Replacement of
CS5208-XX
MIK5208-XX
8 A Low Dropout Positive
Voltage Regulator
September 2000 - revised February 2001
Description
The MIK5208 series of positive adjustable and fixed regulators are designed to provide 8A with higher efficiency than currently available
devices. All internal circuitry is designed to operate down to 700 mV input to output differential and the dropout voltage is fully specified
as a function of load current. Dropout voltage of the device is 100 mV at light loads and rising to 700 mV at maximum output current. A
second low current input is required to achieve this dropout. The MIK5208 can also be used as a single supply device (3 pin version).
On-chip trimming adjusts the reference voltage to 1%.
The MIK5208 series are ideal to power the next generation of advanced microprocessor on motherboards where both 5V and 3.3V
supplies are available.
Features
Adjustable or Fixed Output
Output Current of 8A
Low Dropout, 700 mV at 8A Output Current
0.04% Line Regulation
0.1% Load Regulation
100% Thermal Limit Burn-In
Fast Transient Response
Remote Sense
Applications
High Efficiency Linear Regulators
Post Regulators for Switching Supplies
Microprocessor Supply
Adjustable Power Supply
Typical application data 2.5V, 8A
regulator
V
POWER
V
CONTROL
V
OUT
V
SENSE
Load
MIK5208
10 F
10V
5V
3.3V
100 F
5V
0.1 F
5V
300 F
5V
2.5V@8A
124
1%
124
1%
V
OUT
=
I
R2
ADJ
V
(1+R2/R1) +
REF
Adjust
R2
R1
Package information
Absolute Maximum Ratings
Symbol Parameter
Maximum
Units
P
D
Power Dissipation
Internally Limited
W
V
IN
Input Voltage
Vpower
Vcontrol
7
13
V
T
J
Operating Junction Temperature Range
o
C
Control Section
Power Transistor
0 to 125
0 to150
T
STG
Storage Temperature
-65 to 150
o
C
T
LEAD
Lead Temperature (Soldering, 10 sec)
300
o
C
Device Selection Guide
(Note1)
Device Output
Voltage
MIK5208 Adj
MIK5208-1.5 1.5V
MIK5208-2.5 2.5V
MIK5208-2.85 2.85V
MIK5208-3.0 3.0V
MIK5208-3.3 3.3V
MIK5208-3.5 3.5V
MIK5208-5.0 5.0V
Note 1: Other fixed versions are available Vout = 1.5V to 5.0V
Page 1 of 6
Replacement of
CS5208-XX
MIK5208-XX
8 A Low Dropout Positive
Voltage Regulator
September 2000 - revised February 2001
Electrical Characteristics
(Note 1)
Electrical Characteristics at I
LOAD
= 0 mA and T
J
= +25
C unless otherwise specified.
Parameter Device
Test
Conditions
Min
Typ
Max
Units
V
CONTROL
= 2.75V, V
POWER
= 2V, I
LOAD
= 10mA
1.238 1.250 1.262
Reference Voltage
MIK5208
V
CONTROL
= 2.7V to 12V,
V
POWER
= 3.3V to 5.5V,
I
LOAD
= 10mA to 8A
* 1.230
1.250
1.270
V
V
CONTROL
= V
OUT
+ 1.5V, V
POWER
= V
OUT
+ 0.5V,
Variation from nominal V
OUT
-1 +1
%
Output Voltage
All fixed
versions
V
CONTROL
= V
OUT
+ 1.5V, V
POWER
= V
OUT
+ 0.8V,
I
LOAD
= 0 mA to 8A,
Variation from nominal V
OUT
* -1.6 +1.6
%
Line Regulation
All
I
LOAD
= 10mA, (1.5V+ V
OUT
)
V
CONTROL
12V,
0.8V
(V
POWER
- V
OUT
)
5.5V
* 0.04
0.20
Load Regulation
All
V
CONTROL
= V
OUT
+2.5V, V
POWER
= V
OUT
+ 0.8V,
I
LOAD
= 10mA to 8A
* 0.08
0.40
%
Minimum Load
Current (Note 2)
MIK5208 V
CONTROL
= 5V, V
POWER
= 3.3V, V
ADJ
= 0V
*
1.7
5
mA
Control Pin Current
(Note3)
All V
CONTROL
= V
OUT
+2.5V, V
POWER
= V
OUT
+ 0.8V,
I
LOAD
= 10mA to 8A
*
200
mA
Ground Pin Current All fixed
versions
V
CONTROL
= V
OUT
+2.5V, V
POWER
= V
OUT
+ 0.8V,
I
LOAD
= 10mA to 8A
* 6 10
mA
Adjust Pin Current MIK5208
V
CONTROL
= 2.75V, V
POWER
= 2.05V,
I
LOAD
= 10mA
* 50
120 A
Current Limit
All
(V
IN
- V
OUT
) = 3V
*
8
10
A
Ripple Rejection
All
V
CONTROL
= V
POWER
= V
OUT
+ 2.5V, V
RIPPLE
= 1V
P-P
,
I
LOAD
= 4A
60 80
dB
Thermal Regulation MIK5208
T
A
= 25
C, 30 ms pulse
0.003
%/W
Dropout Voltage Note 4
V
POWER
= V
OUT
+0.8V, I
LOAD
= 10mA
1.00
1.15
Control Input
(V
CONTROL
- V
OUT
)
All
V
POWER
= V
OUT
+ 0.8V, I
LOAD
= 8A
*
1.15
1.30
V
Power Input
(V
POWER
- V
OUT
)
All V
CONTROL
= V
OUT
+ 2.5V, I
LOAD
= 8A
*
0.55
0.70
V
The * denotes the specifications which apply over the full temperature range.
Note 1: Unless otherwise specified Vout = Vsense. For MIK5208 (adj) Vadj = 0V
Note 2: For the adjustable device the minimum load current is the minimum current required to maintain regulation. Normally the current
in the resistor divider used to set the output voltage is selected to meet the minimum load current requirement.
Note 3: The control pin current is the drive current required for the output transistor. This current will track output current with a ratio of
about 1:100.
Note 4: The dropout voltage for the MIK5208 is caused by either minimum control voltage or minimum power voltage.
The specifications represent the minimum input/output voltage required to maintain 1% regulation.
Page 2 of 6
Replacement of
CS5208-XX
MIK5208-XX
8 A Low Dropout Positive
Voltage Regulator
September 2000 - revised February 2001
Pin Functions (5-Lead)
Sense (Pin 1): This pin is the positive side of the reference
voltage. With this pin it is possible to Kelvin sense the output
voltage at the load.
Adjust (Pin 2): This pin is the negative side of the reference
voltage. Adding a small bypass capacitor from the Adjust pin to
ground improves the transient response. For fixed voltage
devices the Adjust pin is also brought out to allow the user to
add a bypass capacitor.
GND (Pin 2): For fixed voltage devices this is the bottom of the
resistor divider that sets the output voltage.
V
POWER
(Pin 5): This pin is the collector of the power transistor.
The output load current is supplied through this pin. The
voltage at this pin must be 0.7V greater than the output voltage
for the device to regulate.
V
CONTROL
(Pin 4): This pin is the supply pin for the control
circuitry. The current flow into this pin will be about 1% of the
output current. The voltage at this pin must be 1.3V greater
than the output voltage for the device to regulate.
Output (Pin 3): This is the power output of the device.
Block Diagram
Page 3 of 6
Replacement of
CS5208-XX
MIK5208-XX
8 A Low Dropout Positive
Voltage Regulator
September 2000 - revised February 2001
Application Information
The MIK5208 series of adjustable and fixed
regulators are designed to power the new generation of
microprocessors. The MIK5208 is designed to make use of
multiple power supplies, present in most systems, to reduce
the dropout voltage. One of the advantages of the two supply
approach is maximizing the efficiency.
The second supply is at least 1V greater than output
voltage and is providing the power for the control circuitry and
supplies the drive current to the NPN output transistor. This
allows the NPN output transistor to be driven into saturation.
For the control voltage the current requirement is small equal
to about 1% of the output current or approximately 80 mA for a
8A load. This drive current becomes part of the output current.
The maximum voltage on the Control pin is 12V. The
maximum voltage at the Power pin is 7V. By tying the control
and power inputs together the MIK5208 can also be operated
as a single supply device. In single supply operation the
dropout will be determined by the minimum control voltage.
The new generation of microprocessors cycle load
current from several hundred milliamperes to several amperes
in tens of nanoseconds. Output voltage tolerances are tighter
and include transient response as part of the specification.
Designed to meet the fast current load step requirements of
these microprocessors, the MIK5208 also saves total cost by
needing less output capacitance to maintain regulation.
Both the fixed and adjustable versions have remote
sense pins, permitting very accurate regulation of output
voltage. As a result, over an output current range of 100mA to
8A, the typical load regulation is less than 1mV. For the fixed
voltages the adjust pin is brought out allowing the user to
improve transient response by bypassing the internal resistor
divider. Optimum transient response is provided using a
capacitor in the range of 0.1
F to 1F for bypassing the Adjust
pin.
In addition to the enhancements mentioned, the
reference accuracy has been improved a factor of two with a
quaranteed initial tolerance of
1% at 25
0
C and 1.6% accuracy
over the full temperature and load current range.
Typical applications for the MIK5208 include 3.3V to
2.5V conversion with a 5V control supply, 5V to 4.2V
conversion with a 12V control supply or 5V to 3.6V conversion
with a 12V control supply. It is easy to obtain dropout voltages
of less than 0.5V at 4A along with excellent static and dynamic
specifications. The device is fully protected against overcurrent
and overtemperature conditions.
Grounding and Output Sensing
The MIK5208 allows true Kelvin sensing for both the
high and low side of the load. As a result the voltage regulation
at the load can be easily optimized. Voltage drops due to
parasitic resistances between the regulator and the load can
be placed inside the regulation loop. The advantages of
remote sensing are illustrated in figures 1 through 3.
Figure 1 shows the device connected as a
conventional 3 terminal regulator with the Sense lead
connected directly to the output of the device. R
P
is the
parasitic resistance of the connections between the device and
the load. Trace A of figure 3 illustrates the effect of Rp.
Figure 2 shows the device connected to take advantage of the
remote sense feature. The Sense pin and the top of the
resistor divider are connected to the top of the load; the bottom
of the resistor divider is connected to the bottom of the load.
The effect on output regulation can be seen in trace B of figure
3.
It is important to note that the voltage drops due to
R
P
are not eliminated; they will add to the dropout voltage of
the regulator regardless. The MIK5208 can control the voltage
at the load as long as the input-output voltage is greater than
the total of the dropout voltage of the device plus the voltage
drop across R
P
.
POWER
SENSE
OUTPUT
ADJ
R
P
R
P
CONTROL
MIK5208
3.3V
5.0V
LOAD
R1
R2
Figure 1. Conventional Load Sensing
POWER
SENSE
OUTPUT
ADJ
R
P
R1
R2
R
P
CONTROL
MIK5208
3.3V
5.0V
LOAD
Figure 2. Remote Load Sensing
V
OUT
V
OUT
FIGURE 1
A
B
FIGURE 2
TIME
I
OUT
(I
)(R )
OUT
P
Figure 3. Remote Sensing Improves Load Regulation
Stability
The circuit design used in the MIK5208 series
requires the use of an output capacitor as part of the device
frequency compensation. The addition of 150
F aluminum
electrolytic or a 22
F solid tantalum on the output will ensure
Page 4 of 6
Replacement of
CS5208-XX
MIK5208-XX
8 A Low Dropout Positive
Voltage Regulator
September 2000 - revised February 2001
stability for all operating conditions. In order to meet the
transient performance of the processor larger value capacitors
are needed. To limit the high frequency noise generated by the
processor high quality bypass capacitors must be used. In
order to limit parasitic inductance (ESL) and resistance (ESR)
in capacitors to acceptable limits, multiple small ceramic
capacitor in addition to high quality solid tantalum capacitors
are required.
When the adjustment terminal is bypassed to
improve the ripple rejection, the requirement for an output
capacitor increases. The Adjust pin is brought out on the fixed
voltage device specifically to allow this capability. To further
improve stability and transient response of these devices
larger values of output capacitor can be used.
The modern processors generate large high
frequency current transients.
Figure 4.
The load current step contains higher order
frequency components than the output coupling network must
handle until the regulator throttles to the load current level.
Because they contain parasitic resistance and inductance,
capacitors are not ideal elements. These parasitic elements
dominate the change in output voltage at the beginning of a
transient load step change. The ESR of the output capacitors
produces an instantaneous step in output voltage
V=I(ESR).
The ESL of the output capacitors produces a droop
proportional to the rate of change of the output current
V=L(
I/t). The output capacitance produces a change in
output voltage proportional to the time until the regulator can
respond
V=t(I/C). Figure 4 illustrates these transient
effects.
Output Voltage
The MIK5208 (adjustable version) develops a 1.25V
reference voltage between the Sense pin and the Adjust pin
(Figure 5). Placing a resistor between these two terminals
causes a constant current to flow though R1 and down though
R2 to set the output voltage. In general R1 is chosen so that
this current is the specified minimum load current of 5 mA. The
current out of the Adjust pin is small, typically 50
A and it adds
to the current from R1. For best regulation the top of the
resistor divider should be connected directly to the Sense pin.
POWER
SENSE
OUTPUT
ADJ
R1
R2
V
OUT
I
ADJ
50 A
V
REF
V
OUT
=
I
R2
ADJ
V
(1+R2/R1) +
REF
V
POWER
V
CONTROL
CONTROL
MIK5208
+
+
+
Figure 5. Setting Output Voltage
Protection Diodes
In normal operation MIK5208 family does not need
any protection diodes between the adjustment pin and the
output and from the output to the input to prevent die
overstress. Internal resistors are limiting the internal current
paths on the ADJ pin. Therefore even with bypass capacitors
on the adjust pin no protection diode is needed to ensure
device safety under short-circuit conditions. The Adjust pin can
be driver on a transient basis
7V with respect to the output
without any device degradation.
A protection diode between the Output pin and
V
POWER
pin is not usually needed. Microsecond surge currents
of 50A to 100A can be handled by the internal diode between
the Output pin and V
POWER
pin of the device. In normal
operations it is difficult to get those values of surge currents
even with the use of large output capacitances. Only with high
value output capacitors, such as 1000
F to 5000F and the
V
POWER
pin is instantaneously shorted to ground, damage can
occur. A diode from output to input is recommended (Figure 6).
POWER
SENSE
OUTPUT
ADJ
D1
D2
R1
R2
V
OUT
V
POWER
V
CONTROL
CONTROL
MIK5208
+
+
+
Figure 6. Optional Clamp Diodes Protect Against Input
Crowbar Circuits
If MIK5208 is connected as a single supply device
with the control and power input pins shorted together the
internal diode between the output and the power input pin will
protect the control input pin.
Thermal Considerations
The MIK5208 series have internal power and
thermal limiting circuitry designed to protect the device under
overload conditions. However maximum junction temperature
ratings should not be exceeded under continuous normal load
conditions. Careful consideration must be given to all sources
of thermal resistance from junction to ambient, including
junction-to-case, case-to-heat sink interface and heat sink
resistance itself.
Junction temperature of the Control section can run
up to 125
0
C. Junction temperature of the Power section can
run up to 150
0
C. Due to the thermal gradients between the
power transistor and the control circuitry there is a significant
difference in thermal resistance between the Control and
Power sections.
Virtually all the power dissipated by the device is
dissipated in the power transistor. The temperature rise in the
power transistor will be greater than the temperature rise in the
Control section making the thermal resistance lower in the
Control section. At power levels below 12W the temperature
gradient will be less than 25
0
C and the maximum ambient
temperature will be determined by the junction temperature of
the Control section. This is due to the lower maximum junction
temperature in the Control section. At power levels above 12W
the temperature gradient will be greater than 25
0
C and the
maximum ambient temperature will be determined by the
Power section. In both cases the junction temperature is
determined by the total power dissipated in the device. For
Page 5 of 6
Replacement of
CS5208-XX
MIK5208-XX
8 A Low Dropout Positive
Voltage Regulator
September 2000 - revised February 2001
most low dropout applications the power dissipation will be
less than 12W.
The power in the device is made up of two
components: the power in the output transistor and the power
in the control circuit.
The power in the control circuit is negligible.
The power in the control circuit is equal to:
P
CONTROL
= (V
CONTROL
- V
OUT
)(I
CONTROL
)
where I
CONTROL
is equal I
OUT
/ 100(typ)
The power in the output transistor is equal to:
P
OUTPUT
= (V
POWER
- V
OUT
)(I
OUT
)
The total power is equal to:
P
TOTAL
= P
CONTROL
+ P
OUTPUT
Junction-to-case thermal resistance is specified from
the IC junction to the bottom of the case directly below the die.
This is the lowest resistance path for the heat flow. In order to
ensure the best possible thermal flow this area of the package
to the heat sink proper mounting is required. Thermal
compound at the case-to-heat sink interface is recommended.
A thermally conductive spacer can be used, if the case of the
device must be electrically isolated, but its added contribution
to thermal resistance has to be considered.
Pad Location
Chip size 3.1 mm x 2.62 mm
Pad Location Coordinates
Pad Center Coordinates
(mm)
Pad
N
Name
X Y
1 V
POWER
(Note 1) (Note 2)
1550
2225
2
Output (Note 2)
430
1800
3
Output (Note 2)
2670
1800
4 V
POWER
(Note 1) (Note 2)
1550
1375
5 V
CONTROL
(Note 1)
1250
935
6
Sense (Note 1)
205
665
7
Adjust (for adjustable output)
GND (for fixed output)
205 205
Other pads are used for trimming.
Note 1: For 3 - lead version 1, 4, 5 pads connect to Vin and 6 pad to Output.
Note 2: Double bond pad.
Page 6 of 6
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