MIC2007/2017
Adjustable 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
The MIC2007 and MIC2017 are current limiting, high-
side power switches, designed for general purpose
power distribution and control in PCs, PDAs, printers
and other self-powered systems.
The MIC2007 and MIC2017's primary functions are
current limiting and power switching. They are thermally
protected and will shutdown should their internal
temperature reach unsafe levels. This protects both the
device and the load under high current or fault
conditions.
Features include: user adjustable output slew rate
limiting, automatic load discharge and under voltage
detection. Both devices offer user programmable current
limiting thereby providing designers a continuous
spectrum of current limits from 200mA to 2 Amps.
The MIC2017 offers a unique new feature: Kickstart
TM
,
which allows momentary high current surges to pass
unrestricted without sacrificing overall system safety.
The MIC2007 and MIC2017 are excellent choices for
USB and IEEE 1394 (FireWire) applications or for any
system where current limiting and power control are
desired.
The MIC2007 and MIC2017 are offered in space saving
6-pin SOT-23 and 2mm x 2mm MLF
TM
packages.
Features
70m typical on-resistance
2.5V 5.5V operating range
User adjustable current limit: 0.2A 2.0A
Kickstart
TM
User adjustable output slew rate control
Automatic load discharge
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
C
SLEW
VOUT
GND
ENABLE
MIC2007
MIC2017
USB
Controller
I
LIMIT
V
BUS
USB
Port
USB
Port
Figure 1. Typical Application Circuit
October 2005
M9999-102805
Micrel
MIC2007/MIC2017
October 2005
2
M9999-102805
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
MIC2007YM6 FHAA
SOT-23-6
MIC2007YML
(2)
HAA
No
2mm X 2mm MLF
MIC2017YM6 FQAA
SOT-23-6
MIC2017YML
(2)
QAA
0.2A 2.0A
Yes
Yes
2mm X 2mm MLF
Notes:
1. Under-bar symbol ( _ ) may not be to scale.
2. Consult Factory for availability
Micrel
MIC2007/MIC2017
October 2005
3
M9999-102805
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
C
SLEW
I
LIMIT
V
IN
GND
ENABLE
6-Pin 2mm X 2mm MLF (ML)
Top View
ENABLE
GND
V
OUT
I
LIMIT
VIN
3
1
6
2
4
5 C
SLEW
SOT 23-6 (M6)
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
MIC2007/2017'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
I
LIMIT
Input Sets the current limit threshold via a resistor connected between I
LIMIT
and
GND.
I
LIMIT
= Current Limiting Factor (CLF) / R
SET
.
5 2
CSLEW
Input
Slew rate control. Adding a small value capacitor between this pin and VIN
slows turn-ON of the power FET.
6 1
VOUT
Output
Switch output. The load being driven by MIC2007/2017 is connected to this
pin.
Micrel
MIC2007/MIC2017
October 2005
4
M9999-102805
Absolute Maximum Ratings
(1)
All pins ...........................................................0.3 to 6V
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-23-6
....................................................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
1.2
10
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
OUT
= 2.0A, V
OUT
= 0.8V
IN
210
250
286
V
I
OUT
= 1.0A, V
OUT
= 0.8V
IN
190
243
293
V
I
OUT
= 0.5A, V
OUT
= 0.8V
IN
168
235
298
V
CLF
Current Limit: Factor
R
SET
() = CLF (V)
I
OUT
(A)
I
OUT
= 0.2A, V
OUT
= 0.8V
IN
144
225
299
V
I
LIMIT_2nd
Secondary current limit
(Kickstart)
MIC2017, 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
MIC2007/MIC2017
October 2005
5
M9999-102805
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
MIC2017
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.
MIC2017
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
Electrostatic Discharge
Voltage: Human Body Model
All other pins
2
kV
V
ESD_MCHN
Electrostatic 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
MIC2007/MIC2017
October 2005
6
M9999-102805
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
MIC2007/MIC2017
October 2005
7
M9999-102805
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
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
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
215
220
225
230
235
240
245
250
0
0.5
1.0
1.5
2.0
CURRENT LI
MI
T FACTOR
CURRENT LIMIT (A)
Current Limit Factor
vs. Temperature @ 2.5V
85C
25
C
-40
C
215
220
225
230
235
240
245
250
0
0.5
1.0
1.5
2.0
C
URR
EN
T LI
MI
T FAC
T
O
R
CURRENT LIMIT (A)
Current Limit Factor
vs. Temperature @ 3V
25C
85C
-40C
215
220
225
230
235
240
245
250
0
0.5
1.0
1.5
2.0
C
URR
EN
T LI
MI
T FA
CTO
R
CURRENT LIMIT (A)
Current Limit Factor
vs. Temperature @ 5V
85C
25
C
-40
C
215
220
225
230
235
240
245
250
0
0.5
1.0
1.5
2.0
C
URR
EN
T LI
MI
T FAC
T
O
R
CURRENT LIMIT (A)
Current Limit Factor
vs. Input Voltage @ -40C
5V
2.5V
3V
Note:
The 2.5V and 3V
plots overlap.
215
220
225
230
235
240
245
250
0
0.5
1.0
1.5
2.0
C
URR
EN
T LI
MI
T FAC
T
O
R
CURRENT LIMIT (A)
Current Limit Factor
vs. Input Voltage @ 25C
5V
3V
2.5V
215
220
225
230
235
240
245
250
0
0.5
1.0
1.5
2.0
C
URR
EN
T LI
MI
T FAC
T
O
R
CURRENT LIMIT (A)
Current Limit Factor
vs. Input Voltage @ 85C
5V
3V
2.5V
Micrel
MIC2007/MIC2017
October 2005
8
M9999-102805
Functional Characteristics
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
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
Inrush Current
R
Inrush Current Res
0F
10F
22F47F 100F
220F
470F
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
(150mA/div)
0
Time (s)
2000
6000
10000
14000
18000
22000
V
IN
= 5.0V
R
LOAD
C
LOAD
= 0F
0pF 100pF
820pF
1800pF
2700pF 3500pF
C
SLEW
Response
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
ponse
Inrush Current Response
Inrush Current Response
Micrel
MIC2007/MIC2017
October 2005
9
M9999-102805
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
Micrel
MIC2007/MIC2017
October 2005
10
M9999-102805
Functional Diagram
ENABLE
VIN
VOUT
GND
V
REF
Power
FET
Slew Rate
Control
Current
Mirror FET
Current Limit
Control Loop
Gate Control
Under
Voltag e
Detector
Thermal
Sensor
Control Logic
and Delay Timer
I
LIMIT
C
SLEW
Figure 2. MIC2007/2017 Block Diagram
Micrel
MIC2007/MIC2017
October 2005
11
M9999-102805
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 MIC2007/2017'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,
MIC2007/2017 is equipped with a discharge FET which
is ON any time the device is not Enabled.
Current Sensing and Limiting
The MIC2007/2017 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 externally 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 MIC2007/2017 goes into
thermal shutdown.
Kickstart (MIC2017 only)
The MIC2017 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 MIC2017 differs markedly
from MIC2007 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 of the secondary limit, the MIC2017 acts
immediately to restrict output current to the secondary
limit for the duration of the Kickstart period. After this
time, the MIC2017 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) MIC2017 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:
MIC2007/2017 does not provide a FAULT/ output.)
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.
MIC2017 drops out of current limiting.
H) FAULT/ delay period followed by FAULT/ going
HIGH. (Note: MIC2007/2017 does not provide a
FAULT/ output.)
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 ENABLE, are considered to be
valid or operative.
Micrel
MIC2007/MIC2017
October 2005
12
M9999-102805
Enable
ENABLE is a HIGH true control signal, which activates
the main MOSFET switch. ENABLE will operate with
logic running from supply voltages as low as 1.8V, once
V
IN
has exceeded the UVLO threshold. ENABLE can be
wire-OR'd with other MIC2007/2017s 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 MIC2007/2017. For this reason, the
MIC2007/2017 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.
On MIC2007/2017 slew rate is adjustable and can be
further reduced by adding an external capacitance
between VIN and the CSLEW pins.
Thermal Shutdown
Thermal shutdown is employed to protect the
MIC2007/2017 from damage should the die temperature
exceed safe operating levels. Thermal shutdown shuts
off the output MOSFET if the die temperature reaches
145C.
The MIC2007/2017 will automatically resume operation
when the die temperature cools down to 135C. If
resumed operation results in reheating of the die, then
another shutdown cycle will occur and the
MIC2007/2017 will continue cycling between ON and
OFF states until the offending load has been removed.
Depending upon 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
MIC2007/MIC2017
October 2005
13
M9999-102805
Application Information
Setting I
LIMIT
The MIC2007/2017's current limit is user programmable
and controlled by a resistor connected between the I
LIMIT
pin and Ground. The value of this resistor is determined
by the following equation:
I
LIMIT
= Current Limit Factor (CLF)
R
SET
or
R
SET
() = Current Limit Factor (V)
I
LIMIT
(A)
Example:
Set I
LIMIT
= 1.25A
Looking in the Electrical specifications we will find CLF
at I
LIMIT
= 1A. For the sake of this example, we will say
the typical value of CLF at an I
OUT
of 1A is 235V.
Applying the equation above:
R
SET
() = 235 V
1.25 A
R
SET
= 188
Designers should be aware that variations in the
measured I
LIMIT
for a given R
SET
resistor, will occur
because of small differences between individual ICs
(inherent in silicon processing) resulting in a spread of
I
LIMIT
values. In the example above we used the typical
value of CLF to calculate R
SET
. We can determine I
LIMIT
's
spread by using the minimum and maximum values of
CLF and the calculated value of R
SET
.
R
SET
= 187
(the closest standard 1% value)
I
LIMIT_MIN
= 210V = 1.12A
187
I
LIMIT_MIN
= 260V = 1.39A
187
Giving us a maximum I
LIMIT
variation over temperature
of:
I
LIMIT_MIN
I
LIMIT_TYP
I
LIMIT_MAX
1.12A 1.25A 1.39A
or
1.25A
11%
I
LIMIT
vs. I
OUT
measured
The MIC2007/2017'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 the
MIC2007/2017.
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, the MIC2007/2017'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.
Micrel
MIC2007/MIC2017
October 2005
14
M9999-102805
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 MIC2007/2017 and I
LIMIT
.
0
0.2
0.4
0.6
0.8
1.0
1.2
0
1
2
3
4
5
6
NORMALIZED
OUTPU
T
C
URREN
T
(A)
OUTPUT VOLTAGE (V)
Normalized Output Current
vs. Output Voltage (5V)
Figure 6.
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
NORMALIZED OU
TPUT CUR
RENT (A)
OUTPUT VOLTAGE (V)
Normalized Output Current
vs. Output Voltage (2.5V)
Figure 7.
C
SLEW
The CSLEW input is provided to increase control of the
output voltage ramp at turn-on. This input allows
designers the option of decreasing the output's slew rate
(slowing the voltage rise) by adding an external
capacitance between the pin, CSLEW, and VIN. This
capacitance slows the rate at which the pass FET gate
voltage increases and thus, slows both the response to
an Enable command as well as V
OUT
's ascent to its final
value.
Figure 8 illustrates effect of C
SLEW
on turn-ON delay and
output rise time.
Micrel
MIC2007/MIC2017
October 2005
15
M9999-102805
0
0.002
0.004
0.006
0.008
0.01
0.012
0.014
0 0 0 0 0 0 0 0 0 0
TIME
(mS)
C
SLEW
(nF)
Typical Turn-on Times
vs. External C
SLEW
Capacitance
2
4
6
8
10
12
14
0
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5
T
RISE
T
DELAY
T
ON
Figure 8.
C
SLEW
's effect on I
LIMIT
An unavoidable consequence of adding C
SLEW
capacitance is a reduction in the MIC2008/2018's ability
to quickly limit current transients or surges. A
sufficiently large capacitance can prevent both the
primary and secondary current limits from acting in time
to prevent damage to the MIC2008/2018 or the system
from a short circuit fault. For this reason, the upper limit
on the value of C
SLEW
is 4nF.
Kickstart (MIC2017)
Kickstart allows brief current surges to pass to the load
before the onset of normal current limiting. This, in turn,
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 the MIC2017. 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
MIC2017. This is because 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 the MIC2017 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 Operation with Varying Load
Supply Filtering
A 0.1F to 1F bypass capacitor positioned close to the
V
IN
and GND pins of MIC2007/2017 is both good design
practice and required for proper operation of the
MIC2007/2017. 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 the MIC2007/2017'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
Micrel
MIC2007/MIC2017
October 2005
16
M9999-102805
equation can be used:
A
A)
-
(J
D
J
T
R
P
T
+
=
Where: T
J
= junction temperature,
T
A
= ambient temperature
R
(J-A)
is the thermal resistance of the package
In normal operation, the MIC2007/2017's R
on
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 the MIC2007/2017'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, it is recommend that MLF package be used for
any MIC2007/2017 designs 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
at
u
r
e
-
C
SOT-23
MLF
Figure 10. Die Temperature vs. Package
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 thereby
extending the MIC2007/2017's operating range. It
should be noted that this backside paddle is electrically
active and is connected to the MIC2007/2017'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
MIC2007/MIC2017
Package Information
6-Pin SOT-23 (M6)
6-Pin 2mm X 2mm MLF (ML)
October 2005
17
M9999-102805
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.
2005 Micrel, Incorporated.
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