MP8675
6A, 42V, 420kHz Step-Down Converter
with Synchronizable Gate Driver
The Future of Analog IC Technology
DESCRIPTION
The MP8675 is a monolithic step-down switch
mode converter with a built in, internal high-side
power MOSFET. It achieves 6A continuous
output current over a wide input supply range
with excellent load and line regulation.
Current mode operation provides fast transient
response and eases loop stabilization.
Fault condition protection includes cycle-by-cycle
current limiting and thermal shutdown.
The MP8675 requires a minimum number of
readily available standard external components
and is available in an 8-pin SOIC package with
exposed pad.
FEATURES
•
•
•
•
•
•
•
•
•
•
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Wide 4.5V to 42V Operating Input Range
6A Continuous Output Current
100mΩ Internal Power MOSFET Switch
Synchronizable Gate Driver Delivers up to
95% Efficiency
Fixed 420kHz Frequency
Synchronizable up to 1.5MHz
Over Current Latch Off Protection
Thermal Shutdown
Output Adjustable from 0.8V
Stable with Low ESR Output Ceramic
Capacitors
Available in a Thermally Enhanced 8-Pin
SOIC Package
Digital Set Top Boxes
Personal Video Recorders
Broadband Communications
Flat Panel Television and Monitors
APPLICATIONS
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“MPS” and “The Future of Analog IC Technology” are Registered Trademarks of
Monolithic Power Systems, Inc.
TYPICAL APPLICATION
8
2
IN
BST
100
95
Efficiency vs.
Output Current
V
IN
=12V
V
IN
=5V
MP8675
SW
3
VCC
BG
7
1
EFFICIENCY (%)
90
85
80
75
70
65
60
0
V
IN
=42V
V
O
=3.3V
1
2
3
4
5
6
OUTPUT CURRENT (A)
7
4
OFF ON
EN/SYNC
GND
5
FB
6
MP8675 Rev.1.2
1/26/2010
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2010 MPS. All Rights Reserved.
1
MP8675 – 6A, 42V, 420KHZ STEP-DOWN WITH SYNCHRONIZABLE GATE DRIVER
ORDERING INFORMATION
Part Number*
MP8675DN
Package
SOIC8E
Top Marking
MP8675DN
Free Air Temperature (T
A
)
–40°C to +85°C
* For Tape & Reel, add suffix –Z (e.g. MP8675DN–Z).
For RoHS Compliant packaging, add suffix –LF (e.g. MP8675DN–LF–Z)
PACKAGE REFERENCE
1
2
3
4
8
7
6
5
ABSOLUTE MAXIMUM RATINGS
(1)
Thermal Resistance
(4)
Supply Voltage V
IN
....................................... 45V
V
SW
...................... –0.3V (–5V for < 10ns) to 46V
V
BST
– V
SW
...................................................... 6V
All Pins ...........................................–0.3V to +6V
(2)
Continuous Power Dissipation (T
A
= +25°C)
………………………………………………....2.5W
Junction Temperature ...............................150°C
Lead Temperature ....................................260°C
Storage Temperature.............. –65°C to +150°C
SOIC8E ...................................50 ...... 10 ...
°C/W
Notes:
1) Exceeding these ratings may damage the device.
2) 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 continuous power dissipation at
any ambient temperature is calculated by P
D
(MAX) = (T
J
(MAX)-T
A
)/θ
JA
. Exceeding the maximum allowable power
dissipation will cause excessive die temperature, and the
regulator will go into thermal shutdown. Internal thermal
shutdown circuitry protects the device from permanent
damage.
3) The device is not guaranteed to function outside of its
operating conditions.
4) Measured on JESD51-7, 4-layer PCB.
θ
JA
θ
JC
Recommended Operating Conditions
(3)
Supply Voltage V
IN
...........................4.5V to 42V
Operating Junct. Temp (T
J
)..... –40°C to +125°C
MP8675 Rev.1.2
1/26/2010
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2010 MPS. All Rights Reserved.
2
MP8675 – 6A, 42V, 420KHZ STEP-DOWN WITH SYNCHRONIZABLE GATE DRIVER
ELECTRICAL CHARACTERISTICS
V
IN
= 12V, T
A
= +25°C, unless otherwise noted.
Parameters
Feedback Voltage
Feedback Current
Switch On Resistance
(5)
Switch Leakage
Current Limit
5)
Oscillator Frequency
Fold-back Frequency
Maximum Duty Cycle
Minimum On Time
(5)
Under Voltage Lockout Threshold Rising
Under Voltage Lockout Threshold Hysteresis
EN Input Low Voltage
EN Input High Voltage
EN Input Current
Sync Frequency Range (Low)
Sync Frequency Range (High)
Enable Turnoff Delay
Supply Current (Shutdown)
Supply Current (Quiescent)
Thermal Shutdown
BG Driver Bias Supply Voltage
Gate Driver Sink Impedance
(5)
Gate Driver Source Impedance
(5)
Gate Drive Current Sense Trip Threshold
Note:
5) Guaranteed by design.
Symbol Condition
V
FB
4.5V
≤
V
IN
≤
42V
I
FB
V
FB
= 0.8V
R
DS(ON)
V
EN
= 0V, V
SW
= 0V
f
SW
V
FB
= 0.6V
V
FB
= 0V
V
FB
= 0.6V
Min
0.788
7.5
240
25
85
3.90
t
ON
Typ
0.808
10
100
0.1
8.0
420
115
90
100
4.10
880
Max
0.828
10
600
205
4.30
0.4
2
V
EN
= 2V
V
EN
= 0V
F
SYNCL
F
SYNCH
T
OFF
V
EN
= 0V
V
EN
= 2V, V
FB
= 1V
V
CC
R
SINK
R
SOURCE
V
SW
I
CC
= 5mA
4.5
2
0.1
300
1.5
5.0
1
0.9
150
5.0
1
4
20
Units
V
nA
mΩ
µA
A
kHz
kHz
%
ns
V
mV
V
V
µA
kHz
MHz
µs
µA
mA
°C
V
Ω
Ω
mV
10
1.1
MP8675 Rev.1.2
1/26/2010
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2010 MPS. All Rights Reserved.
3
MP8675 – 6A, 42V, 420KHZ STEP-DOWN WITH SYNCHRONIZABLE GATE DRIVER
PIN FUNCTIONS
Pin #
1
2
3
4
5
Name
SW
Description
Switch Output.
Bootstrap. This capacitor is needed to drive the power switch’s gate above the supply
BST
voltage. It is connected between SW and BS pins to form a floating supply across the
power switch driver.
VCC
BG Driver Bias Supply. Decouple with a 1µF ceramic capacitor to GND.
BG
Gate Driver Output. Connect this pin to the gate of the synchronous MOSFET.
Ground. This pin is the voltage reference for the regulated output voltage. For this reason
GND,
care must be taken in its layout. This node should be placed outside of the M2 to C1
Exposed Pad ground path to prevent switching current spikes from inducing voltage noise into the part.
Exposed pad and GND must be connected together.
Feedback. An external resistor divider from the output to GND, tapped to the FB pin sets
the output voltage. To prevent current limit run away during a short circuit fault condition
FB
the frequency foldback comparator lowers the oscillator frequency when the FB voltage
is below 250mV.
EN/SYNC
On/Off Control and External Frequency Synchronization Input.
Supply Voltage. The MP8675 operates from a +4.5V to +42V unregulated input. C1 is
IN
needed to prevent large voltage spikes from appearing at the input.
6
7
8
MP8675 Rev.1.2
1/26/2010
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2010 MPS. All Rights Reserved.
4
MP8675 – 6A, 42V, 420KHZ STEP-DOWN WITH SYNCHRONIZABLE GATE DRIVER
TYPICAL PERFORMANCE CHARACTERISTICS
V
IN
= 12V, V
OUT
= 3.3V, L = 4.3µH, T
A
= +25ºC, unless otherwise noted.
Enable Supply Current
vs. Input Voltage
5.0
4.5
4.0
3.5
900
895
890
885
880
875
870
865
860
855
850
Disable Supply Current
vs. Input Voltage
V
CC
Regulator Line
Regulation
5.5
5.3
5.1
4.9
V
CC
(V)
3.0
2.5
2.0
1.5
1.0
0.5
0
10
20
30
40
INPUT VOLTAGE (V)
50
0
0
10
20
30
40
INPUT VOLTAGE (V)
50
4.7
4.5
4.3
4.1
3.9
3.7
3.5
0
10
20
30
40
INPUT VOLTAGE (V)
50
13
100
D
max
Limit
NORMALIZED OUTPUT VOLTAGE (%)
Peak Current vs.
Duty Cycle
OUTPUT VOLTAGE (V)
12
11
10
9
8
7
0
10
20 30
40
50
DUTY CYCLE (%)
60
Operating Range
0.15
0.10
0.05
Load Regulation
PEAK CURRENT (A)
10
420KHz
V
IN
=5V
0
- 0.05
- 0.10
- 0.15
V
IN
=12V
0
1
2
3
4
5
6
LOAD CURRENT (A)
7
V
IN
=40V
1
0.1
0
10
20
30
40
INPUT VOLTAGE (V)
50
Line Regulation
NORMALIZED OUTPUT VOLTAGE (%)
0.3
0.2
0.1
0
I
OUT
=3A
- 0.1
- 0.2
- 0.3
I
OUT
=6A
0
10
20
30
40
INPUT VOLTAGE (V)
50
40
30
I
OUT
=0A
90
80
70
60
Case Temperature vs.
Output Current
1
2
3
4
5
OUTPUT CURRENT (A)
6
MP8675 Rev.1.2
1/26/2010
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2010 MPS. All Rights Reserved.
5
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