MIC2168
Micrel
MIC2168
1MHz PWM Synchronous Buck Control IC
General Description
The MIC2168 is a high-efficiency, simple to use 1MHz PWM
synchronous buck control IC housed in a small MSOP-10
package. The MIC2168 allows compact DC/DC solutions
with a minimal external component count and cost.
The MIC2168 operates from a 3V to 14.5V input, without the
need of any additional bias voltage. The output voltage can
be precisely regulated down to 0.8V. The adaptive all
N-Channel MOSFET drive scheme allows efficiencies over
95% across a wide load range.
The MIC2168 senses current across the high-side N-Chan-
nel MOSFET, eliminating the need for an expensive and
lossy current-sense resistor. Current limit accuracy is main-
tained by a positive temperature coefficient that tracks the
increasing R
DS(ON)
of the external MOSFET. Further cost
and space are saved by the internal in-rush-current limiting
digital soft-start.
The MIC2168 is available in a 10-pin MSOP package, with a
wide junction operating range of –40°C to +125°C.
All support documentation can be found on Micrel’s web
site at www.micrel.com.
Features
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3V to 14.5V input voltage range
Adjustable output voltage down to 0.8V
Up to 95% efficiency
1MHz PWM operation
Adjustable current-limit senses high-side N-Channel
MOSFET current
No external current sense resistor
Adaptive gate drive increases efficiency
Ultra-fast response with hysteretic transient recovery
mode
Overvoltage protection protects the load in fault
conditions
Dual mode current limit speeds up recovery time
Hiccup mode short-circuit protection
Internal soft-start
Dual function COMP and EN pin allows low-power
shutdown
Small size MSOP 10-lead package
Point-of-load DC/DC conversion
Set-top boxes
Graphic cards
LCD power supplies
Telecom power supplies
Networking power supplies
Cable modems and routers
Applications
Typical Application
V
IN
= 5V
SD103BWS
100µF
4.7µF
100
95
90
EFFICIENCY (%)
0.1µF
MIC2168 Efficiency
VDD
BST
CS
HSD
VSW
1kΩ
IRF7821
1.2µH
3.3V
10kΩ
150µF x 2
3.24kΩ
85
80
75
70
65
60
55
50
V
IN
= 5V
V
OUT
= 3.3V
0
2
4
6
I
LOAD
(A)
8
10
VIN
MIC2168
COMP/EN
100pF
4kΩ
100nF
GND
LSD
FB
IRF7821
MIC2168 Adjustable Output 1MHz Converter
Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com
November 2003
1
M9999-111803
MIC2168
Micrel
Ordering Information
Part Number
MIC2168BMM
Frequency
1MHz
Junction Temp. Range
–40°C to +125°C
Package
10-lead MSOP
Pin Configuration
VIN
VDD
CS
COMP/EN
FB
1
2
3
4
5
10
9
8
7
6
BST
HSD
VSW
LSD
GND
10-Pin MSOP (MM)
Pin Description
Pin Number
1
2
Pin Name
VIN
VDD
Pin Function
Supply Voltage (Input): 3V to 14.5V.
5V Internal Linear Regulator (Output): V
DD
is the external MOSFET gate
drive supply voltage and an internal supply bus for the IC. When V
IN
is <5V,
this regulator operates in dropout mode.
Current Sense / Enable (Input): Current-limit comparator noninverting input.
The current limit is sensed across the MOSFET during the ON time. The
current can be set by the resistor in series with the CS pin.
Compensation (Input): Dual function pin. Pin for external compensation. If
this pin is pulled below 0.2V, with the reference fully up the device shuts
down (50µA typical current draw).
Feedback (Input): Input to error amplifier. Regulates error amplifier to 0.8V.
Ground (Return).
Low-Side Drive (Output): High-current driver output for external synchro-
nous MOSFET.
Switch (Return): High-side MOSFET driver return.
High-Side Drive (Output): High-current output-driver for the high-side
MOSFET. When V
IN
is between 3.0V to 5V, 2.5V threshold-rated MOSFETs
should be used. At V
IN
> 5V, 5V threshold MOSFETs should be used.
Boost (Input): Provides the drive voltage for the high-side MOSFET driver.
The gate-drive voltage is higher than the source voltage by V
IN
minus a
diode drop.
3
CS
4
COMP/EN
5
6
7
8
9
FB
GND
LSD
VSW
HSD
10
BST
M9999-111803
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November 2003
MIC2168
Micrel
Absolute Maximum Ratings
(1)
Supply Voltage (V
IN
) .................................................. 15.5V
Booststrapped Voltage (V
BST
) ............................... V
IN
+5V
Junction Temperature (T
J
) ................. –40°C
≤
T
J
≤+125°C
Storage Temperature (T
S
) ....................... –65°C to +150°C
Operating Ratings
(2)
Supply Voltage (V
IN
) .................................... +3V to +14.5V
Output Voltage Range ........................... 0.8V to V
IN
×
D
MAX
Package Thermal Resistance
θ
JA
10-lead MSOP ............................................ 180°C/W
Electrical Characteristics
(3)
T
J
= 25°C, V
IN
= 5V, unless otherwise specified.
Bold
values indicate –40°C < T
J
< +125°C
Parameter
Feedback Voltage Reference
Feedback Voltage Reference
Feedback Bias Current
Output Voltage Line Regulation
Output Voltage Load Regulation
Output Voltage Total Regulation
Oscillator Section
Oscillator Frequency
Maximum Duty Cycle
Minimum On-Time
(4)
Input and V
DD
Supply
PWM Mode Supply Current
Shutdown Quiescent Current
V
COMP
Shutdown Threshold
V
COMP
Shutdown Blanking
Period
Digital Supply Voltage (V
DD
)
Notes:
1. Absolute maximum ratings indicate limits beyond which damage to the component may occur. Electrical specifications do not apply when operating
the device outside of its operating ratings. The maximum allowable power dissipation is a function of the maximum junction temperature, T
J
(max),
the junction-to-ambient thermal resistance,
θ
JA
, and the ambient temperature, T
A
. The maximum allowable power dissipation will result in excessive
die temperature, and the regulator will go into thermal shutdown.
2. Devices are ESD sensitive, handling precautions required.
3. Specification for packaged product only.
4. Guaranteed by design.
Condition
(± 1%)
(± 2% over temp)
Min
0.792
0.784
Typ
0.8
0.8
30
0.03
0.5
Max
0.808
0.816
100
Units
V
V
nA
%/V
%
%
3V
≤
V
IN
≤
14.5V; 1A
≤
I
OUT
≤
10A; (V
OUT
= 2.5V)
(4)
900
90
0.6
1000
1100
kHz
%
30
60
ns
V
CS
= V
IN
–0.25V; V
FB
= 0.7V (output switching but excluding
external MOSFET gate current.)
V
COMP/EN
= 0V
0.1
C
COMP
= 100nF
V
IN
≥
6V
4.7
1.6
50
0.25
4
5
3
150
0.4
mA
µA
V
ms
5.3
V
November 2003
3
M9999-111803
MIC2168
Micrel
Electrical Characteristics
(5)
Parameter
Error Amplifier
DC Gain
Transconductance
Soft-Start
Soft-Start Current
Current Sense
CS Over Current Trip Point
Temperature Coefficient
Output Fault Correction Thresholds
Upper Threshold, V
FB_OVT
Lower Threshold, V
FB_UVT
Gate Drivers
Rise/Fall Time
Output Driver Impedance
Into 3000pF at V
IN
> 5V
Source, V
IN
= 5V
Sink, V
IN
= 5V
Source, V
IN
= 3V
Sink, V
IN
= 3V
Driver Non-Overlap Time
Notes:
5. Specification for packaged product only.
6. Guaranteed by design.
Condition
Min
Typ
Max
Units
70
1
dB
ms
µA
µA
ppm/°C
After timeout of internal timer. See
“Soft-Start”
section.
8.5
V
CS
= V
IN
–0.25V
160
200
+1800
240
(relative to V
FB
)
(relative to V
FB
)
+3
–3
%
%
30
6
6
10
10
10
20
ns
Ω
Ω
Ω
Ω
ns
Note 6
M9999-111803
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November 2003
MIC2168
Micrel
Typical Characteristics
V
IN
= 5V
PWM Mode Supply Current
vs. Temperature
PWM Mode Supply Current
vs. Supply Voltage
2.9
2.7
2.5
2.3
2.1
1.9
1.7
1.5
1.3
1.1
0.9
0.7
0.5
-40 -20 0 20 40 60 80 100120140
TEMPERATURE (°C)
2.0
QUIESCENT CURRENT (mA)
0.820
0.815
0.810
V
FB
Line Regulation
1.5
I
DD
(mA)
V
FB
(V)
1.0
0.5
0.805
0.800
0.795
0.790
0.785
0
5
10
SUPPLY VOLTAGE (V)
15
0.780
0
5
V
IN
(V)
10
15
V
FB
vs. Temperature
0.820
0.815
0.810
V
FB
(V)
V
DD
Line Regulation
V
DD
REGULATOR VOLTAGE (V)
6
5
4
5.01
4.99
4.97
4.95
4.93
4.91
4.89
4.87
4.85
0
V
DD
Load Regulation
0.800
0.795
0.790
0.785
0.780
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
V
DD
(V)
0.805
3
2
1
0
0
5
V
IN
(V)
10
15
5
10 15 20 25
LOAD CURRENT (mA)
30
5.0
V
DD
LINE REGULATION (%)
V
DD
Line Regulation
vs. Temperature
1200
1150
FREQUENCY (kHz)
Oscillator Frequency
vs. Temperature
1.5
FREQUENCY VARIATION (%)
Oscillator Frequency
vs. Supply Voltage
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
1.0
0.5
0
-0.5
-1.0
-1.5
0
5
10
SUPPLY VOLTAGE (V)
15
1100
1050
1000
950
900
850
800
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
4
Current Limit Foldback
240
220
Overcurrent Trip Point
vs. Temperature
3
V
OUT
(V)
I
CS
(µA)
200
180
160
140
120
2
1
Top MOSFET = Si4800
R
CS
= 1kΩ
0
0
2
4
6
I
LOAD
(A)
8
10
100
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
November 2003
5
M9999-111803
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