MIC23163/4
4MHz, 2A, 100% Duty Cycle Buck Regulator
with HyperLight Load® and Power Good
HyperLight Load is a registered t radem ark of Micrel, Inc.
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • US A • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
June
29, 2013
Revision 2.0
General Description
The MIC23163/4 is a high-efficiency, 4MHz, 2A,
synchronous buck regulator with HyperLight Load® (HLL)
mode and maximum 100% duty cycle. HLL provides very-
high efficiency at light loads and ultra-fast transient
response w hich makes the MIC 23 16 3/4 per f ect ly su ite d f or
suppl ying process or core volta ges. An a dditional b enefit of
this proprietary architecture is very low output ripple
voltage throughout the entire load range with the use of
small output capacitors. The tiny 2.0mm × 2.0mm DFN
package saves precious board space and requires only
three external components.
The MIC23163/4 is designed for use with a very small
0.47µH inductor and 10µF output capacitor that enables a
total solution size, less than 1mm height.
The MIC231 63/4 has a v ery low quiesc ent current of 33µA
and achieves as high as 85% efficienc y at 1m A. At higher
loads, the MIC23163/4 provides a constant switching
frequency around 4MHz while achieving peak efficiencies
up to 93%. The MIC23164 incorporates an active
discharge f eature that s witches an 180Ω F ET to grou nd to
discharge the output when the part is disabled.
The MIC23163/4 is available in 10-pin 2.0mm × 2.0mm
DFN package with an operating junction temperature
range from –40°C to +125°C.
Datasheets and support documentation are available on
Micrel’s web site at: www.micrel.com.
Features
• Input voltage: 2.7V to 5.5V
• 100% duty cycle
• 2A output current
• Up to 93% peak efficiency
• 85% typical efficiency at 1mA
• Programmable soft-start with pre-bias start-up capability
• Power Good (PG) Indicator
• 4MHz PWM operation in continuous mode
• Ultra-fast transient response
• Low ripple output voltage
• Fully-integrated MOSFET switches
• 0.1µA shutdown current
• Thermal shutdown and current-limit protection
• 10-pin 2.0mm × 2.0mm Thin DFN
• –40°C to +125°C junction temperature range
• Disable pull down 180Ω (MIC23164 only)
Applications
• Cellular modems
• Mobile handsets
• Portable media/MP3 players
• Portable navigation devices (GPS)
• WiFi/WiMax/WiBro modules
• Digital cameras
• Wireless LAN cards
Typical Applic ation
Micrel, Inc.
MIC23163/4
Jul y 2
9, 2013 2 Revision 2.0
Ordering Information
Part Number Marking
Code Output
Voltage Auto
Discharge Junction Temperature Range Package(1, 2)
MIC23163YMT QAQ ADJ No –40°C to +125°C 10-Pin 2mm × 2mm Thin DFN
MIC23164YMT KQA ADJ Yes –40°C to +125°C 10-Pin 2m m × 2mm Thin DFN
Note:
1. DFN is a GRE EN, RoHS-compliant package. Mold compound is Halogen Free.
2. DFN ▲ = Pin 1 identifier.
Pin Configuration
2mm × 2mm DFN (MT)
Adjustable Output Voltage
(Top View)
Pin Description
Pin Number Pin Name Pin Function
1 SW Switch (Output): Internal power MOSFET output switches. Disable pull down 180Ω
(MIC23164 only).
2 EN Enable (Input): Logic high enables operation of the regulator. Logic low will shut down the
device. Do not leave floating.
3 FB Feedbac k: Connec t a resistor div ider from the out p ut to ground to set the outp ut volt age.
4 NC Not Internally Connected.
5 PG Power Good: Open drain output for the power good indicator. Use a pull-up resistor from this pin
to a voltage source to detect a power good condition.
6 SS Soft Start: Place a capacitor from this pin to ground to program the soft start time. Do not leave
floating, 100pF minimum CSS is required.
7 AGND Analog Ground: Connect to central ground point where all high-current paths meet (CIN, COUT,
PGND) for best operation.
8 AVIN Analog Input Voltage: Connect a capacitor to ground to decouple the noise.
9 PVIN Power Input Voltage: Connect a capacitor to PGND to decouple the noise.
10 PGND Power Ground.
EP ePad Exposed Pad. Connect to GND.
Micrel, Inc.
MIC23163/4
Jul y 2
9, 2013 3 Revision 2.0
Absolute Maximum Ratings(3)
Supply Voltage (VAVIN, VPVIN) ............................. −0.3V to 6V
Power Good Voltage (VPG) ................................ −0.3V to 6V
Output Switc h Voltage (VSW) ............................. −0.3V to 6V
Enable Input Voltage (VEN) .. ..............................−0.3V to VIN
Junction Temperature (TJ) ....................................... +150°C
Storage Temperature Range (TS) ............. −65°C to +150°C
Lead Temperature (soldering, 10s) ............................ 260°C
ESD Rating(5) ................................................. ESD Sensitive
Operating Ratings(4)
Supply Voltage (VAVIN, VPVIN) ............................ 2.7V to 5.5V
Enable Input Voltage (VEN) .. ……………………….0V to VIN
Feedback Voltage (VFB) ...................................... 0.7V to VIN
Junction Temperature Range (TJ) .. ….−40°C ≤ TJ ≤ +125°C
Thermal Resistance
2mm x 2mm Thin DFN -10 (θJA) ......................... 90°C/W
2mm x 2mm Thin DFN -10 (θJC) ......................... 45°C/W
Electrical Characteristics(6)
TA = 25°C; VIN = VEN = 3.6V; L = 0.47µH; COUT = 10µF unless otherwise specified. Bold values indicate –40°C ≤ TJ ≤ +125°C, unless
otherwise noted.
Parameter Condition Min. Typ. Max. Units
Supply Voltage Range 2.7 5.5 V
Undervoltage Lockout Threshold (Turn-On) 2.40 2.53 2.65 V
Undervoltage Lockout Hysteresis 75 mV
Quiescent Current IOUT = 0mA , VSNS > 1.2 × VOUT Nominal 33 55 µA
Shutdown Current VEN = 0V; VIN = 5.5V 0.1 5 µA
Output Voltage Accuracy VIN = 3.6V if VOUTNOM < 2.5V, ILOAD = 20m A
−
2.5 +2.5 %
VIN = 4.5V if VOUTNOM ≥ 2.5V, ILOAD = 20mA
Feedback Regulation Voltage 0.68 0.7 0.72 V
Current Limit VSNS = 0.9*VOUTNOM 2.5 3.3 A
Output Voltage Line Regulation VIN = 3.6V to 5.5V if VOUTNOM < 2.5V, ILOAD = 20mA 0.3 %/V
VIN = 4.5V to 5.5V if VOUTNOM ≥ 2.5V, ILOAD = 20mA
Output Voltage Load Regulation
20mA < ILOAD < 500mA, VIN = 3.6V if VOUTNOM < 2.5V 0.3
%
20mA < ILOAD < 500mA, VIN = 5.0V if VOUTNOM ≥ 2.5V
20mA < ILOAD < 1A, VIN = 3.6V if VOUTNOM < 2.5V 0.3
20mA < ILOAD < 1A, VIN = 5.0V if VOUTNOM ≥ 2.5V
PWM Switch ON-Resistance ISW = 100mA PMOS 0.13
0.13 Ω
ISW = −100mA NMOS
Switching Frequency IOUT = 120mA 4 MHz
Soft-Start Time VOUT = 90%, CSS = 1nF 1000 µs
Soft-Start Current VSS = 0V 2.2 µA
Power Good Threshold (Rising) % of VNOM 85 90 95 %
Notes:
3. Exceeding the absolute maximum ratings may damage the device.
4. The device is not guarant eed to function outside its operat i ng ratings.
5. Devices are ESD sensitive. Handling precautions are recommended. Human body model, 1.5kΩ in series with 100pF.
6. Specific at i on for pack aged product only.
Micrel, Inc.
MIC23163/4
Jul y 2
9, 2013 4 Revision 2.0
Electrical Characteristics(6) (Continued)
TA = 25°C; VIN = VEN = 3.6V; L = 0.47µH; COUT = 10µF unless otherwise specified. Bold values indicate –40°C ≤ TJ ≤ +125°C, unless
otherwise noted.
Parameter Condition Min. Typ. Max. Units
Power Good Threshold Hysteresis 7 %
Power Good Pull-Down VSNS = 90% VNOMINAL, IPG = 1mA 200 mV
Enable Threshold Turn-On 0.5 0.8 1.2 V
Enable Input Current 0.1 2 µA
Overtemperature Shutdown 160 °C
Overtemperature Shutdown
Hysteresis 20 °C
SW Pull-Down Resistance
(MIC23164 only) VEN = 0V 180 Ω
Micrel, Inc.
MIC23163/4
Jul y 2
9, 2013 5 Revision 2.0
Typical Characteris tics
50
55
60
65
70
75
80
85
90
95
110 100 1000 10000
EFFICIENCY (%)
OUTPUT CURRENT (mA)
Efficie nc y vs. Output Cur rent
V
OUT
= 1.8V @ 25°C
VIN = 3V
VIN = 3.6V VIN = 5V
50
55
60
65
70
75
80
85
90
95
100
110 100 1000 10000
EFFICIENCY (%)
OUTPUT CURRENT (mA)
Efficie nc y vs. Output Cur rent
V
OUT
= 3.3V @ 25°C
VIN = 5V
VIN = 4.2V
1
10
100
1000
10000
100000
1000000
1000 10000 100000 1000000
RISE TIME (µs)
C
SS
(pF)
V
OUT
Rise Time vs. C
SS
V
IN = 3.6V
2.6
2.8
3
3.2
3.4
3.6
3.8
2.5 3.0 3.5 4.0 4.5 5.0 5.5
CURRENT LIMIT (A)
INPUT VOLTAGE (V)
Current Limit v s.
Input Voltage
TCASE = 25°C
20
25
30
35
40
45
50
2.5 3.0 3.5 4.0 4.5 5.0 5.5
IQ (µA)
INPUT VOLTAGE (V)
Quiscent Current vs.
Input Voltage
T
CASE
= 25°C
30
32
34
36
38
40
42
44
46
48
50
-40 -20 020 40 60 80 100 120
IQ (µA)
TEMPERATURE (°C)
IQ vs. Temperature
V
IN
= 3.6V
1.854
1.855
1.856
1.857
1.858
1.859
1.860
1.861
1.862
1.863
1.864
2.5 3.0 3.5 4.0 4.5 5.0 5.5
OUTPUT VOLTAGE (V)
INPUT VOLTAGE (V)
Line Regulation
(Light Loads)
IOUT = 130mA
IOUT = 30mA
1.850
1.852
1.854
1.856
1.858
1.860
1.862
1.864
1.866
1.868
1.870
2.5 3.0 3.5 4.0 4.5 5.0 5.5
OUTPUT VOLTAGE (V)
INPUT VOLTAGE (V)
Line Regulation
(High Loads)
IOUT = 300mA
I
OUT
= 1A
1.790
1.795
1.800
1.805
1.810
1.815
1.820
020 40 60 80 100 120 140 160 180 200
OUTPUT VOLTAGE (V)
OUTPUT CURRENT (mA)
Output Voltage vs.
Output Current (DCM)
V
IN
= 3.6V
Micrel, Inc.
MIC23163/4
Jul y 2
9, 2013 6 Revision 2.0
Typical Characteristics (Continued)
1.780
1.785
1.790
1.795
1.800
1.805
1.810
1.815
1.820
200 500 800 1100 1400 1700 2000
OUTPUT VOLTAGE (V)
OUPUT CURRENT (mA)
Output Voltage vs.
Output Current (CCM)
VIN = 3.6V
1.900
1.920
1.940
1.960
1.980
2.000
2.020
2.040
2.060
2.080
2.100
-40 -20 020 40 60 80 100 120
OUTPUT VOLTAGE (V)
TEMPERATURE (°C)
Output Voltage vs.
Temperature
V
IN
= 3.6V
I
OUT
= 30mA
82
83
84
85
86
87
88
89
90
91
92
2.5 3.0 3.5 4.0 4.5 5.0 5.5
PG THRESHOLD (% OF V
REF
)
INPUT VOLTAGE (V)
PG Thresholds vs.
Input Voltage
PG RISING
PG FALLING
10
15
20
25
30
35
40
2.5 3.0 3.5 4.0 4.5 5.0 5.5
PG DELAY TIME (µS)
INPUT VOLTAGE (V)
PG Delay Time
vs. Input Voltage
PG RISING
PG FALLING
2.46
2.48
2.5
2.52
2.54
2.56
2.58
-40 -20 020 40 60 80 100 120
UVLO THRESHOLDS (V)
TEMPERATURE (°C)
UVLO Thresholds vs.
Temperature
UVLO ON
UVLO OFF
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
2.5 3.0 3.5 4.0 4.5 5.0 5.5
ENABLE THRESHOLD (V)
INPUT VOLTAGE (V)
Enable Thresholds
vs. Input Voltage
TCASE = 25°C
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
-40 -20 020 40 60 80 100 120
ENABLE THRESHOLDS (V)
TEMPERATURE (°C)
Enable Threshold vs.
Temperature
V
IN
= 3.6V
1
10
100
1000
10000
110 100 1000 10000
SW FREQUENCY (kHz)
OUPUT CURRENT (mA)
Switching Frequency vs.
Output Curre nt
VIN = 5V
VIN = 3.6V
0.680
0.685
0.690
0.695
0.700
0.705
0.710
0.715
0.720
-40 -20 020 40 60 80 100 120
FEEDBACK VOLTAGE (V)
TEMPERATURE (°C)
Feedback Voltage vs.
Temperature
Micrel, Inc.
MIC23163/4
Jul y 2
9, 2013 7 Revision 2.0
Typical Characteristics (Continued)
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.10
-40 -20 020 40 60 80 100 120
SHUTDOWN CURRENT (µA)
TEMPERATURE (°C)
Shutdown Current vs.
Temperature
Micrel, Inc.
MIC23163/4
Jul y 2
9, 2013 8 Revision 2.0
Functional Characteristics
Micrel, Inc.
MIC23163/4
Jul y 2
9, 2013 9 Revision 2.0
Functional Characteristics (Continued)
Micrel, Inc.
MIC23163/4
Jul y 2
9, 2013 10 Revision 2.0
Functional Characteristics (Continued)
Micrel, Inc.
MIC23163/4
Jul y 2
9, 2013 11 Revision 2.0
Functional Diagram
Figure 1. Simplified MIC23163/4 Functional Block Diagram
−
Adjustable Output Voltage
Micrel, Inc.
MIC23163/4
Jul y 2
9, 2013 12 Revision 2.0
Functional Description
VIN
The input supply (VIN) provides power to the internal
MOSFETs for the switch-mode regulator along with the
internal control circuitr y. The VIN operating range is 2.7V
to 5.5V so an input capacitor, with a minimum voltage
rating of 6.3V, is recommended. Due to the high
switching speed, a minimum 2.2µF bypass capacitor
placed clos e to VIN an d the power gro und (PGND) p in is
required. Refer to the “PCB Layout Recommendations”
section for details.
EN/Shutdown
A logic high signal on the enable pin activates the output
voltage of the device. A log ic low sig nal on th e enabl e pin
deactivates the output and reduces supply current to
0.1µA. W hen disab led the MIC2316 4 switc hes an internal
load of 180Ω on the regulators switch node to discharge
the output. The MIC23163/4 features external soft-start
circuitry via the soft start (SS) pin that reduces in-rush
current and prevents the output voltage from
overshooting at start up. Do not leave the EN pin floating.
SW
The switch (SW) connects directly to one end of the
inductor and provides the current path during switching
cycles. The other end of the inductor is connected to the
load, SNS pin and output capacitor. Due to the high-
speed switching on this pin, the switch node should be
routed away from sensitive nodes whenever possible.
AGND
The analog ground (AGND) is the ground path for the
biasing and control circuitry. The current loop for the
signal ground should be separate from the power ground
(PGND) loop. Refer to the “PCB Layout
Recommendations” section for details.
PGND
The power ground pin is the ground path for the high
current in PWM mode. The current loop for the power
ground s hould be as sm all as possib le and s eparat e f rom
the analog ground (AGND) loop as applicable. Refer to
the “PCB Layout Recommendations” section for details.
PG
The power good (PG) pin is an open drain output which
indicates logic high when the output voltage is typically
above 90% of its steady state voltage. A pull-up resistor
of more than 5kΩ should be connected from PG to VOUT.
SS
The soft start (SS) pin is used to control the output
voltage ramp up time. The approximate equation for the
ramp time in seconds is 270 × 103 × ln(10) × CSS. For
example, for a CSS = 1nF, TRISE ~ 600µs. The minimum
recommended value for CSS is 1nF.
FB
The feedback (FB) pin is provided for the adjustable
voltage option (no internal connection for fixed options).
This is the control input for programming the output
voltage. A res is tor d i vid er n et work is connected t o t his pin
from the output and is compared to the internal 0.7V
reference within the regulation loop.
The output voltage can be programmed between 0.7V
and VIN using Equation 1:
+×= R2
R1
1VV REFOUT
Eq. 1
where:
R1 is the top resistor, R2 is the bottom resistor.
Table 1. Example Feedback Resistor Values
VOUT R1 R2
1.2V 215k 301k
1.5V 301k 261k
1.8V 340k 215k
2.5V 274k 107k
3.3V 383k 102k
3.6V 422k 102k
Micrel, Inc.
MIC23163/4
Jul y 2
9, 2013 13 Revision 2.0
Application Information
The MIC23163/4 is a high-performance DC/DC step-
down regulator offering a small solution size. Supporting
an output cur rent up to 2A i nside a t in y 2mm × 2mm DFN
package, the IC requires onl y three external components
while meeting today’s miniature portable electronic
device needs . U si ng t he HyperLight Lo ad (HLL) switching
scheme, the MIC23163/4 is able to maintain high
efficiency throughout the entire load range while
providing ultra-f ast load tr ansient r esponse. The f ollowing
sections provide additional device application information.
Input Capacitor
A 2.2µF ceramic capacitor or greater should be placed
close to the VIN pin and PGND pin for bypassing. A
Murata GRM188R60J475ME84D, size 0603, 4.7µF
ceramic capacitor is recommended based on
performance, size, and cost. A X5R or X7R temperature
rating is recommended for the input capacitor. Y5V
temperature rating capacitors, aside from losing most of
their capacitance over temperature, can also become
resistive at high frequencies. This reduces their ability to
filter out high-frequency noise.
Output Capacitor
The MIC23163/4 is designed for use with a 10µF or
greater ceramic output capacitor. Increasing the output
capacitance will lower output ripple and improve load
transient response but could also increase solution size
or cost. A lo w equiv alent se ries r esistanc e (ESR) cera m ic
output capacitor such as the Murata
GRM188R60J106ME84D, size 0603, 10µF ceramic
capacitor is r ecom m ended based up on perfor m ance, size
and cost. Both the X7R or X5R temperature rating
capacitors are recommended. The Y5V and Z5U
temperature rating capacitors are not recommended due
to their wide variation in capacitance over temperature
and increased resistance at high frequencies.
Inductor Selection
W hen selecting an ind uctor , it is im portant to c onsider the
following factors (not necessarily in the order of
importance):
• Rated current value
• Size requirements
• DC resistance (DCR)
The MIC23163/4 is designed for use with a 0.47µH
inductor. This allows for rapid output voltage recovery
during line and load transients.
Maximum current ratings of the inductor are generally
given in two methods; permissible DC current and
saturation current. Permissible DC current can be rated
either for a 40°C temperature rise or a 10% to 20% loss
in inductance. Ensure the inductor selected can handle
the maximum operating current. When saturation current
is specified, make sure that there is enough margin so
that the peak current does not cause the inductor to
saturate. Peak current can be calculated as illustrated in
Equation 2:
×
×
−
+
=L
f2 /VV1
V
II INOUT
OUTOUT
PEAK
Eq. 2
As shown by Equation 2, the peak inductor current is
inversely proportional to the switching frequency and the
inductance; the lower the switching frequency or the
inductance the higher the peak current. As input voltage
increases, the peak current also increases.
The size of the inductor depends on the requirements of
the application. Refer to the “Typical Application Circuit”
and “Bill of Materials” sections for details.
DC resistance (DCR) is also important. While DCR is
inversely proportional to size, DCR can represent a
significant efficiency loss. Refer to the “Efficiency
Considerations” section for more details.
The trans ition between high loa ds (CCM) to HLL m ode is
determined by the inductor ripple current and the load
current.
Figure 2. Signals for High-Side Switch Drive (HSD) for TON
Control, Inductor Current, and Low-Side Switch Drive (LSD)
for TOFF Control
Micrel, Inc.
MIC23163/4
Jul y 2
9, 2013 14 Revision 2.0
In HLL mode, the inductor is charged with a fixed Ton
pulse on the high-side switch (HSD). After this, the LSD
is switched on and current falls at a rate VOUT/L. The
controller remains in HLL mode while the inductor falling
current is detected to cross approximately −50m A. W hen
the LSD (or TOFF) time reaches its minimum and the
inductor falling current is no longer able to reach this
−50mA thr eshold, the p art is in CC M m ode and switc hing
at a virtually constant frequency.
Once in CCM mode, the TOFF time will not vary.
Compensation
The MIC23163/4 is designed to be stable with a 0.47µH
inductor with a 10µF ceramic (X5R) output capacitor. A
feed-forward capacitor in the range of 15pF to 68pF is
essential across the top feedback resistor.
Du ty C yc le
The maximum duty cycle of the MIC23163/4 is 100%,
allowing operation in dropout to extend battery life.
Efficiency Consideratio n s
Efficiency is defined as the amount of useful output
power, divided by the amount of power supplied, as
shown in Equati on 3:
100
IV IV
%
Efficiency ININ
OUT
OUT ×
×
×
=
Eq. 3
Maintaining high efficiency serves two purposes. It
reduces power dissipation in the power supply, reducing
the need for heat sinks and thermal design
considerations and it reduces consumption of current for
battery-powered applicat ions . Reduce d curr ent dra w from
a battery increases the device’s operating time and is
critic a l in handheld de vices.
There ar e t wo t ypes of losses in sw itchi ng c on vert er s; D C
losses and switching losses. DC losses are simply the
power dissipation of I2R. Power is dissipated in the high
side switch dur i ng the o n cyc le. P o wer loss is equa l to the
high sid e MOSFET RDSON multiplied by the s witch current
squared. During the off cycle, the low side N-channel
MOSFET conducts, also dissipating power. Device
operating current also reduces efficiency. The product of
the quiescent (operating) current and the supply voltage
represents another DC loss. The current required driving
the gates on and off at a constant 4MHz frequency and
the switching transitions make up the switching losses.
Figure 3. Efficiency under Load
Figure 3 shows an efficiency curve. From no load to
100mA, efficiency losses are dominated by quiescent
current losses, gate drive and transition losses. By using
the HLL mode, the MIC23163/4 is able to maintain high
efficiency at low output currents.
Over 100mA, efficiency loss is dominated by MOSFET
RDSON and inductor losses. Higher input supply voltages
will increase the gate-to-source threshold on the internal
MOSFETs, thereby reducing the internal RDSON. This
improves efficiency by reducing DC losses in the device.
All but the inductor losses are inherent to the device. In
which case, inductor selection becomes increasingly
critical in efficiency calculations. As the inductors are
reduced in size, the DC resistance (DCR) can become
quite sign ificant. The DCR loss es can be calculate d as in
Equation 4:
DCRIP
2
OUTDCR
×=
Eq. 4
From that, the loss in ef f iciency due to ind uc tor r es istan c e
can be calculated as in Equation 5:
100
PIV IV
1Loss Efficiency
DCROUTOUT
OUTOUT
×
+×
×
−=
Eq. 5
Efficiency loss due to DCR is minimal at light loads and
gains significance as the load is increased. Inductor
selection becomes a trade-off between efficiency and
size in this case.
50
55
60
65
70
75
80
85
90
95
110 100 1000 10000
EFFICIENCY (%)
OUTPUT CURRENT (mA)
Efficie nc y vs. Output Cur rent
V
OUT
= 1.8V @ 25°C
VIN = 3V
VIN = 3.6V VIN = 5V
Micrel, Inc.
MIC23163/4
Jul y 2
9, 2013 15 Revision 2.0
HyperLight Load Mode
MIC23163/4 uses a minimum on and off time proprietary
control loop (PCL) patented by Micrel called HyperLight
Load (HLL). 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 t hreshold. 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 MIC23163/4 works in pulse
frequency modulation (PFM) to regulate the output. As
the output curren t increases, the off -time decreas es, thus
provides more energy to the output. This switching
scheme improves the efficiency of MIC23163/4 during
light load cur rent s b y only s witc hing when it is needed . As
the load current increases, the MIC23163/4 goes into
continuous conduction mode (CCM) and switches at a
frequency centered at 4MHz. The equation to calculate
the load when the MIC23163/4 goes into continuous
conduction mode may be approximated by Equation 6:
()
×
×
−
>fL2 D
V
V
IOUTIN
LOAD
Eq. 6
As shown in Equation 6, the load at which the
MIC2316 3/4 tr ansitio ns f rom HLL m ode to PW M m ode is
a functio n of th e inp ut vo lta ge ( VIN), o utpu t vo ltag e ( VOUT),
duty cycle (D), inductance (L) and frequency (f). As
shown in Figure 4, as the output current increases, the
switching frequency also increases until the MIC23163/4
goes from HLL mode to PWM mode at approximately
120mA. The MIC23163/4 will switch at a relatively
constant f requenc y around 4MHz onc e the outp ut curr ent
is over 120mA.
Figure 4. SW Frequency vs. Output Current
1
10
100
1000
10000
110 100 1000 10000
SW FREQUENCY (kHz)
OUPUT CURRENT (mA)
Switching Frequency vs.
Output Curre nt
VIN = 5V
VIN = 3.6V
Micrel, Inc.
MIC23163/4
Jul y 2
9, 2013 16 Revision 2.0
Typical Applic ation Circuit
Bill of Materials
Item Part Number Manufacturer Description Qty.
C1 C1608X5R0J475K TDK
(7)
4.7µF, 6.3V, X5R, Size 0603 1
GRM188R60J475KE19D Murata
(8)
C2 C1608X5R0J106K080AB TDK 10µF, 6.3V, X5R, Size 0603 1
GRM188R60J106ME84D Murata
C3 GRM188R71H102MA01D Murata 1nF/50V, X7R, 0603 1
06035C102KAT2A AVX(9)
C4 06035A150KAT2A AVX 15pF, 50V, 0603 1
GRM1885C1H150JA01D Murata
L1 FLF3215T-R47N TDK 0.47µH, 2.8A, 21mΩ, L3.2mm × W2.5mm × H1.55mm 1
LQH32PNR47NNC Murata 0.47µH, 2.9A, 24mΩ, L3.2mm × W2.5mm × H1.55mm
R1 CRCW0603301KFKEA Vishay(
10
) 301kΩ, 1%, 1/10W, Size 0603 1
R2 CRCW0603158KFKEA Vishay 158kΩ, 1%, 1/10W, Size 0603 1
R3, R4 CRCW0603100KFKEA Vishay 100kΩ, 1%, 1/10W, Size 0603 1
R5 CRCW060310R0FKEA Vishay 10Ω, 1%, 1/10W, Size 0603 1
U1
MIC23163YMT
Micrel, Inc.(11) 4MHz, 2A, 100% Dut y Cycle Buck Regulator with
HyperLight Load® and Power Good 1
MIC23164YMT
Notes:
7. TDK: www.tdk.com.
8. Murata: www.murata.com.
9. AVX: www.avx.com.
10. Vishay: www.vishay.com.
11. Micrel, Inc.: www.micrel.com.
Micrel, Inc.
MIC23163/4
Jul y 2
9, 2013 17 Revision 2.0
PCB Layout Recommendations
Top Layer
Bottom Layer
Micrel, Inc.
MIC23163/4
Jul y 2
9, 2013 19 Revision 2.0
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nd Purchaser agrees to fully
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