MIC2194
Micrel
MIC2194
400kHz SO-8 Buck Control IC
General Description
Micrel’s MIC2194 is a high efficiency PWM buck control IC
housed in the SO-8 package. Its 2.9V to 14V input voltage
range allows it to efficiently step down voltages in 3.3V, 5V,
and 12V systems as well as 1- or 2-cell Li Ion battery powered
applications. The flexible architecture of the MIC2194 allows
for it to be configured as a buck or a buck-boost converter.
The MIC2194 solution saves valuable board space. The
device is housed in the space-saving SO-8 package, whose
low pin-count minimizes external components. Its 400kHz
PWM operation allows a small inductor and small output
capacitors to be used. The MIC2194 can implement all-
ceramic capacitor solutions.
The MIC2194 drives a high-side P-channel MOSFET. A low
output driver impedance of 2Ω allows the MIC2194 to drive
large external MOSFETs to generate a wide range of output
currents. The MIC2194 can achieve maximum duty cycles of
100%, which can be useful in low headroom applications.
The MIC2194 is available in an 8 pin SOIC package with a
junction temperature range of –40°C to +125°C.
Features
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2.9V to 14V input voltage range
400kHz oscillator frequency
PWM current mode control
2Ω output drivers
100% maximum duty cycle
0.5µA micro-power shutdown
Programmable UVLO
Front edge blanking
Cycle-by-cycle current limiting
Frequency foldback short circuit protection
8-lead SOIC package
Point of load power supplies
Negative voltage buck-boost power supplies
Distributed power systems
Base stations
Wireless modems
ADSL line cards
Servers
Step down conversion in 3.3V, 5V, 12V systems
1-and 2-cell Li Ion battery operated equipment
Applications
Typical Application
V
IN
12V
47µF
20V
(×2)
0.012Ω
MIC2194BM
VIN
CS
EN/ OUTP
UVLO
VDD
FB
2k
2.2nF
COMP GND
3.32k
Si4431A
(×2)
5.2µH
B530 10k
220µF
10V
(×2)
V
OUT
5V, 5A
1µF
Adjustable Output Buck Converter
V
IN
+3.3V
10µF
16V
0.040Ω
MIC2194BM
VIN
CS
EN/ OUTP
UVLO
VDD
FB
4.99k COMP
GND
10nF
V
OUT
–5V, 0.6A
B530
3.01k
1k
22nF
220µF
10V
(×2)
Si9803
22µH
10µF
16V
1µF
Positive-to-Negative Buck-Boost Converter
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 2005
1
MIC2194
MIC2194
Micrel
Ordering Information
Part Number
Standard
MIC2194BM
Lead-Free
MIC2194YM
Output Voltage
Adjustable
Frequency
400kHz
Junction Temp. Range
–40°C to +125°C
Package
8-lead SOP
Pin Configuration
COMP 1
FB 2
EN/UVLO 3
CS 4
8 VIN
7 OUTP
6 GND
5 VDD
8 Lead SOIC (M)
Pin Description
Pin Number
1
2
3
Pin Name
COMP
FB
EN/UVLO
Pin Function
Compensation (Output): Internal error amplifier output. Connect to a
capacitor or series RC network to compensate the regulator’s control loop.
Feedback (Input): The circuit regulates this pin to 1.245V.
Enable/Undervoltage Lockout (Input): A low level on this pin will power down
the device, reducing the quiescent current to under 0.5µA. This pin has two
separate thresholds, below 1.5V the output switching is disabled, and below
0.9V the device is forced into a complete micropower shutdown. The 1.5V
threshold functions as an accurate undervoltage lockout (UVLO) with
hysteresis.
The (–) input to the current limit comparator. A built-in offset of 110mV
between VIN and CSL in conjunction with the current sense resistor sets the
current limit threshold level. This is also the (–) input to the current amplifier.
3V internal linear-regulator output. VDD is also the supply voltage bus for the
chip. Bypass to GND with 1µF.
Ground.
High current drive for the synchronous N-channel MOSFET. Voltage swing
is from ground to VIN. On-resistance is typically 3Ω @ 5V
IN
.
Input voltage to the circuit. Also the high side input to the current sense
amplifier supplies power to the gate drive circuit.
4
CS
5
6
7
8
VDD
GND
OUTP
VIN
MIC2194
2
April 2005
MIC2194
Micrel
Absolute Maximum Ratings
(Note 1)
Supply Voltage (V
IN
) ..................................................... 15V
Digital Supply Voltage (V
DD
) ........................................... 7V
Enable Pin Voltage (V
EN
) ............................. –0.3V to +15V
Comp Pin Voltage (V
COMP
) ............................ –0.3V to +3V
Feedback Pin Voltage (V
FB
) .......................... –0.3V to +3V
Current Sense Voltage (V
IN
–V
CS
) ................. –0.3V to +1V
Power Dissipation (P
D
) ..................... 285mW @ T
A
= 85°C
Ambient Storage Temp ............................ –65°C to +150°C
ESD Rating,
Note 3 ......................................................
2kV
Operating Ratings
(Note 2)
Supply Voltage (V
IN
) .................................... +2.9V to +14V
Junction Temperature ....................... –40°C
≤
T
J
≤
+125°C
Package Thermal Resistance
θ
JA
8-lead SOP ................................................. 140°C/W
Electrical Characteristics
V
IN
= 5V, V
OUT
= 3.3V, T
J
= 25°C, unless otherwise specified.
Bold
values indicate –40°C<T
J
<+125°C.
Parameter
Regulation
Feedback Voltage Reference
Feedback Bias Current
Output Voltage Line Regulation
Output Voltage Load Regulation
Output Voltage Total Regulation
Input & V
DD
Supply
V
IN
Input Current (I
Q
)
Shutdown Current (I
SD
)
Digital Supply Voltage (V
DD
)
Digital Supply Load Regulation
Undervoltage Lockout
UVLO Hysteresis
Enable/UVLO
Enable Input Threshold
UVLO Threshold
Enable Input Current
Current Limit
Current Limit Threshold Voltage
Error Amplifier
Error Amplifier Gain
Current Amplifier
Current Amplifier Gain
Oscillator Section
Oscillator Frequency (f
O
)
Maximum Duty Cycle
Minimum On Time
Frequency Foldback Threshold
Frequency Foldback Frequency
V
FB
= 1.0V
V
FB
= 1.5V
Measured on FB
360
100
165
0.3
90
400
440
kHz
%
ns
V
kHz
3.0
V/V
20
V/V
V
IN
– V
CS
voltage to trip current limit
90
110
130
mV
V
EN/UVLO
= 5V
0.6
1.4
0.9
1.5
0.2
1.2
1.6
5
V
V
µA
(excluding external MOSFET gate current)
V
EN
= 0V
I
L
= 0
I
L
= 0 to 1mA
V
DD
upper threshold (turn on threshold)
2.82
1
0.5
3.0
0.1
2.65
100
2
5
3.18
mA
µA
V
V
V
mV
5V
≤
V
IN
≤
9V
0mV < (V
IN
– V
CS
) < 75mV
5V
≤V
IN
≤
9V, 0mV < (V
IN
– V
CS
) < 75mV (±3%)
1.208
(1%)
(2%)
1.233
1.22
1.245
1.245
50
0.15
0.9
1.282
1.257
1.27
V
V
nA
%/V
%
V
Condition
Min
Typ
Max
Units
April 2005
3
MIC2194
MIC2194
Parameter
Gate Drivers
Rise/Fall Time
Output Driver Impedance
C
L
= 3300pF
Source, V
IN
= 12V
Sink, V
IN
= 12V
Source, V
IN
= 5V
Sink, V
IN
= 5V
25
2
2
3
3
6
6
7
7
Condition
Min
Typ
Max
Micrel
Units
ns
Ω
Ω
Ω
Ω
Note 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 device is not guaranteed to function outside its operating rating.
Devices are ESD sensitive, handling precautions required. Human body model, 1.5kΩ in series with 100pF.
Note 2.
Note 3.
MIC2194
4
April 2005
MIC2194
Micrel
Typical Characteristics
Quiescent Current
vs. Input Voltage
4.5
QUIESCENT CURRENT (mA)
4
3.5
3
2.5
2
1.5
1
0.5
0
0
Standby
5
10
INPUT VOLTAGE (V)
15
Switching
QUIESCENT CURRENT (mA)
Quiescent Current
vs. Temperature
2.0
1.8
1.6
1.4
V
DD
(V)
V
IN
= 5V
3.05
3.00
2.95
2.90
2.85
2.80
0
V
DD
vs. Input Voltage
1.2
1.0
0.8
0.6
0.4
0.2
0
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
5
10
INPUT VOLTAGE (V)
15
REFERENCE VOLTAGE (V)
3.05
3.03 V
IN
= 3.3V
3.01
2.99
V
DD
vs. Load
3.50
3.40
3.30
3.20
VDD (V)
V
DD
vs. Temperature
Error Amp Reference Voltage
vs. Input Voltage
1.2455
1.2450
1.2445
1.2440
1.2435
1.2430
0
V
DD
(V)
2.97
2.95
2.93
2.91
2.89
2.87
2.85
0
V
IN
= 5V
3.10
3.00
2.90
2.80
2.70
2.60
V
IN
= 5V
V
IN
= 12V
0.2 0.4 0.6 0.8
1
1.2
V
DD
LOAD CURRENT (mA)
2.50
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
2
4 6 8 10 12 14
INPUT VOLTAGE (V)
Error Amp Reference Voltage
vs. Temperature
1.3
FREQUENCY VARIATION (%)
0.5
Frequency Variation
vs. Input Voltage
450
SOFT START CURRENT (µA)
440
430
420
410
400
390
380
370
Frequency Variation vs.
Temperature
V
IN
= 5V
REFERENCE VOLTAGE (V)
1.29
1.28
1.27
1.26
1.25
1.24
1.23
1.22
1.21 V
IN
= 5V
1.2
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
0
-0.5
-1
-1.5
-2
0
2
4
6
8 10 12
INPUT VOLTAGE (V)
14
360
350
-50 -30 -10 10 30 50 70 90 110
TEMPERATURE (°C)
Overcurrent Threshold vs.
Input Voltage
130
125
CURRENT LIMIT (mV)
120
115
110
105
100
95
90
85
2
4 6 8 10 12 14
INPUT VOLTAGE (V)
Current Limit Threshold
vs. Temperature
4.5
V
IN
= 5V
IMPEDANCE (Ω)
4
3.5
3
2.5
2
1.5
1
0.5
0
0
OUTP Drive Impedance
vs. Input Voltage
THRESHOLD (mV)
120
115
110
105
100
95
90
0
Source(Ω)
Sink (Ω)
80
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
2
4 6 8 10 12 14
INPUT VOLTAGE (V)
April 2005
5
MIC2194
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