Micrel MIC2811 Digital power management ic 2mhz, 600ma dc/dc with triple 300ma ldo Datasheet

MIC2811/2821
Digital Power Management IC
2MHz, 600mA DC/DC with
Triple 300mA LDOs
General Description
The MIC2811/21 are high performance power
management ICs, supporting four output voltage rails with
maximum efficiency. The four rails are generated by a
single 600mA DC/DC converter and three 300mA LDOs.
LDO1 and LDO2 are capable of operating at a low input
voltage down to 1.65V useful for post regulating the output
voltage of the DC-DC converter. The MIC2811 supports
the use of a bypass cap for improved noise performance
on LDO1 & LDO2 while the MIC2821 offers a separate
enable pin for LDO3.
Featuring an operating frequency of 2MHz, the DC to DC
converter uses small values of L and C to reduce board
space but still retains operating efficiencies up to 86% at
load currents up to 600mA.
The MIC2811/21 feature a µCap design, operating with
very small ceramic output capacitors and inductors for
stability, reducing required board space and component
cost and it is available in fixed output voltages in the 16pin 3mm × 3mm MLF® leadless package.
Data sheets and support documentation can be found on
Micrel’s web site at: www.micrel.com.
Applications
Features
•
•
•
•
•
2MHz DC/DC converter and 3 LDOs
Tiny 16-pin 3mm x 3mm MLF® package
Thermal Shutdown Protection
±2% Output Voltage Accuracy on all outputs
Current Limit Protection
DC/DC Converter
•
•
•
•
2.7V to 5.5V input voltage range
Output current to 600mA
2MHz PWM operation
Up to 86% efficiency (1.2V output)
LDO 1 & 2
•
•
•
•
•
1.65V to 5.5V input voltage range
300mA output current
Fixed Output voltage as low as 0.8V
Low 142mV dropout
70dB PSRR at 1kHz
LDO 3
•
•
•
2.7V to 5.5V input voltage range
300mA output current
Fixed Output voltage as low as 1.0V
• Mobile phones / PDAs
• Portable media players
• Mobile Television Receivers
____________________________________________________________________________________________________________
Typical Application
1.2VOUT Efficiency
100
90
EFFICIENCY (%)
80
70
60
3V
3.6V
4.2V
50
40
30
20
10
0
0
L = 2.2µH
C = 2.2µF
100 200 300 400 500 600
OUTPUT CURRENT (mA)
MicroLeadFrame and MLF are registered 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
April 2008
M9999-042208-A
Micrel, Inc.
MIC2811/2821
Ordering Information
(1)
Junction
Temperature
Range
Package(2)
Part Number
Marking Code
MIC2811-4GJLYML
YHA4
1.2V/1.8V/2.5V/2.7V
–40°C to +125°C
16-Pin 3x3 MLF®
MIC2811-4GMSYML
YHA3
1.2V/1.8V/2.8V/3.3V
–40°C to +125°C
16-Pin 3x3 MLF®
MIC2821-4GJLYML
YJA2
1.2V/1.8V/2.5V/2.7V
–40°C to +125°C
16-Pin 3x3 MLF®
MIC2821-4GMSYML
YJA3
1.2V/1.8V/2.8V/3.3V
–40°C to +125°C
16-Pin 3x3 MLF®
Voltage
Note:
1. Output Voltage of DC/DC, LDO1, LDO2, LDO3 respectively
For additional voltage options, contact Micrel Marketing. Available fixed output voltage range for each output is as follows:
DC/DC
LDO1
LDO2
LDO3
min
1.0
0.8
0.8
1.0
max
2.0 (Adjustable output also available)
3.6
3.6
3.9
2. MLF is a GREEN RoHS compliant package. Lead finish is NiPdAu. Mold compound is Halogen Free.
April 2008
2
M9999-042208-A
Micrel, Inc.
MIC2811/2821
FB
EN3
EN
EN2
FB
BYP
EN
EN2
Pin Configuration
EN1
VIN1
EN1
VIN1
BIAS
LDO1
BIAS
LDO1
LDO3
LDO2
MIC2811
®
16-Pin 3mm x 3mm MLF (ML)
(Top View)
LDO2
PGND
VIN2
LDO3
DVIN
PGND
SW
VIN
VIN2
SGND
DVIN
VIN
SW
SGND
MIC2821
®
16-Pin 3mm x 3mm MLF (ML)
(Top View)
Pin Description
Pin Number
MIC2811
Pin Number
MIC2821
Pin Name
1
1
EN1
Enable Input (LDO 1). Active High Input. Logic High = On; Logic Low = Off;
Do not leave floating.
2
2
BIAS
Internal circuit bias supply. It must be de-coupled to signal ground with a
0.1µF capacitor and should not be loaded.
3
3
SGND
Signal ground.
4
4
PGND
Power ground.
5
5
SW
Switch (Output): Internal power MOSFET output switches.
6
6
DVIN
Power Supply for DC/DC converter. Must be tied to VIN.
7
7
VIN2
Power Supply to LDO2.
8
8
LDO2
Output of LDO2.
9
9
LDO3
Output of LDO3.
10
10
VIN
11
11
LDO1
12
12
VIN1
13
13
FB
14
N/A
BYP
Reference Bypass. Connect external 0.1µF to GND to reduce output noise.
May be left open. Do not connect directly to GND.
N/A
14
EN3
Enable Input (LDO3). Active High Input. Logic High = On; Logic Low = Off;
Do not leave floating.
15
N/A
EN
Enable Input (DC/DC and LDO3). Active High Input. Logic High = On; Logic
Low = Off; Do not leave floating.
N/A
15
EN
Enable Input (DC/DC). Active High Input. Logic High = On; Logic Low = Off;
Do not leave floating.
16
16
EN2
Enable Input (LDO2). Active High Input. Logic High = On; Logic Low = Off;
Do not leave floating.
April 2008
Pin Name
Supply to bias circuitry and power to LDO3, must be tied to DVIN.
Output of LDO1.
Power Supply to LDO1.
Feedback input to the error amplifier of the DC/DC converter.
Adjust version: Use external resistor divider from DC/DC output to set VOUT.
Fixed voltage version: Connect directly to VOUT of the DC/DC converter.
3
M9999-042208-A
Micrel, Inc.
MIC2811/2821
Absolute Maximum Ratings(1)
Operating Ratings(2)
Supply Voltage (DVIN, VIN, VIN1, VIN2) ................... 0V to +6V
Enable Voltage (VEN, VEN1, VEN2, VEN3) ................ 0V to +6V
Power Dissipation ................................. Internally Limited(3)
Lead Temperature (Soldering, 10 sec.) ..................... 260°C
Storage Temperature (TS)...................–65°C ≤ TJ ≤ +150°C
ESD Rating(4) ................................................................. 2kV
Supply voltage (DVIN, VIN) ......................... +2.7V to +5.5V
Supply voltage (VIN1, VIN2) ............................+1.65V to VIN
Enable Input Voltage (VEN, VEN1, VEN2, VEN3) ...... 0V to VIN
Junction Temperature Range (TJ) .........–40°C to +125°C
Package Thermal Resistance
3mm x 3mm MLF-16 (θJA) .............................56°C/W
Electrical Characteristics(5)
DVIN = VIN = VIN1 = VIN2 = VOUTMAX + 1V, L = 2.2µH; COUTDC/DC = 2.2µF, COUT1 = COUT2 = COUT3 = 2.2µF; IOUTDC/DC = 20mA;
IOUTLDO1 = IOUTLDO2 = IOUTLDO2 = 100µA; TJ = 25°C, bold values indicate –40°C < TJ < +125°C; unless noted.
Parameter
Conditions
Min
Typ
Max
Units
UVLO Threshold
Rising input voltage during turn-on (DVIN & VIN Only)
2.45
2.55
2.65
V
UVLO Hysteresis
Ground Pin Current
Ground Pin Current in
Shutdown
100
mV
VFB = 1.1*VFBNOM (not switching);
800
1100
µA
LDO2 or LDO1 Only (VEN = VEN3 = GND)
55
85
95
LDO3 only (VEN = VEN1 = VEN2 = GND / MIC2821 only)
All 3 LDOs
40
120
µA
µA
µA
µA
All EN = 0V
0.2
5
µA
Over-temperature Shutdown
160
°C
Over-temperature Shutdown
Hysteresis
23
°C
Enable Input Voltage
Logic Low
Logic High
0.2
V
1
µA
V
1.1
Enable Input Current
0.1
Electrical Characteristics - DC/DC Converter
DVIN = VIN = VEN = VOUTDC/DC + 1V, L = 2.2µH; COUTDC/DC = 2.2µF, COUT1 = COUT2 = COUT3 = 2.2µF; IOUTDC/DC = 20mA; TJ = 25°C, bold
values indicate –40°C to + 125°C; unless noted.
Parameter
Output Voltage Accuracy
Current Limit in PWM Mode
Conditions
Min
Fixed Output Voltages
Typ
-2
-3
VFB = 0.9*VFBNOM
0.75
FB pin input current (ADJ only)
1.2
Max
Units
+2
+3
%
%
1.8
A
1
nA
Output Voltage Line Regulation
VOUT > 2.4V; VIN = VOUT + 300mV to 5.5V, ILOAD= 20mA
VOUT < 2.4V; VIN = 2.7V to 5.5V, ILOAD= 20mA
0.2
%/V
%/V
Output Voltage Load Regulation
20mA < ILOAD < 300mA
0.2
Maximum Duty Cycle
VFB ≤ 0.4V
Switch ON-Resistance
PMOS (0.7*VFBNOM)
NMOS (1.1*VFBNOM)
1.5
100
%
Ω
Ω
0.5
0.55
Oscillator Frequency
1.8
%
2
2.2
MHz
83
350
µs
Turn-on Time
Turn-on Time (DC/DC)
April 2008
ILOAD = 300mA; CBYP = 0.1µF
4
M9999-042208-A
Micrel, Inc.
MIC2811/2821
Electrical Characteristics - LDO1 and LDO2
VIN = DVIN = VOUTMAX + 1V, VIN1 = VEN1 = VLDO1 + 1V; VIN2 = VEN2 = VLDO2 + 1V ; COUTLDO1 = COUTLDO2 = 2.2µF, ILDO1 = ILDO2 = 100µA; TJ =
25°C, VEN = VEN3 = GND, bold values indicate –40°C< TJ < +125°C; unless noted.
Parameter
Conditions
Min
Output Voltage Accuracy
Typ
-2.0
-3.0
Max
Units
+2.0
+3.0
%
%
Output Current Capability
VIN > 1.8V
300
Load Regulation
IOUT = 100µA to 300mA
0.3
1.5
%
Line Regulation
VIN1(2) = VLDO1(2) +1V to 5.5V
0.02
0.3
%/V
Dropout Voltage
IOUT = 300mA @ Vout > 1.5V
142
300
mV
Current Limit
VOUT = 0V
650
900
mA
Ripple Rejection
f = up to 1kHz; COUT = 2.2µF; CBYP = 0.1µF
f = 20kHz; COUT = 2.2µF; CBYP = 0.1µF
70
44
dB
dB
Output Voltage Noise
COUT = 2.2µF; CBYP = 0.1µF; 10Hz to 100KHz
30
µVRMS
350
mA
Electrical Characteristics – LDO3
VIN = DVIN = VEN3 = VLDO3 +1 V; COUT3 = 2.2µF; IOUTLDO3 = 100µA; TJ = 25°C, VEN1 = VEN2 = GND
bold values indicate –40°C< TJ < +125°C; unless noted.
Parameter
Conditions
Min
Output Voltage Accuracy
Typ
-2.0
-3.0
Max
Units
+2.0
+3.0
%
%
0.5
%/V
Line Regulation
VIN = VOUT +1V to 5.5V; IOUT = 100µA
0.03
Load Regulation
IOUT = 100µA to 300mA @ 3.3V
0.50
1.5
%
Dropout Voltage
IOUT = 300mA @ Vin = 2.7V
210
350
mV
Ripple Rejection
f = up to 1kHz; COUT = 2.2µF
f = 20kHz; COUT = 2.2µF
45
20
Current Limit
VOUT = 0V
Output Voltage Noise
COUT = 2.2µF, 10Hz to 100kHz
350
600
470
dB
dB
980
mA
µVRMS
Notes:
1. Exceeding the absolute maximum rating may damage the device.
2. The device is not guaranteed to function outside its operating rating.
3. The maximum allowable power dissipation of any TA (ambient temperature) is PD(max) = (TJ(max) – TA) / θJA. Exceeding the maximum allowable power
dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown.
4. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF.
5. Specification for packaged product only.
April 2008
5
M9999-042208-A
Micrel, Inc.
MIC2811/2821
Typical Characteristics (DC/DC Converter)
Disable
780
760
740
720
700
2.7
2.8
3.4
4.1
4.8
SUPPLY VOLTAGE (V)
5.5
EFFICIENCY (%)
40
30
20
10
0
0
120
80
100
60
-40
60
50
1.2033
1.203
L = 2.2µH
COUT = 2.2µF
1.2027
1.2024
1.2021
1.2018
3.4
4.1
4.8
INPUT VOLTAGE (V)
L = 2.2µH
C = 2.2µF
100 200 300 400 500 600
OUTPUT CURRENT (mA)
Load Regulation
IOUT = 300mA
1.2015
2.7
3.6V
4.2V
5.5
1.205
V = 3.6V
1.2045 IN
L = 2.2µH
1.204 C = 2.2µF
1.2035
1.203
1.2025
1.202
1.2015
1.201
1.2005
1.2
0
100 200 300 400 500 600
OUTPUT CURRENT (mA)
1.5
L = 2.2µH
1.45 C = 2.2µF
CURRENT LIMIT (A)
2
1.8
1.6
April 2008
TEMPERATURE (°C)
80
70
3V
Current Limit
vs. Input Voltage
2.2
3.4
4.1
4.8
INPUT VOLTAGE (V)
1.18
1.2036
Switching Frequency
vs. Input Voltage
IOUT = 300mA
2.6 L = 2.2µH
C = 2.2µF
2.4
1.4
2.7
1.19
OUTPUT VOLTAGE (V)
820
800
= 300mA
1.2
1.2039
Enable
OUTPUT VOLTAGE (V)
ILOAD = 100mA
L = 2.2µH
840 C
= 2.2µF
OUT
OUT
Line Regulation
DC/DC Enable Threshold
vs. Supply Voltage
860
I
1.17
120
100
80
60
40
0
20
-40
ENABLE THRESHOLD (mV)
880
TEMPERATURE (°C)
90
40
2
1.9
1.8
1.21
20
2.2
2.1
100
1.22 C
= 4.7µF
OUT
0
2.4
2.3 IOUT = 300mA
1.2VOUT Efficiency
VIN = 4V
-20
VOUT = 1.2V
1.7
1.6
SWITCHING FREQUENCY (MHz)
1.23
VIN = 4V
-20
FRQUENCY (MHz)
2.5
OUTPUT VOLTAGE (V)
2.6
Output Voltage
vs. Temperature
SW Frequency
vs. Temperature
5.5
1.4
1.35
1.3
1.25
1.2
1.15
1.1
1.05
1
2.7
3.4
4.1
4.8
INPUT VOLTAGE (V)
6
5.5
M9999-042208-A
Micrel, Inc.
MIC2811/2821
Typical Characteristics (LDO)
MIC2811 LDO2 PSRR
10
0
10 1E+2
1k 1E+4
10k 100k
1M
100 1E+3
1E+1
1E+5 1E+6
FREQUENCY (Hz)
MIC2811 LDO1 Output Noise
Spectral Density
MIC2811 LDO2 Output Noise
Spectral Density
0
1k 1E+4
100k 1E+6
10k 1E+5
10 1E+2
100 1E+3
1M
1E+1
FREQUENCY (Hz)
MIC2811 LDO3 Output Noise
Spectral Density
10
10
1
1
1
0.1 VIN = 4V
COUT = 2.2µF
Noise(10Hz to 100kHz) = 46.75µV
2.6 COUT = 2.2µF
2.5
2.45
April 2008
50 100 150 200 250 300
OUTPUT CURRENT (mA)
1.84
-40
120
80
2.53
VIN = 5.5V
2.525
= 150mA
I
1.83 LOAD
C = 2.2µF
1.82
1.81
1.8
1.79
1.78
1.77
1.76
1.75
2
2.5 3 3.5 4 4.5 5 5.5
VIN1 INPUT VOLTAGE (V)
7
TEMPERATURE (°C)
LDO2
Line Regulation
2.52
2.515
ILOAD = 150mA
C = 2.2µF
2.51
2.505
2.5
2.495
2.49
2.485
2.48
2.8
1.76
1.75
0
100
2.55
OUTPUT VOLTAGE (V)
1.78
1.77
2.65
2.35
1.85
OUTPUT VOLTAGE (V)
1.79
2.7
2.6
TEMPERATURE (°C)
IOUT = 150mA
LDO1
Line Regulation
1.85
1.82 C = 2.2µF
1.81
1.8
2.75
2.4
LDO1
Load Regulation
1.84 VIN = 5.5V
1.83 VIN1 = 3.6V
LDO3 OUT (V)
IOUT = 150mA
60
120
80
TEMPERATURE (°C)
100
60
40
20
0
-40
-20
1.76
1.74
VIN = 4V
2.8 COUT = 2.2µF
40
1.78
2.55
20
1.82
1.8
1.72
1.7
2.85
VIN = 4V
-20
COUT = 2.2µF
RMS
1k 10k 100k 1M 10M
FREQUENCY (Hz)
LDO3
vs. Temperature
-20
2.65
VIN = 4V
-40
1.86
1.84
LDO2
vs. Temperature
LDO2 OUT (V)
1.9
0.001
10 100
1k 10k 100k 1M 10M
FREQUENCY (Hz)
120
0.001
10 100
VOUT = 2.7V
Noise(10Hz to 100kHz) = 91.93µV
RMS
5.5
1k 10k 100k 1M 10M
FREQUENCY (Hz)
CBYP = 0.1µF
80
RMS
LDO1
vs. Temperature
1.88
0.01
VOUT = 2.5V
0
0.001
10 100
CBYP = 0.1µF
100
0.01
VOUT = 1.8V
0.1 VIN = 4V
COUT = 2.2µF
5.2
CBYP = 0.1µF
Noise(10Hz to 100kHz) = 35.88µV
LDO1 OUT (V)
10
10
0.01
OUTPUT VOLTAGE (V)
20
010
1k 1E+4
1M
100 1E+3
10k 1E+5
100k 1E+6
1E+1
1E+2
FREQUENCY (Hz)
0.1 VIN = 4V
COUT = 2.2µF
300mA
30
4.9
10
30 300mA
20
40
60
20
40
50
3.1
30
150mA
60
50
4.6
300mA
150mA
60
40
150mA
40
80
70
4.3
50
10mA
70
4.0
60
PSRR (dB)
PSRR (dB)
70
10mA
PSRR (dB)
10mA
80
0
90
20
100
80
3.7
90
MIC2811 LDO3 PSRR
3.4
MIC2811 LDO1 PSRR
VIN2 INPUT VOLTAGE (V)
M9999-042208-A
Micrel, Inc.
MIC2811/2821
Typical Characteristics (LDO cont.)
LDO2 Dropout Voltage
vs. Load Current
2.5025
120 V
= 1.2V
OUT
100 C = 2.2µF
80
60
40
20
0
0
50 100 150 200 250 300
OUTPUT CURRENT (mA)
2.502
2.5005
2.5
2.4995
2.499
2.4985
2.498
2.4975
0
2.704
2.702
2.7
2.698
2.696
2.694
2.692
2.69
0
April 2008
50 100 150 200 250 300
OUTPUT CURRENT (mA)
65
GND CURRENT (µA)
OUTPUT VOLTAGE (mV)
2.71
V = 3.6V
2.708 IN
C = 2.2µF
2.706
2.74
V = 3.6V
2.5015 IN2
C = 2.2µF
2.501
LDO3
Load Regulation
2.75
VIN = 5.5V
OUTPUT VOLTAGE (V)
VIN = 5.5V
OUTPUT VOLTAGE (V)
DROPOUT VOLTAGE (mV)
140
LDO2
Load Regulation
50 100 150 200 250 300
OUTPUT CURRENT (mA)
2.73
2.72
LDO3
Line Regulation
ILOAD = 150mA
C = 2.2µF
2.71
2.7
2.69
2.68
2.67
2.66
2.65
3.1
3.7
4.3
4.9
5.5
VIN3 INPUT VOLTAGE (V)
LDO2 GND Current
vs. Output Current
V = 3.6V
64 IN
C = 2.2µF
63
62
61
60
59
58
57
56
55
0
50 100 150 200 250 300
OUTPUT CURRENT (mA)
8
M9999-042208-A
Micrel, Inc.
MIC2811/2821
Functional Characteristics (DC/DC Converter)
April 2008
9
M9999-042208-A
Micrel, Inc.
MIC2811/2821
Functional Characteristics (LDO)
April 2008
10
M9999-042208-A
Micrel, Inc.
MIC2811/2821
Functional Diagram
DVIN
VIN
P-Channel
Current Limit
6
BIAS
HSD
CBIAS
PWM
Control
SW
VOUT
Anti-Shoot
Through
COUT
LSD
N-Channel
Current Limit
PGND
R1
EN
Bias,
UVLO,
Thermal
Shutdown
Enable and
Control Logic
Internal for
Fixed Output
Options
Connect VOUT
R2
directly to FB
FB
Soft
Start
EA
1.0V
BIAS
EN3
(MIC2821)
LDO
Current
Limit
EA
BIAS
LDO3
VIN1
CLDO3
LDO
Current
Limit
EN1
EA
LDO1
VIN2
CLDO1
LDO
Current
Limit
EN2
EA
LDO2
BIAS
CLDO2
0.8V
LDO1 & 2
Quick Start
Ref Voltage
BYP
750k
0.8V
CBYP
(MIC2811)
SGND
Block Diagram
April 2008
11
M9999-042208-A
Micrel, Inc.
MIC2811/2821
performance. X7R-type capacitors change capacitance
by 15% over their operating temperature range and are
the most stable type of ceramic capacitors. Z5U and
Y5V dielectric capacitors change value by as much as
50% to 60% respectively over their operating
temperature ranges and for that reason are not
recommended. Larger output capacitances can be
achieved by placing tantalum or aluminum electrolytics
in parallel with the ceramic capacitor. For example, a
100µF electrolytic in parallel with a 10µF ceramic can
provide the transient and high frequency noise
performance of a 100µF ceramic at a significantly lower
cost. Specific undershoot/overshoot performance will
depend on both the values and ESR/ESL of the
capacitors.
Applications Information
The MIC2811 and MIC2821 are power management ICs
with a single integrated step-down regulator and three
low dropout regulators. LDO1, LDO2, and LDO3 are
300mA low dropout regulators supplied by their own
independent input voltage pins. The supply to LDO3
(VIN) also powers the bias circuitry and must be available
for any output to be operational. This supply requires an
external connection to DVIN. The step-down regulator is
a 2MHz 600mA PWM power supply, using small values
of L and C operating at over 90% efficiency.
DVIN/VIN/VIN1/VIN2
All four regulators, the switch mode regulator, LDO1,
LDO2, and LDO3 have their own unique input voltage
supply pin. VIN provides power to LDO3 and internal
circuitry shared by all the regulators and therefore must
be available for any of the regulators to operate properly.
DVIN and VIN must be tied together and have a
minimum input voltage of 2.7V. Inputs to LDO1 (VIN1)
and LDO2 (VIN2) can go as low as 1.65V, but should
never exceed the VIN and DVIN input voltage. Due to
the high switching speeds, a 1µF input capacitor is
recommended close to the DVIN, decoupled to the
PGND pin.
Inductor Selection
Inductor selection will be determined by the following
(not necessarily in the order of importance);
• Inductance
• Rated current value
• Size requirements
• DC resistance (DCR)
The MIC2811 and MIC2821 are designed for use with a
2.2µH inductor. 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 that the peak current will not saturate the
inductor. Peak inductor current can be calculated as
follows:
LDO1
Regulated output voltage of LDO1. Power is provided by
VIN1 and enabled through EN1. Recommended output
capacitance is 2.2µF, decoupled to the SGND pin.
LDO2
Regulated output voltage of LDO2. Power is provided by
VIN2 and enabled through EN2. Recommended output
capacitance is 2.2µF, decoupled to the SGND pin.
I PK = IOUT +
LDO3
Regulated output voltage of LDO3. Power is provided by
VIN and enabled through EN (MIC2811) or EN3
(MIC2821). Recommended output capacitance is 2.2µF,
decoupled to the SGND pin.
VOUT
VIN
)
2×f ×L
The size requirements refer to the area and height
requirements that are necessary to fit a particular
design. Please refer to the inductor dimensions on their
datasheet.
DC resistance is also important. While DCR is inversely
proportional to size, DCR can represent a significant
efficiency loss.
SW
The switch (SW) pin connects directly to the inductor
and provides the switching current necessary to operate
in PWM mode. Due to the high speed switching on this
pin, the switch node should be routed away from
sensitive nodes.
Efficiency Considerations
Efficiency is defined as the amount of useful output
power, divided by the amount of power supplied.
DC/DC Output Capacitor
The DC/DC regulator requires an output capacitor for
proper operation. Values of greater than 2.2µF improve
transient response and noise reduction at high
frequency. X7R/X5R dielectric-type ceramic capacitors
are recommended because of their superior temperature
April 2008
VOUT (1 −
⎛ Vout × Iout ⎞
Efficiency _ % = ⎜
⎟ × 100
⎝ Vin × Iin ⎠
Maintaining high efficiency serves two purposes. It
reduces power dissipation in the power supply, reducing
the need for heat sinks and thermal design
12
M9999-042208-A
Micrel, Inc.
MIC2811/2821
considerations and it reduces consumption of current for
battery powered applications. Reduced current draw
from a battery increases the devices operating time and
is critical in hand held devices.
There are two types of losses in switching converters;
DC losses and switching losses. DC losses are simply
the power dissipation of I2R. 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
Current2. 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
is another DC loss.
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, 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
follows:
MIC2811 Layout Recommendations
A poor layout of the MIC2811 may cause unwanted
voltage and current spikes. This can lead to noise on DC
voltages and EMI radiating to nearby devices. The
following are recommendations for the MIC2811/21
layout. The evaluation board layout is included as an
example.
1. Place the MIC2811/21 with the pad size designated
in the “Recommended Land Patterns” page of the Micrel
website.
2. When laying out the components, keep the MIC2811,
inductor, and filter capacitors physically close to keep
traces as short as possible. The traces between these
components carry relatively high switching currents and
can affect adjacent signals.
3. The input capacitor between DVIN and PGND should
be placed right next to the MIC2811/21. This will
eliminate trace inductance effects and reduce internal
noise for the MIC2811/21 control circuitry. The trace
from the DVIN filter capacitor to the MIC2811/21 device
should not be routed through any vias. This lessens the
chance of noise coupling by the effective antenna of the
via.
4. Monitoring the path of the switching currents will help
minimize the radiated noise. In the first half of the
switching cycle, current flows from the input filter
capacitor through the high side switch within the
MIC2811, then through the inductor to the output filter
capacitor and lastly through ground. In the second half of
the switching cycle, current is pulled up from ground
through the low side synchronous switch within the
MIC2807 by the inductor, to the output filter capacitor
and then back through ground, forming a second current
loop. Route these loops to ensure the current curls in the
same direction, preventing magnetic field reversal
between the switching cycles.
5. Connect the Bypass capacitor (MIC2811 Only) to the
BYP pin and the AGND pin. AGND and PGND should be
connected close to the chip at a single point in order to
minimize undesirable behavior due to ground bounce.
Input and output filter capacitors should be connected to
PGND.
6. Connections between power components and the
MIC2811 should have wide traces. It is good practice to
use a minimum of 30mils (0.762mm) per Ampere for 1oz
copper weight.
7. Route noise sensitive traces such as Feedback (FB),
BIAS, and BYP away from the switching traces and the
inductor. Noise coupled into these pins can affect the
accuracy of the output. The Feedback pin should be
connected at point of load for an accurate load
regulation.
L _ Pd = Iout 2 × DCR
From that, the loss in efficiency due to inductor
resistance can be calculated as follows;
⎡ ⎛
⎞⎤
Vout × Iout
⎟⎟⎥ × 100
Efficiency _ Loss = ⎢1 − ⎜⎜
⎣ ⎝ Vout × Iout + L _ Pd ⎠⎦
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.
PGND
Power ground (PGND) is the ground path for the high
current PWM mode. The current loop area for the power
ground should be as small as possible.
SGND
Signal ground (SGND) is the ground path for the biasing
and control circuitry. The current loop for the signal
ground should be as small as possible.
BYP (MIC2811 only)
For enhanced noise and PSRR performance on LDO1 &
LDO2, the internal reference of the MIC2811 can be
bypassed with a capacitor to ground. A quick-start
feature allows for quick turn-on of the output voltage.
The recommended nominal bypass capacitor is 0.1µF,
but it can be increased, which will also result in an
increase to the start-up time.
April 2008
13
M9999-042208-A
Micrel, Inc.
MIC2811/2821
MIC2811/2821-YML Schematic
J1
DVIN
U1
MIC2811/2821-YML
DVIN
6
C1
4.7µF/6.3V
J2
GND
DVIN
VO-LDO2
LDO2
10
VIN
12
VIN1
C2
4.7µF/6.3V
J4
VIN2
VIN1
C3
4.7µF/6.3V
C4
VIN2
4.7µF/6.3V
LDO1
J6
EN
R5
SGND
PGND
EN2
J12
VO_LDO1
J5
GND
VO
J13
VOUT
C10
4.7µF/6.3V
R2
OPTION
3
EN1
16
BYP/EN3
1
J11
VO_LDO2
J14
GND
13
EN
4
J7
EN1
15
J10
VO_LDO3
2.2µH
R1
OPTION
FB
J6
EN
L1
5
VIN2
14
J8
EN2
R4
10K
R5
10K
11
C7
2.2µF/6.3V
SW
7
8
C8
2.2µF/6.3V
VIN1
VIN2
9
C9
2.2µF/6.3V
DVIN
J3
VIN1
VO-LDO3
LDO3
BIAS
2
C6
0.1µF/10V
10K (FOR MIC2821 ONLY)
C5
0.1µF (FOR MIC2811 ONLY)
April 2008
14
M9999-042208-A
Micrel, Inc.
MIC2811/2821
Bill of Materials
Item
Part Number
C5, C6
JMK107BJ475MA-T
Taiyo Yuden
C1608X5R0J475K
TDK
GRM188R60J475KE19D
muRATA
C1608X5R0J225K
TDK
06036D225KAT2A
AVX
GRM188R60J225KE19D
muRata
VJ0603G225KXYAT
Vishay
C1005X7R1A104K
TDK
R1
(3)
2.2µF, 6.3V, 0603, X5R Ceramic Capacitor
3
0.1µF, 10V, X5R Ceramic Capacitor
(C5 for MIC2811 EV Board only)
2
(1)
(2)
(4)
(3)
(4)
CDRH2D11HPNP
Sumida
(6)
2.2µH, 1.1A, 3.2x3.2x1.2mm Inductor
(7)
2.2µH, 1.1A, 2.5x3.2x2mm Inductor
ME3220-222-ML
Coilcraft
CRCW06030R00FRT1
Vishay
CRCW06031002FRT1
Vishay
MIC2811/21
5
(3)
Vishay
U1
4.7µF, 6.3V, 0603, X5R Ceramic Capacitor
(2)
1
(4)
0Ω, 0603, 1% resistor
1
Open
0
(4)
10kΩ, 0603, 1% resistor
R2
R3, R4, R5
Qty.
(5)
VJ0603Y104KXQCW1BC
L1
Description
(1)
AVX
C1, C2, C3,
C4, C10
C7, C8, C9
Manufacturer
06036D475KAT2A
Micrel, Inc.
(8)
16-Pin 3mm x 3mm MLF
3
®
1
Notes:
1. AVX: www.avx.com
2. Murata: www.murata.com
3. TDK: www.tdk.com
4. Vishay: www.vishay.com
5. Taiyo Yuden: www.t-yuden.com
6. Sumida: www.sumida.com
7. Coilcraft: www.coilcraft.com
8. Micrel, Inc.: www.micrel.com
April 2008
15
M9999-042208-A
Micrel, Inc.
MIC2811/2821
PCB Layout Recommendations
Top Layer
Bottom Layer
April 2008
16
M9999-042208-A
Micrel, Inc.
MIC2811/2821
Package Information
16-Pin 3mm x 3mm MLF® (ML)
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.
© 2008 Micrel, Incorporated.
April 2008
17
M9999-042208-A
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