MIC2004/2014
Fixed Current Limit
Power Distribution Switch
Kickstart is a trademark of Micrel, Inc
MLF and
Micro
LeadFrame are 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
General Description
MIC2004 and MIC2014 are current limiting, high-side
power switches, designed for general purpose power
distribution and control in PCs, PDAs, printers and other
self-powered systems.
MIC2004 and MIC2014's primary functions are current
limiting and power switching. They are thermally
protected and will shutdown should their internal
temperature reach unsafe levels, protecting both the
device and the load, under high current or fault
conditions. MIC2004/2014 feature a load discharge FET
which ensures any output capacitance is discharged
when the switch is turned off. This is particularly useful
in hot-swapping applications where `cold' connections
are desired.
Both devices are fully self-contained, with the current
limit value being factory set to one of several convenient
levels.
MIC2014 offers a unique new feature: Kickstart
TM
,
which allows momentary high current surges to pass
unrestricted without sacrificing overall system safety.
MIC2004 and MIC2014 are excellent choices for USB
and IEEE 1394 (FireWire) applications or for any system
where current limiting and power control are desired.
The MIC2004 and MIC2014 are offered in space saving
6 pin SOT-23 and 2mm x 2mm MLF packages.
Data sheets and support documentation can be found
on Micrel's web site at www.micrel.com.
Features
70m typical on-resistance
2.5V - 5.5V operating range
Pre-set current limit values; 0.5A, 0.8A and 1.2A
Load discharge FET
Kickstart
TM
Thermal Protection
Under voltage lock-out
Low quiescent current
Applications
USB / IEEE 1394 Power Distribution
Desktop and Laptop PCs
Set top boxes
Game
consoles
PDAs
Printers
Docking stations
Chargers
_________________________________________________________________________________________________________
Typical Application
VIN
D+/D-
D+/D-
5V Supply
VOUT
GND
ENABLE
MIC2004
MIC2014
USB
Controller
V
BUS
V
BUS
USB
Port
USB
Port
Figure 1. Typical Application Circuit
August 2005
M9999-080305
(408) 955-1690
Micrel
MIC2004/MIC2014
August 2005
2
M9999-080305
(408) 955-1690
MIC2000 Family Members
Part Number
Pin Function
Normal Limiting
Kickstart
I Limit
I Adj.
Enable
C
SLEW
FAULT/ DLM*
Load
Discharge
2003 2013
--
--
--
--
--
--
2004 2014
--
-- -- --
2005 2015
--
-- --
2006 2016
Fixed
--
-- --
2007 2017
-- --
2008 2018
-- -- --
2009 2019
Adj.
-- -- --
* Dynamic Load Management Adj = Adjustable current limit
Fixed = Factory programmed current limit
Ordering Information
Part Number
Marking
(1)
Current Limit
Kickstart
Pb-Free
Package
MIC2004-0.5YM5
FE05
0.5A
MIC2004-0.8YM5
FE08
0.8A
MIC2004-1.2YM5
FE12
1.2A
SOT-23-5
MIC2004-0.5YML
(2)
E05
0.5A
MIC2004-0.8YML
(2)
E08
0.8A
MIC2004-1.2YML
(2)
E12
1.2A
No
2mmX2mm MLF
MIC2014-0.5YM5
FM05
0.5A
MIC2014-0.8YM5
FM08
0.8A
MIC2014-1.2YM5
FM12
1.2A
SOT-23-5
MIC2014-0.5YML
(2)
M05
0.5A
MIC2014-0.8YML
(2)
M09
0.8A
MIC2014-1.2YML
(2)
M12
1.2A
Yes
Yes
2mmX2mm MLF
Note:
1. Under-bar symbol ( _ ) may not be to scale
2. Contact factory for availability.
Micrel
MIC2004/MIC2014
August 2005
3
M9999-080305
(408) 955-1690
Pin Configuration
N
O
D
A
P
E
D
I
S
K
C
A
B
D
N
U
O
R
G
S
I
V
OUT
1
2
3
4
5
6
NIC
NIC
V
IN
GND
ENABLE
6-Lead 2mmX2mm MLF (ML)
Top View
ENABLE
GND
NIC
V
OUT
V
IN
3
1
5
2
4
SOT 23-5 (M5)
Top View
Pin Description
Pin
Number
SOT-23
Pin
Number
MLF
Pin
Name
Type Description
1 6
VIN
Input
Supply input. This pin provides power to both the output switch and the
MIC2004/2014's internal control circuitry.
2 5
GND
--
Ground.
3 4
ENABLE
Input
Output enable pin. A logic HIGH activates the output switch, applying power to
the load attached to V
OUT
.
4 3
NIC
--
No internal connection. An electrical signal to this pin will have no effect on
device operation.
2
NIC
--
No internal connection. An electrical signal to this pin will have no effect on
device operation.
5 1
VOUT
Output
Switch output. The load being driven by MIC2004/2014 is connected to this
pin.
Micrel
MIC2004/MIC2014
August 2005
4
M9999-080305
(408) 955-1690
Absolute Maximum Ratings
(1)
V
IN
, V
OUT
............................................................ 0.3 to 6V
All other pins.................................................. 0.3 to 5.5V
Power Dissipation.................................. Internally Limited
Continuous Output Current..................................... 2.25A
Maximum Junction Temperature........................... 150
C
Storage Temperature .............................. 65
C to 150C
Operating Ratings
(2)
Supply Voltage............................................. 2.5V to 5.5V
Continuous Output Current Range .................... 0 to 2.1A
Ambient Temperature Range ....................40
C to 85C
Package Thermal Resistance (
JA
)
SOT-23-5
.............................................
230C/W
MLF 2x2 mm............................................ 90C/W
MLF 2x2 mm
JC
(5)
.................................. 45C/W
Electrical Characteristics
V
IN
= 5V, T
AMBIENT
= 25
C unless specified otherwise. Bold indicates 40C to +85C limits.
Symbol Parameter
Conditions
Min
Typ
Max
Units
V
IN
Switch Input Voltage
2.5
5.5
V
I
IN
Internal Supply Current
Switch = OFF,
ENABLE = 0V
1 5
A
I
IN
Internal Supply Current
Switch = ON, I
OUT
= 0
ENABLE = 1.5V
80
330
A
I
LEAK
Output Leakage Current
V
IN
= 5V, V
OUT
= 0 V,
ENABLE = 0
12
100
A
70
100
m
R
DS(ON)
Power Switch Resistance
V
IN
= 5V, I
OUT
= 100 mA
125
m
R
DSCHG
Load Discharge Resistance
V
IN
= 5V, I
SINK
= 5 mA
70
126
200
I
LIMIT
Current Limit: 0.5
V
OUT
= 0.8V
IN
0.5
0.7 0.9 A
I
LIMIT
Current Limit: 0.8
V
OUT
= 0.8V
IN
0.8
1.1 1.5 A
I
LIMIT
Current Limit: 1.2
V
OUT
= 0.8V
IN
1.2
1.6 2.1 A
I
LIMIT_2nd
Secondary current limit
(Kickstart)
MIC2014, V
IN
= 2.5V
2.2
4
6
A
V
IN
rising
2.0
2.25
2.5
V
UVLO
THRESHOLD
Under Voltage Lock Out
threshold
V
IN
falling
1.9
2.15
2.4
V
V
IL
(max.)
0.5
V
EN
ENABLE Input Voltage
V
IH
(min.)
1.5
V
I
EN
ENABLE Input Current
V
EN
= 0V to 5.0V
1
5
A
T
J
increasing
145
OT
THRESHOLD
Over-temperature Threshold
T
J
decreasing
135
C
Micrel
MIC2004/MIC2014
August 2005
5
M9999-080305
(408) 955-1690
AC Characteristics
Symbol Parameter
Condition
Min
Typ
Max
Units
t
RISE
Output turn-ON rise time
R
L
= 10
, C
LOAD
= 1
F,
V
OUT
= 10% to 90%
500 1000 1500
s
t
D_LIMIT
Delay before current limiting
MIC2014
77
128
192
ms
t
RESET
Delay before resetting
Kickstart current limit delay,
t
D_LIMIT
Out of current limit following a
current limit event.
MIC2014
77
128
192
ms
t
ON_DLY
Output Turn-on Delay
R
L
= 43
, C
L
= 120F,
C
SLEW
10pF,
V
EN
= 50% to V
OUT
= 10%
1000
1500
s
t
OFF_DLY
Output Turn-off Delay
R
L
= 43
, C
L
= 120F,
C
SLEW
10pF,
V
EN
= 50% to V
OUT
= 90%
700
s
ESD
Symbol Parameter
Condition
Min
Typ
Max
Units
V
OUT
and GND
4
kV
V
ESD_HB
Electro Static Discharge
Voltage: Human Body Model
All other pins
2
kV
V
ESD_MCHN
Electro Static Discharge
Voltage; Machine Model
All pins
Machine Model
200
V
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, 1.5k in series with 100pF.
4. Specification for packaged product only.
5. Requires proper thermal mounting to achieve this performance.
Micrel
MIC2004/MIC2014
August 2005
6
M9999-080305
(408) 955-1690
Timing Diagrams
ENABLE
VOUT
50%
90%
10%
t
ON_DLY
t
OFF_DLY
50%
Switching Delay Times
90%
10%
90%
10%
t
FALL
t
RISE
Rise and Fall Times
90%
10%
t
RISE
VOUT
Output Rise Time
Micrel
MIC2004/MIC2014
August 2005
7
M9999-080305
(408) 955-1690
Typical Characteristics
0
20
40
60
80
100
2
3
4
5
6
SUP
P
LY CUR
RENT
(
A)
V
IN
(V)
Supply Current
Output Enabled
-40C
85C
25C
0
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
2
3
4
5
6
7
SUP
P
L
Y
CURRE
N
T
(
A)
V
IN
(V)
Supply Current
Output Disabled
-40C
85C
25C
0
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
-50 -30 -10 10 30 50 70 90
(
A)
TEMPERATURE (C)
Switch Leakage Current - OFF
1.25
1.30
1.35
1.40
1.45
1.50
1.55
1.60
1.65
-50 -30 -10 10 30 50 70 90
I
LI
M
I
T
(A
)
TEMPERATURE (C)
I
LIMIT
vs. Temperature
(MIC20xx-1.2)
V
IN
= 2.5V
V
IN
= 5V
V
IN
= 3V
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
-50 -30 -10 10 30 50 70 90
I
LI
M
I
T
(A)
TEMPERATURE (C)
5V
3V
2.5V
I
LIMIT
vs. Temperature
(MIC20xx - 0.8)
Please note that
the 3 plots
overlay each
other.
0.55
0.57
0.59
0.61
0.63
0.65
0.67
0.69
0.71
0.73
0.75
-50 -30 -10 10 30 50 70 90
I
LI
MI
T
(A
)
TEMPERATURE (C)
5V
3V
2.5V
I
LIMIT
vs. Temperature
(MIC20xx - 0.5)
0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
-50 -30 -10 10 30 50 70 90
I
LI
MI
T
(A)
TEMPERATURE (C)
I
LIMIT
vs.
Temperature
1.2A
0.8A
0.5A
0
20
40
60
80
100
2
2.5
3
3.5
4
4.5
5
5.5
R
ON
(mOhm)
V
IN
(V)
R
ON
vs.
Supply Voltage
0
20
40
60
80
100
120
-50 -30 -10 10 30 50 70 90
R
ON
(mOhm)
TEMPERATURE (C)
R
ON
vs.
Temperature
2.5V
3.3V
5V
2.05
2.1
2.15
2.2
2.25
2.3
-50
0
50
100
150
TH
RESH
O
L
D (
V
)
TEMPERATURE (C)
UVLO Threshold
vs. Temperature
V RISING
V FALLING
Micrel
MIC2004/MIC2014
August 2005
8
M9999-080305
(408) 955-1690
Functional Characteristics
ENABLE
(2.5V/div)
V
OUT
(1V/div)
I
OUT
(250mA/div)
0
Time (ms)
50
100
150
200
250
300
350
400
450
500
550
V
IN
= 5.0V
R
LOAD
C
LOAD
= 47F
Current Limit Response Thermal Shutdown
ENABLE
(2.5V/div)
V
OUT
(1V/div)
I
OUT
(0.5A/div)
0
Time (ms)
50
100
150
200
250
300
350
400
450 500
550
Kickstart Response
Normal Load with Temporary High Load
ENABLE
(1V/div)
V
OUT
(1V/div)
I
OUT
(0.5A/div)
0
Time (ms)
50
100
150
200
250
300
350 400 450 500
550
Kickstart Response
No Load to Short Circuit
ENABLE
(2.5V/div)
V
OUT
(1V/div)
I
OUT
(0.5A/div)
0
Time (ms)
50
100
150
200
250
300
350
400
450 500
550
Kickstart Response
Normal Load with Temporary Short Circuit
ENABLE
(2.5V/div)
V
OUT
(1V/div)
I
OUT
(0.5A/div)
0
Time (ms)
50
100
150
200
250
300
350
400 450 500
550
Kickstart Response
Device Enabled into a Short Circuit
ENABLE
(2.5V/div)
V
OUT
(1V/div)
I
OUT
(200mA/div)
0
Time (ms)
R
L
C
SLEW
= 0pF
4
8
12
16
20
24
28
32
36
40
Inrush Current Response
MIC20xx-0.5
0F
10F
22F47F 100F
220F
470F
Micrel
MIC2004/MIC2014
August 2005
9
M9999-080305
(408) 955-1690
ENABLE
(2.5V/div)
V
OUT
(1V/div)
V
IN
(1/div)
0
Time (s)
4
8
12
16
20
24
28
32
36
40
44
48
UVLO Increasing
Enable tied to V
IN
ENABLE
(2.5V/div)
V
OUT
(1V/div)
V
IN
(1/div)
0
Enable tied to V
IN
4
8
12
16
20
24
28
32
36
40
44
48
UVLO Decreasing
ENABLE
(2.5V/div)
V
OUT
(1V/div)
I
OUT
(200mA/div)
0
Time (ms)
2
4
6
8
10
12
14
V
IN
= 5.0V
R
LOAD
C
LOAD
= 100F
Turn-On/Turn-Off
Micrel
MIC2004/MIC2014
August 2005
10
M9999-080305
(408) 955-1690
Functional Diagram
V
F
E
R
r
e
w
o
P
T
E
F
r
e
d
n
U
e
g
a
tl
o
V
r
o
t
c
e
t
e
D
l
a
m
r
e
h
T
r
o
s
n
e
S
e
t
a
R
w
e
l
S
l
o
r
t
n
o
C
t
n
e
r
r
u
C
T
E
F
r
o
r
ri
M
y
r
o
t
c
a
F
d
e
t
s
u
j
d
a
ti
m
i
L
t
n
e
r
r
u
C
p
o
o
L
l
o
r
t
n
o
c
l
o
r
t
n
o
C
e
t
a
G
c
i
g
o
L
l
o
r
t
n
o
C
r
e
m
i
T
y
a
l
e
D
d
n
a
ENABLE
GND
VOUT
VIN
Figure 2 MIC2004/2014 Block Diagram
Micrel
MIC2004/MIC2014
August 2005
11
M9999-080305
(408) 955-1690
Functional Description
Input and Output
V
IN
is both the power supply connection for the internal
circuitry driving the switch and the input (Source
connection) of the power MOSFET switch. V
OUT
is the
Drain connection of the power MOSFET and supplies
power to the load. In a typical circuit, current flows from
V
IN
to V
OUT
toward the load. Since the switch is bi-
directional when enabled, if V
OUT
is greater than V
IN
,
current will flow from V
OUT
to V
IN
.
When the switch is disabled, current will not flow to the
load, except for a small unavoidable leakage current of
a few microamps. However, should V
OUT
exceed V
IN
by
more than a diode drop (~0.6V), while the switch is
disabled, current will flow from output to input via the
power MOSFET's body diode. While this effect can be
used to advantage when large bypass capacitors are
placed on MIC2004/2014's's output, it can not be relied
upon to fully or reliably discharge the load capacitance,
because discharging depends upon the characteristics
of the circuitry at VIN.
To ensure proper discharge of any output capacitance,
MIC2004/2014 is equipped with a discharge FET which
is ON any time the device is not Enabled.
Current Sensing and Limiting
MIC2004/2014 protects the system power supply and
load from damage by continuously monitoring current
through the on-chip power MOSFET. Load current is
monitored by means of a current mirror in parallel with
the power MOSFET switch. Current limiting is invoked
when the load exceeds an internally set over-current
threshold. When current limiting is activated the output
current is constrained to the limit value, and remains at
this level until either the load/fault is removed, the load's
current requirement drops below the limiting value, or
the MIC2004/2014 goes into thermal shutdown.
Kickstart (MIC2014 only)
The MIC2014 is designed to allow momentary current
surges (Kickstart) before the onset of current limiting,
which permits dynamic loads, such as small disk drives
or portable printers to draw the energy needed to
overcome inertial loads without sacrificing system
safety. In this respect, the MIC2014 differs markedly
from MIC2004 and its peers, which immediately limit
load current, potentially starving the motor and causing
the appliance to stall or stutter.
During this delay period, typically 128 ms, a secondary
current limit is in effect. If the load demands a current in
excess the secondary limit, MIC2014 acts immediately
to restrict output current to the secondary limit for the
duration of the Kickstart period. After this time the
MIC2014 reverts to its normal current limit. An example
of Kickstart operation is shown below.
T
U
O
T
U
O
Figure 3. Kickstart Operation
Picture Key:
A) MIC2014 is enabled into an excessive load (slew
rate limiting not visible at this time scale) The initial
current surge is limited by either the overall circuit
resistance and power supply compliance, or the
secondary current limit, whichever is less.
B) R
ON
of the power FET increases due to internal
heating (effect exaggerated for emphasis).
C) Kickstart period.
D) Current limiting initiated. FAULT/ goes LOW (Note:
FAULT/ output is not available on MIC2014).
E) V
OUT
is non-zero (load is heavy, but not a dead short
where V
OUT
= 0. Limiting response will be the same
for dead shorts).
F) Thermal shutdown followed by thermal cycling.
G) Excessive load released, normal load remains.
MIC2014 drops out of current limiting.
H) FAULT/ delay period followed by FAULT/ going
HIGH. (FAULT/ output is not available on MIC2014).
Under Voltage Lock Out
Under voltage lock-out insures no anomalous operation
occurs before the device's minimum input voltage of
2.5V had been achieved. Prior to reaching this voltage,
the output switch (power MOSFET) is OFF and no
circuit functions, such as FAULT/ or ENABLE, are
considered to be valid or operative.
Enable
ENABLE is a HIGH true control signal, which activates
Micrel
MIC2004/MIC2014
August 2005
12
M9999-080305
(408) 955-1690
the main MOSFET switch. ENABLE will operate with
logic running from supply voltages as low as 1.8V.
ENABLE can be wire-OR'd with other MIC2004/2014s
or similar devices without damage to the device.
ENABLE may be driven higher than V
IN
, but no higher
than 5.5V.
Slew Rate Control
Large capacitive loads can create significant current
surges when charged through a high-side switch such
as the MIC2004/2014. For this reason, MIC2004/2014
provides built-in slew rate control to limit the initial inrush
currents upon enabling the power MOSFET switch.
Slew rate control is active upon powering up, and upon
re-enabling the load. At shutdown, the discharge slew
rate is controlled by the external load and output
capacitor.
Thermal Shutdown
Thermal shutdown is employed to protect
MIC2004/2014 from damage should the die temperature
exceed safe operating levels. Thermal shutdown shuts
off the output MOSFET if the die temperature reaches
145C.
MIC2004/2014 will automatically resume operation
when the die temperature cools down to 135C. If
resumed operation results in reheating of the die,
another shutdown cycle will occur and the
MIC2004/2014 will continue cycling between ON and
OFF states until the offending load has been removed.
Depending on PCB layout, package type, ambient
temperature, etc., hundreds of milliseconds may elapse
from the incidence of a fault to the output MOSFET
being shut off. This delay is due to thermal time
constants within the system itself. In no event will the
device be damaged due to thermal overload because
die temperature is monitored continuously by on-chip
circuitry.
Micrel
MIC2004/MIC2014
August 2005
13
M9999-080305
(408) 955-1690
Application Information
I
LIMIT
vs. I
OUT
measured
MIC2004/2014's's current limiting circuitry is designed to
act as a constant current source to the load. As the load
tries to pull more than the allotted current, V
OUT
drops
and the input to output voltage differential increases.
When V
IN
-V
OUT
exceeds 1V, I
OUT
drops below I
LIMIT
to
reduce the drain of fault current on the system's power
supply and to limit internal heating of MIC2004/2014.
When measuring I
OUT
it is important to bear this voltage
dependence in mind, otherwise the measurement data
may appear to indicate a problem when none really
exists. This voltage dependence is illustrated in Figures
4 and 5.
In Figure
4 output current is measured as V
OUT
is pulled
below V
IN
, with the test terminating when V
OUT
is 1V
below V
IN
. Observe that once I
LIMIT
is reached I
OUT
remains constant throughout the remainder of the test.
In Figure
5
this test is repeated but with V
IN
- V
OUT
exceeding 1V.
When V
IN
- V
OUT
> 1V, MIC2004/2014's current limiting
circuitry responds by decreasing I
OUT
, as can be seen in
Figure 5. In this demonstration, V
OUT
is being controlled
and I
OUT
is the measured quantity. In real life
applications V
OUT
is determined in accordance with
Ohm's law by the load and the limiting current.
Figure 4. I
OUT
in Current Limiting for V
IN
- V
OUT
1V
Figure 5. I
OUT
in Current Limiting for V
IN
- V
OUT
>1V
This folding back of I
LIMIT
can be generalized by plotting
I
LIMIT
as a function of V
OUT
, as shown below. The slope
of V
OUT
between I
OUT
= 0 and I
OUT
= I
LIMIT
(where I
LIMIT
=
1) is determined by R
ON
of MIC2004/2014 and I
LIMIT
.
0
0.2
0.4
0.6
0.8
1.0
1.2
0
1
2
3
4
5
6
N
O
RM
A
L
IZED
OUTPUT CURRENT (A)
OUTPUT VOLTAGE (V)
Normalized Output Current
vs. Output Voltage (5V)
Figure 6.
Micrel
MIC2004/MIC2014
August 2005
14
M9999-080305
(408) 955-1690
0
0.2
0.4
0.6
0.8
1.0
1.2
0
0.5
1.0
1.5
2.0
2.5
3.0
N
O
RMALIZED OUTPU
T
CURR
ENT (A)
OUTPUT VOLTAGE (V)
Normalized Output Current
vs. Output Voltage (2.5V)
Figure 7.
Kickstart (MIC2014)
Kickstart allows brief current surges to pass to the load
before the onset of normal current limiting, which
permits dynamic loads to draw bursts of energy without
sacrificing system safety.
Functionally, Kickstart is a forced override of the normal
current limiting function provided by MIC2014. The
Kickstart period is governed by an internal timer which
allows current to pass unimpeded to the load for 128ms
and then normal (primary) current limiting goes into
action.
During Kickstart a secondary current limiting circuit is
monitoring output current to prevent damage to the
MIC2014, as a hard short combined with a robust power
supply can result in currents of many tens of amperes.
This secondary current limit is nominally set at 4 Amps
and reacts immediately and independently of the
Kickstart period. Once the Kickstart timer has finished its
count the primary current limiting circuit takes over and
holds I
OUT
to its programmed limit for as long as the
excessive load persists.
Once MIC2014 drops out of current limiting the Kickstart
timer initiates a lock-out period of 128ms such that no
further bursts of current above the primary current limit,
will be allowed until the lock-out period has expired.
Kickstart may be over-ridden by the thermal protection
circuit and if sufficient internal heating occurs, Kickstart
will be terminated and I
OUT
0. Upon cooling, if the
load is still present I
OUT
I
LIMIT
, not I
KICKSTART
.
FAULT/
ENABLE
V
OUT
I
OUT
0
Time (ms)
100
200
300
400
500
600
Kickstart
Current Limiting
Load Removed
Figure 9. Kickstart
Supply Filtering
A 0.1F to 1F bypass capacitor positioned close to the
V
IN
and GND pins of MIC2004/2014 is both good design
practice and required for proper operation of
MIC2004/2014. This will control supply transients and
ringing. Without a bypass capacitor, large current surges
or an output short may cause sufficient ringing on V
IN
(from supply lead inductance) to cause erratic operation
of MIC2004/2014's control circuitry. Good quality, low
ESR capacitors, such as Panasonic's TE or ECJ series,
are suggested.
When bypassing with capacitors of 10F and up, it is
good practice to place a smaller value capacitor in
parallel with the larger to handle the high frequency
components of any line transients. Values in the range
of 0.01F to 0.1F are recommended. Again, good
quality, low ESR capacitors should be chosen.
Power Dissipation
Power dissipation depends on several factors such as
the load, PCB layout, ambient temperature, and supply
voltage. Calculation of power dissipation can be
accomplished by the following equation:
(
)
2
OUT
DS(ON)
D
I
R
P
=
To relate this to junction temperature, the following
equation can be used:
A
A)
-
(J
D
J
T
R
P
T
+
=
Where: T
J
= junction temperature,
Micrel
MIC2004/MIC2014
August 2005
15
M9999-080305
(408) 955-1690
T
A
= ambient temperature
R
(J-A)
is the thermal resistance of the package
In normal operation MIC2004/2014's Ron is low enough
that no significant I
2
R heating occurs. Device heating is
most often caused by a short circuit, or very heavy load,
when a significant portion of the input supply voltage
appears across MIC2004/2014's power MOSFET.
Under these conditions the heat generated will exceed
the package and PCB's ability to cool the device and
thermal limiting will be invoked.
In Figure 10 die temperature is plotted against I
OUT
assuming a constant case temperature of 85C. The
plots also assume a worst case R
ON
of 140 m at a die
temperature of 135C. Under these conditions it is clear
that an SOT-23 packaged device will be on the verge of
thermal shutdown, typically 145C die temperature,
when operating at a load current of 1.25A. For this
reason we recommend using MLF packaged
MIC2004/2014s for any design intending to supply
continuous currents of 1A or more.
Die Temperature vs. Iout for Tcase = 85C
0
20
40
60
80
100
120
140
160
0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00
Iout - Amps
D
i
e T
e
m
p
er
atu
r
e
-
C
SOT-23
MLF
Figure 10. Die Temperature vs. I
OUT
Figure 10 assumes no backside contact is made to the
thermal pad provided on the MLF package. For optimal
performance at higher current levels, or in higher
temperature environments, thermal contact with the
PCB and the exposed power paddle on the back side of
the MLF package should be made. This significantly
reduces the package's thermal resistance and thus
extends the MIC2004/2014's operating range. It should
be noted that this backside paddle is electrically active
and is connected to MIC2004/2014's GND pin.
2 Vias
0.3 mm diam.
to Ground Plane
0.8 mm
1.4 mm
Figure 11. Pad for thermal mounting to PCB
Micrel
MIC2004/MIC2014
9-080305
5-1690
Package Information
5-Pin SOT-23 (M5)
6 Pin 2mmX2mm MLF (ML)
16
M999
(408) 95
August 2005
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.
2004 Micrel, Incorporated.
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