1) terminal.
3.
Enable the MIC23153.
The MIC23153
evaluation board has a pull-up resistor to V
IN
. 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
MIC23153-GYMT
MIC23153YMT
Description
1.8V Fixed Output Evaluation Board
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.
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 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 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:
⎛
(V
−
V
OUT
)
×
D
⎞
⎟
I
LOAD
> ⎜
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 (V
IN
), output
voltage (V
OUT
), 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.
Evaluation Board
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:
T
SS
= 270 x 10
3
x ln(10) x C
SS
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 V
REF
/(V
O
-V
REF
)
Where V
REF
= 0.62V
Some example values are:
V
OUT
1.2V
1.5V
1.8V
2.5V
3.3V
R1
274k
316k
301k
324k
309k
R2
294k
221k
158k
107k
71.5k
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
February 2010
2
M9999-020510-A
Micrel, Inc.
MIC23153 Evaluation Board
Evaluation Board Performance
Switching Frequency
v s. Load Current
10000
1000
100
10
1
0.1
0.00001
V
IN
= 3V
100%
Efficiency v s. Output Current
V
OUT
= 1.8V @ 25°C
V
IN
= 3V
Efficiency v s. Output Current
V
OUT
= 3.3V @ 25°C
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
0.00001
V
IN
= 5.5V
V
IN
= 4.2V
90%
SW FREQUENCY (kHz)
80%
EFFICIENCY (%)
V
IN
= 5V
V
IN
= 5V
V
IN
= 3.6V
V
IN
= 3.6V
60%
50%
40%
30%
20%
0.001
0.1
LOAD CURRENT (A)
10
10%
0.00001
0.001
0.1
OUT PUT CURRENT (A)
10
EFFICIENCY (%)
70%
V
IN
= 5V
0.001
0.1
OUT PUT CURRENT (A)
10
1000000
100000
V
OUT
Rise Tim e
v s. C
SS
Enable Threshold
v s. Input Voltage
1.2
1.1
VEN THRESHOLD (V)
1.0
0.9
0.8
0.7
0.6
0.5
RISE TIM E (µs)
10000
1000
100
10
1
100
1000
10000
100000 1000000
CSS (pF)
2.5
3.0
3.5
4.0
4.5
INPUT VOLT AGE (V)
5.0
5.5
February 2010
3
M9999-020510-A
Micrel, Inc.
MIC23153 Evaluation Board
MIC23153-xYMT Evaluation Board Schematic (Fixed Output)
Bill of Materials
Item
Part Number
Manufacturer
Description
Qty.
C1
C2
C3
C4
L1
R1
R2
R3
R4
U1
Notes:
C1608X5R0J475K
GRM188R60J475KE19D
C1608X5R0J475K
GRM188R60J475KE84D
C1608NPO0J471K
-
VLS3012ST-1R0N1R9
LQH44PN1R0NJ0
-
-
CRCW06031002FKEA
CRCW06031002FKEA
MIC23153-xYMT
TDK
Murata
(2)
TDK
Murata
TDK
-
TDK
Murata
-
-
Vishay
(3)
Vishay
Micrel, Inc.
(4)
(1)
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
Not Fitted (NF)
Not Fitted (NF)
Resistor,10k, Size 0603
Resistor,10k, Size 0603
4MHz 2A Buck Regulator with HyperLight Load™ Mode
1
0
1
0
0
1
1
1
1. TDK:
www.tdk.com.
2. Murata:
www.murata.com.
3. Vishay:
www.vishay.com.
4.
Micrel, Inc.:
www.micrel.com.
February 2010
4
M9999-020510-A
Micrel, Inc.
MIC23153 Evaluation Board
MIC23153 Evaluation Board Schematic (Adjustable Output)
Bill of Materials
Item
Part Number
Manufacturer
Description
Qty.
C1
C2
C3
C4
L1
R1
R2
R3
R4
U1
Notes:
C1608X5R0J475K
GRM188R60J475KE19D
C1608X5R0J475K
GRM188R60J475KE84D
C1608NPO0J471K
-
VLS3010ST-1R0N1R9
LQH44PN1R0NJ0
CRCW06033013FKEA
CRCW06031583FKEA
CRCW06031002FKEA
CRCW06031002FKEA
MIC23153YMT
TDK
Murata
(2)
TDK
Murata
TDK
-
TDK
Murata
(2)
Vishay
(3)
Vishay
Vishay
Vishay
Micrel, Inc.
(4)
(1)
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
Resistor,301k, Size 0603
Resistor,158k, Size 0603
Resistor,10k, Size 0603
Resistor,10k, Size 0603
4MHz 2A Buck Regulator with HyperLight Load™ Mode
1
0
1
1
1
1
1
1
1. TDK:
www.tdk.com.
2. Murata:
www.murata.com.
3. Vishay:
www.vishay.com.
4.
Micrel, Inc.:
www.micrel.com.
February 2010
5
M9999-020510-A
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