MIC23158 DATA SHEET (11/05/2015) DOWNLOAD

MIC23158/9
3MHz PWM Dual 2A Buck Regulator with
HyperLight Load and Power Good
General Description
Features
The MIC23158/9 is a high-efficiency, 3MHz, dual, 2A
synchronous buck regulator with HyperLight Load mode,
power good output indicator, and programmable soft start.
The MIC23159 also provides an auto discharge feature
that switches in a 225Ω pull down circuit on its output to
discharge the output capacitor when disabled. HyperLight
Load provides very high efficiency at light loads and ultrafast transient response which makes the MIC23158/9
perfectly suited for supplying processor core voltages. An
additional benefit of this proprietary architecture is very low
output ripple voltage throughout the entire load range with
the use of small output capacitors. The 20-pin 3mm x 4mm
®
MLF package saves precious board space and requires
seven external components for each channel.
The MIC23158/9 is designed for use with a very small
inductor, down to 0.47µH, and an output capacitor as small
as 2.2µF that enables a total solution size, less than 1mm
in height.
The MIC23158/9 has a very low quiescent current of 45µA
and achieves a peak efficiency of 94% in continuous
conduction mode. In discontinuous conduction mode, the
MIC23158/9 can achieve 83% efficiency at 1mA.
The MIC23158/9 is available in a 20-pin 3mm x 4mm MLF
package with an operating junction temperature range
from –40°C to +125°C.
Datasheets and support documentation can be found on
Micrel’s web site at: www.micrel.com.
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2.7V to 5.5V input voltage
Adjustable output voltage (down to 1.0V)
2 independent 2A outputs
Up to 94% peak efficiency
83% typical efficiency at 1mA
2 independent power good indicators
Independent programmable soft start
45µA typical quiescent current
3MHz PWM operation in continuous conduction mode
Ultra-fast transient response
Fully-integrated MOSFET switches
Output pre-bias safe
0.1µA shutdown current
Thermal-shutdown and current-limit protection
20-pin 3mm x 4mm MLF package
Internal 225Ω pull-down circuit on output (MIC23159)
–40°C to +125°C junction temperature range
Applications
• Solid State Drives (SSD)
• Smart phones
• Tablet PCs
• Mobile handsets
• Portable devices (PMP, PND, UMPC, GPS)
• WiFi/WiMax/WiBro applications
_______________________________________________________________________________________________________
Typical Application
HyperLight Load is a registered trademark of Micrel, Inc.
MLF and MicroLeadFrame are registered trademarks 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
November 2012
M9999-110812-A
Micrel Inc.
MIC23158/9
Ordering Information
Nominal Output Voltage
VOUT1
VOUT2
Output
Auto
Discharge
MIC23158YML
ADJ
ADJ
NO
–40°C to +125°C
20-Pin 3mm x 4mm MLF
MIC23159YML
ADJ
ADJ
YES
–40°C to +125°C
20-Pin 3mm x 4mm MLF
Part Number
Junction Temperature Range
Package
Notes:
1.
Fixed output voltage options available. Contact Micrel Marketing for details.
2.
MLF is a GREEN RoHS-compliant package. Lead finish is NiPdAu. Mold compound is Halogen Free.
AVIN1
AGND1
EN1
SNS1
Pin Configuration
20
19
18
17
VIN1
11
16
FB1
PGND1
2
15
PG1
SW1
3
14
SS1
SW2
4
13
SS2
PGND2
5
12
PG2
VIN2
6
11
FB2
7
8
9
10
AVIN2
AGND2
EN2
SNS2
EP
3mm x 4mm MLF (ML) Adjustable Output Voltage
(Top View)
Pin Description
Pin Number
(Adjustable)
Pin Name
1
VIN1
2
PGND1
3
SW1
Switch (Output): Internal power MOSFET output switches for regulator 1.
4
SW2
Switch (Output): Internal power MOSFET output switches for regulator 2.
5
PGND2
6
VIN2
7
AVIN2
November 2012
Pin Function
Power Input Voltage for Regulator 1. Connect a capacitor to ground to decouple noise and switching
transients.
Power Ground for Regulator 1.
Power Ground for Regulator 2.
Power Input Voltage for Regulator 2. Connect a capacitor to ground to decouple noise and switching
transients.
Analog Input Voltage for Regulator 2. Tie to VIN2 and connect a capacitor to ground to decouple
noise.
2
M9999-110812-A
Micrel Inc.
MIC23158/9
Pin Description (Continued)
Pin Number
(Adjustable)
Pin Name
8
AGND2
9
EN2
10
SNS2
Sense Input for Regulator 2. Connect to the output of regulator 2 as close to the output capacitor as
possible to accurately sense the output voltage.
11
FB2
Feedback Input for Regulator 2. Connect a resistor divider from the output of regulator 2 to ground to
set the output voltage.
12
PG2
Power Good Output for Regulator 2. Open drain output for the power good indicator for output 2. Use
a pull-up resistor between this pin and VOUT2 to indicate a power good condition.
13
SS2
Soft-Start for Regulator 2. Connect a minimum of 200pF capacitor to ground to set the turn-on time of
regulator 2. Do not leave floating.
14
SS1
Soft-Start for Regulator 1. Connect a minimum of 200pF capacitor to ground to set the turn-on time of
regulator 1. Do not leave floating.
15
PG1
Power Good Output for Regulator 1. Open drain output for the power good indicator for output 1. Use
a pull-up resistor between this pin and VOUT1 to indicate a power good condition.
16
FB1
Feedback Input for Regulator 1. Connect a resistor divider from the output of regulator 1 to ground to
set the output voltage.
17
SNS1
Sense Input for Regulator 1. Connect to the output of regulator 1 as close to the output capacitor as
possible to accurately sense the output voltage.
18
EN1
19
AGND1
Analog Ground for Regulator 1. Connect to a central ground point where all high current paths meet
(CIN, COUT, PGND1) for best operation.
20
AVIN1
Analog Input Voltage for Regulator 1. Tie to VIN1 and connect a capacitor to ground to decouple
noise.
EP
ePad
Exposed Heat Sink Pad. Connect to PGND.
November 2012
Pin Function
Analog Ground for Regulator 2. Connect to a central ground point where all high current paths meet
(CIN, COUT, PGND2) for best operation.
Enable Input for Regulator 2. Logic high enables operation of regulator 2. Logic low will shut down
regulator 2. Do not leave floating.
Enable Input for Regulator 1. Logic high enables operation of regulator 1. Logic low will shut down
regulator 1. Do not leave floating.
3
M9999-110812-A
Micrel Inc.
MIC23158/9
(1)
(2)
Absolute Maximum Ratings
Operating Ratings
Supply Voltage (AVIN1, AVIN2, VIN1, VIN2).... −0.3V to 6V
Switch1 (VSW1), Sense1 (VSNS1)......................−0.3V to VIN1
Enable1 (VEN1), Power Good1 (VPG1) .............−0.3V to VIN1
Feedback1 (VFB1) ......................................... −-0.3V to VIN1
Switch2 (VSW2), Sense2 (VSNS2)...................... -0.3V to VIN2
Enable2 (VEN2), Power Good2 (VPG2) .............−0.3V to VIN2
Feedback2 (VFB2) ...........................................−0.3V to VIN2
Power Dissipation TA = 70°C .................... Internally Limited
Storage Temperature Range .................... −65°C to +150°C
Lead Temperature (soldering, 10s) ............................ 260°C
(3)
ESD Rating ..................................................ESD sensitive
Supply Voltage (AVIN1, VIN1) ..................... +2.7V to +5.5V
Supply Voltage (AVIN2, VIN2) ..................... +2.7V to +5.5V
Enable Input Voltage (VEN1, VEN2) ...................... 0V to VIN1,2
Output Voltage Range (VSNS1, VSNS2) .......... +1.0V to +3.3V
Junction Temperature Range (TJ) ...... −40°C ≤ TJ ≤ +125°C
Thermal Resistance
3mm x 4mm MLF-20 (θJA) ................................. 53°C/W
Electrical Characteristics(4)
TA = 25°C; AVIN1,2 = VIN1,2 = VEN1,2 = 3.6V; L1,2 = 1.0µH; COUT1,2 = 4.7µF unless otherwise specified.
Bold values indicate –40°C ≤ TJ ≤ +125°C, unless noted.
Parameter
Condition
Min.
Undervoltage Lockout Threshold
Typ.
2.7
Supply Voltage Range
2.45
Rising
Undervoltage Lockout Hysteresis
2.55
Max.
Units
5.5
V
2.65
V
75
mV
Quiescent Current
IOUT = 0mA , SNS > 1.2 * VOUTNOM (both outputs)
45
90
µA
Shutdown Current
VEN = 0V; VIN = 5.5V (per output)
0.1
5
µA
Feedback Regulation Voltage
IOUT = 20mA
0.62
0.6355
V
Feedback Bias Current
(per output)
Current Limit
SNS = 0.9*VOUTNOM
Output Voltage Line Regulation
Output Voltage Load Regulation
PWM Switch RDSON
0.6045
0.01
µA
4.3
A
VIN = 3.6V to 5.5V if VOUTNOM < 2.5V, IOUT = 20mA
VIN = 4.5V to 5.5V if VOUTNOM ≥ 2.5V, IOUT = 20mA
0.45
%/V
DCM, VIN = 3.6V if VOUTNOM < 2.5V
0.55
DCM, VIN = 5.0V if VOUTNOM ≥ 2.5V
1.0
2.2
CCM, VIN = 3.6V if VOUTNOM < 2.5V
CCM, VIN = 5.0V if VOUTNOM ≥ 2.5V
ISW1,2 = 100mA PMOS
0.20
ISW1,2 = -100mA NMOS
0.19
Switching Frequency
IOUT = 180mA
Soft-Start Time
VOUT = 90%, CSS = 470pF
Soft-Start Current
VSS = 0V
0.8
Ω
3
MHz
300
µs
2.7
Power Good Threshold (Rising)
86
Power Good Threshold Hysteresis
Power Good Delay Time
%
Rising
Power Good Pull-Down Resistance
92
µA
96
%
7
%
68
µs
95
Ω
Notes:
1.
Exceeding the absolute maximum rating may damage the device.
2.
The device is not guaranteed to function outside its operating rating.
3.
Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5kΩ in series with 100pF.
4.
Specification for packaged product only.
November 2012
4
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Micrel Inc.
MIC23158/9
Electrical Characteristics(4) (Continued)
TA = 25°C; AVIN1,2 = VIN1,2 = VEN1,2 = 3.6V; L1,2 = 1.0µH; COUT1,2 = 4.7µF unless otherwise specified.
Bold values indicate –40°C ≤ TJ ≤ +125°C, unless noted.
Parameter
Condition
Min.
Enable Input Voltage
Typ.
Max.
0.4
Logic Low
1.2
Logic High
Enable Input Current
0.1
2
Units
V
µA
225
Ω
Overtemperature Shutdown
160
°C
Shutdown Hysteresis
20
°C
Output Discharge Resistance
November 2012
MIC23159 Only; EN = 0V, IOUT = 250µA
5
M9999-110812-A
Micrel Inc.
MIC23158/9
Typical Characteristics
100
90
90
80
80
VIN = 4.2V
70
VIN = 5V
EFFICIENCY (%)
EFFICIENCY (%)
100
Efficiency (VOUT = 2.5V) vs.
Output Current
60
50
40
30
20
90
80
70
VIN = 4.2V
VIN = 3.6V
VIN = 5V
60
50
40
30
20
COUT=4.7µF
L=1µH
10
10
100
1000
100
VIN = 5V
VIN = 4.2V
50
40
30
COUT=4.7µF
L=1µH
10
100
1000
1
10000
10
100
1000
10000
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
Current Limit
vs. Input Voltage
VOUT Rise Time
vs. CSS
Efficiency (VOUT = 1.5V) vs.
Output Current
VIN = 3.6V
0
1
10000
VIN = 2.7V
60
10
0
1
70
20
COUT=4.7µF
L=1µH
10
0
Efficiency (VOUT = 1.8V) vs.
Output Current
100
EFFICIENCY (%)
Efficiency (VOUT = 3.3V) vs.
Output Current
6.0
1000000
100000
70
RISE TIME (µs)
EFFICIENCY (%)
80
CURRENT LIMIIT (A)
90
VIN = 3.6V
60
VIN = 5V
VIN = 2.7V
VIN = 4.2V
50
40
10000
1000
30
20
100
COUT=4.7µF
L=1µH
10
0
1
100
10
1000
VOUT = 1.8V
COUT = 4.7µF
10
100
10000
VOUT = 1.8V
COUT = 4.7µF
1.0
10000
100000
1000000
2.5
3.0
50
T = 25°C
45
40
T = -40°C
No Switching
SNS > VOUTNOM * 1.2
COUT = 4.7µF
4.0
3.0
3.5
4.0
4.5
5.0
5.5
November 2012
5.5
1.95
100
10
1.90
IOUT = 300mA
IOUT = 1A
1.85
1.80
1.75
1.70
VOUTNOM = 1.8V
1.65
1
COUT = 4.7µF
1.60
2.5
INPUT VOLTAGE (V)
5.0
2.00
20
2.5
4.5
Line Regulation
(CCM)
OUTPUT VOLTAGE (V)
55
3.5
INPUT VOLTAGE (V)
1000
T = 125°C
SHUTDOWN CURRENT (nA)
QUIESCENT CURRENT (µA)
2.0
Shutdown Current
vs. Input Voltage
60
25
3.0
CSS (pF)
Quiescent Current
vs. Input Voltage
30
4.0
0.0
1000
OUTPUT CURRENT (mA)
35
5.0
3.0
3.5
4.0
4.5
INPUT VOLTAGE (V)
6
5.0
5.5
2.5
3.0
3.5
4.0
4.5
5.0
5.5
INPUT VOLTAGE (V)
M9999-110812-A
Micrel Inc.
MIC23158/9
Typical Characteristics (Continued)
Load Regulation
(CCM)
2.00
1.95
1.95
1.95
1.90
IOUT = 80mA
IOUT = 20mA
1.85
1.80
1.75
IOUT = 1mA
1.70
VOUTNOM = 1.8V
3.0
3.5
4.0
4.5
5.0
1.85
1.80
1.75
VIN = 3.6V
1.70
5.5
1.90
1.85
1.80
1.75
COUT = 4.7µF
VOUTNOM =1.8V
1000
1400
60
80
100
120
Switching Frequency
vs. Temperature
5
FEEDBACK VOLTAGE (V)
IOUT = 400mA
3.5
IOUT = 1.2A
2.5
2.0
TA = 25°C
SWITCHING FREQUENCY (MHz)
0.65
IOUT = 100mA
1.5
40
OUTPUT CURRENT (mA)
Feedback Voltage
vs. Temperature
5.0
3.0
20
1800
OUTPUT CURRENT (mA)
VOUTMAX vs. VIN
4.0
COUT = 4.7µF
1.60
0
600
INPUT VOLTAGE (V)
4.5
VIN = 3.6V
1.70
1.65
VOUTNOM = 1.8V
1.60
200
1.60
2.5
1.90
1.65
COUT = 4.7µF
OUTPUT VOLTAGE (V)
2.00
1.65
OUTPUT VOLTAGE (V)
Load Regulation
(HLL)
2.00
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
Line Regulation
(HLL)
0.64
0.63
0.62
0.61
VIN = 3.6V
0.60
VOUT = 1.8V
4
3
2
VIN = 3.6V
1
VOUTNOM = 1.8V
COUT = 4.7µF
0
1.0
0.59
2.5
3.0
3.5
4.0
4.5
INPUT VOLTAGE (V)
November 2012
5.0
5.5
-40
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
7
100
-20
0
20
40
60
80
100
120
120
TEMPERATURE (°C)
M9999-110812-A
Micrel Inc.
MIC23158/9
Functional Characteristics
November 2012
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Micrel Inc.
MIC23158/9
Functional Characteristics (Continued)
November 2012
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Micrel Inc.
MIC23158/9
Functional Characteristics (Continued)
November 2012
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Micrel Inc.
MIC23158/9
Functional Diagram
Figure 1. Simplified MIC23158 Functional Block Diagram – Adjustable Output Voltage
November 2012
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Micrel Inc.
MIC23158/9
Functional Diagrams (Continued)
Figure 2. Simplified MIC23159 Functional Block Diagram – Adjustable Output Voltage
November 2012
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M9999-110812-A
Micrel Inc.
MIC23158/9
PGND
The power ground pin is the ground path for the high
current in PWM mode. The current loop for the power
ground should be as small as possible and separate
from the analog ground (AGND) loop as applicable.
Refer to the layout recommendations for more details.
Functional Description
VIN
The input supply (VIN) provides power to the internal
MOSFETs for the switch mode regulator section. The
VIN operating range is 2.7V to 5.5V. 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 close to VIN and the power
ground (PGND) pin is required. Refer to the PCB Layout
Recommendations for details.
PG
The power good (PG) pin is an open drain output which
indicates when the output voltage is within regulation.
This is indicated by a logic high signal when the output
voltage is above the PG threshold. Connect a pull up
resistor greater than 5kΩ from PG to VOUT.
AVIN
Analog VIN (AVIN) provides power to the internal control
and analog supply circuitry. AVIN and VIN must be tied
together. Careful layout should be considered to ensure
high frequency switching noise caused by VIN is
reduced before reaching AVIN. A 1µF capacitor as close
to AVIN as possible is recommended. Refer to the PCB
Layout Recommendations for details.
SS
An external soft start circuitry set by a capacitor on the
SS pin reduces inrush current and prevents the output
voltage from overshooting at start up. The SS pin is used
to control the output voltage ramp up time and the
approximate equation for the ramp time in milliseconds
3
is 296 x 10 x ln(10) x CSS. For example, for a CSS =
470pF, TRISE ≈ 300µs. Refer to the “VOUT Rise Time vs.
CSS” graph in the Typical Characteristics section. The
minimum recommended value for CSS is 200pF.
EN
A logic high signal on the enable pin activates the output
voltage of the device. A logic low signal on the enable
pin deactivates the output and reduces supply current to
0.1µA. Do not leave the EN pin floating. When disabled,
the MIC23159 switches in a 225Ω load from the SNS pin
to AGND, to discharge the output capacitor.
FB
The feedback (FB) pin is provided for the adjustable
voltage option. This is the control input for setting the
output voltage. A resistor divider network is connected to
this pin from the output and is compared to the internal
0.62V reference within the regulation loop.
The output voltage can be calculated using Equation 1:
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.
R1 

VOUT = VREF ⋅ 1 +

R2 

SNS
The sense (SNS) pin is connected to the output of the
device to provide feedback to the control circuitry. The
SNS connection should be placed close to the output
capacitor. Refer to the layout recommendations for more
details. The SNS pin also provides the output active
discharge circuit path to pull down the output voltage
when the device is disabled.
Recommended feedback resistor values:
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 for details.
November 2012
Eq. 1
13
VOUT
R1
R2
1.2V
274k
294k
1.5V
316k
221k
1.8V
301k
158k
2.5V
324k
107k
3.3V
309k
71.5k
M9999-110812-A
Micrel Inc.
MIC23158/9
Peak current can be calculated in Equation 2:
Application Information
The MIC23158/9 is a high-performance DC/DC step
down regulator offering a small solution size. Supporting
two outputs of up to 2A each in a 3mm x 4mm MLF
package. Using the HyperLight Load switching scheme,
the MIC23158/9 is able to maintain high efficiency
throughout the entire load range while providing ultra
fast load transient response. The following sections
provide additional device application information.

 1 − VOUT /VIN
IPEAK = IOUT + VOUT 
 2× f ×L




Eq. 2
As shown by the calculation above, the peak inductor
current is inversely proportional to the switching
frequency and the inductance. The lower the switching
frequency or 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 for details.
Input Capacitor
A 2.2µF ceramic capacitor or greater should be placed
close to the VIN pin and PGND pin for bypassing. A
Murata GRM188R60J475KE19D, size 0603, 4.7µF
ceramic capacitor is recommended based upon
performance, size and cost. A X5R or X7R temperature
rating is recommended for the input capacitor.
Output Capacitor
The MIC23158/9 is designed for use with a 2.2µF 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 low equivalent series resistance (ESR)
ceramic output capacitor such as the Murata
GRM188R60J475KE19D, size 0603, 4.7µF ceramic
capacitor is recommended based upon performance,
size and cost. Both the X7R or X5R temperature rating
capacitors are recommended.
Inductor Selection
When selecting an inductor, it is important to consider
the following factors:
•
Inductance
•
Rated current value
•
Size requirements
•
DC resistance (DCR)
Figure 3. Transition between CCM Mode to HLL Mode
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” subsection.
The transition between continuous conduction mode
(CCM) to HyperLight Load mode is determined by the
inductor ripple current and the load current.
The diagram shows the signals for high-side switch drive
(HSD) for TON control, the Inductor current, and the lowside switch drive (LSD) for TOFF control.
In HLL mode, the inductor is charged with a fixed TON
pulse on the high side switch. After this, the low side
switch is turned 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 -50mA. When
the LSD (or TOFF) time reaches its minimum and the
inductor falling current is no longer able to reach the
threshold, the part is in CCM mode.
The MIC23158/9 is designed for use with a 0.47µH to
2.2µH inductor. For faster transient response, a 0.47µH
inductor will yield the best result. For lower output ripple,
a 2.2µH inductor is recommended.
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.
November 2012
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Micrel Inc.
MIC23158/9
Figure 4 shows an efficiency curve. From 1mA load to
2A, efficiency losses are dominated by quiescent current
losses, gate drive and transition losses. By using the
HyperLight Load mode, the MIC23158/9 is able to
maintain high efficiency at low output currents.
Over 180mA, 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 significant. The DCR losses can be calculated as in
Equation 5:
Once in CCM mode, the TOFF time will not vary.
Therefore, it is important to note that if L is large enough,
the HLL transition level will not be triggered.
That inductor is illustrated in Figure 3:
L MAX =
VOUT − 135ns
Eq. 3
2 − 50mA
Duty Cycle
The typical maximum duty cycle of the MIC23158/9 is
80%.
Efficiency Considerations
Efficiency is defined as the amount of useful output
power, divided by the amount of power supplied.
2
PDCR = IOUT x DCR
V
×I
Efficiency % =  OUT OUT
×
V
IN IIN


 × 100

Eq. 4
From that, the loss in efficiency due to inductor
resistance can be calculated as in Equation 6:
There are two types of losses in switching converters;
DC losses and switching losses. DC losses are simply
2
the power dissipation of I R. Power is dissipated in the
high side switch during the on cycle. Power loss is equal
to the high side MOSFET RDSON multiplied by the switch
current squared. During the off cycle, the low side Nchannel 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 3MHz
frequency and the switching transitions make up the
switching losses.
 
VOUT × IOUT
Efficiency Loss = 1 − 
V
  OUT × IOUT + PDCR
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.
HyperLight Load Mode
The MIC23158/9 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 an 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 MIC23158/9
works in HyperLight Load 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 MIC23158/9 during
light load currents by only switching when it is needed.
90
EFFICIENCY (%)
80
70
VIN = 2.7V
60
VIN = 3.6V
VIN = 5V
VIN = 4.2V
50
40
30
20
COUT=4.7µF
L=1µH
10
0
1
10
100
1000
10000
OUTPUT CURRENT (mA)
Figure 4. Efficiency under Load
November 2012

 × 100


Eq. 6
Efficiency (VOUT = 1.8V) vs.
Output Current
100
Eq. 5
15
M9999-110812-A
Micrel Inc.
MIC23158/9
As the load current increases, the MIC23158/9 goes into
continuous conduction mode (CCM) and switches at a
frequency centered at 3MHz. The equation to calculate
the load when the MIC23158/9 goes into continuous
conduction mode may be approximated by the following
formula:
 (V − VOUT ) × D 
ILOAD >  IN

2L × f


Eq. 7
As shown in Equation 7, the load at which the
MIC23158/9 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 Figure 5, as the output
current increases, the switching frequency also
increases until the MIC23158/9 goes from HyperLight
Load mode to PWM mode at approximately 180mA. The
MIC23158/9 will switch at a relatively constant frequency
around 3MHz once the output current is over 180mA.
Switching Frequency
vs. Output Current
SWITCHING FREQUENCY (MHz)
5.0
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
0.1
1
10
100
1000
10000
OUTPUT CURRENT (mA)
Figure 5. SW Frequency vs. Output Current
November 2012
16
M9999-110812-A
Micrel Inc.
MIC23158/9
Typical Application Circuit (Adjustable Output)
Bill of Materials
Item
C1, C2
C3, C4, C5, C6
C7, C8
L1, L2
R1
R2
R3
R4
R5, R6
R7, R8
Part Name
06036D105KAT2A
GRM188R60J105KA01D
C1608X5R0J105K
06036D475KAT2A
GRM188R60J475KE19D
C1608X5R0J475K
06035A471JAT2A
GRM1885C1H471JA01D
C1608C0G1H471J
CDRH4D28CLDNP-1R0P
LQH44PN1R0NJ0
CRCW06033013FKEA
CRCW06031583FKEA
CRCW06033163FKEA
CRCW06032213FKEA
CRCW06031003FKEA
CRCW06031002FKEA
U1
MIC23158/9YML
Manufacturer
(1)
AVX
(2)
Murata
(3)
TDK
AVX
Murata
TDK
AVX
Murata
TDK
(4)
SUMIDA
MURATA
(5)
Vishay/Dale
Vishay/Dale
Vishay/Dale
Vishay/Dale
Vishay/Dale
Vishay/Dale
Micrel, Inc
(6)
Description
Qty.
1µF, 0603, 6.3V
2
4.7µF, 6.3V, X5R, 0603
4
470pF, 50V, 0603
2
1µH, 3.0A, 14mΩ, L5.1mm x W5.1mm x H3.0mm
1µH, 2.8A, 14mΩ, L5.1mm x W5.1mm x H3.0mm
301KΩ, 1%, 1/10W, 0603
158KΩ, 1%, 1/10W, 0603
316KΩ, 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
2
1
1
1
1
2
2
1
Notes:
1.
AVX: www.avx.com.
2.
Murata: www.murata.com.
3.
TDK: www.tdk.com.
4.
Sumida: www.sumida.com.
5.
Vishay/Dale: www.vishay.com.
6.
Micrel, Inc.: www.micrel.com.
November 2012
17
M9999-110812-A
Micrel Inc.
MIC23158/9
PCB Layout Recommendations
Top Layer
Bottom Layer
November 2012
18
M9999-110812-A
Micrel Inc.
MIC23158/9
Package Information(1)
20-Pin 3mm x 4mm MLF
Note:
1.
Package information is correct as of the publication date. For updates and most current information, go to www.micrel.com.
November 2012
19
M9999-110812-A
Micrel Inc.
MIC23158/9
Recommended Land Pattern
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.
© 2012 Micrel, Incorporated.
November 2012
20
M9999-110812-A