MPS MP2259 1a, 16v, 1.4mhz step-down converter Datasheet

MP2259
1A, 16V, 1.4MHz
Step-Down Converter
The Future of Analog IC Technology
FEATURES
DESCRIPTION
The MP2259 is a monolithic integrated stepdown switch mode converter with an internal
power MOSFET. It achieves 1A 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 MP2259 requires a minimum number of
readily available standard external components.
The MP2259 is available in TSOT23-6 and
SOT23-6 packages.
•
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•
•
•
•
•
•
•
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1A Output Current
0.5Ω Internal Power MOSFET Switch
Stable with Low ESR Output Ceramic
Capacitors
Up to 92% Efficiency
0.1μA Shutdown Mode
Fixed 1.4MHz Frequency
Thermal Shutdown
Cycle-by-Cycle Over Current Protection
Wide 4.5V to 16V Operating Input Range
Output Adjustable from 0.81V to 14V
Available in TSOT23-6 and SOT23-6 Packages
APPLICATIONS
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Hand Disk Drive
xDSL Modems Cable
Set-Top Box
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Monolithic Power Systems, Inc.
TYPICAL APPLICATION
Efficiency vs
Load Current
5
IN
BST
12V
4
EN
GND
2
SW
6
D1
B230A
FB
3
VOUT = 5V
95
CB
10nF
MP2259
OFF ON
100
1
90
VOUT
3.3V @ 1A
EFFICIENCY (%)
VIN
85
80
VOUT = 3.3V
75
70
65
60
VIN = 12V
55
50
10
100
1000
LOAD CURRENT (mA)
MP2259-EC01
MP2259 Rev. 0.92
9/15/2011
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1
MP2259 – 1A, 16V, 1.4MHz STEP-DOWN CONVERTER
ORDERING INFORMATION
Part Number
Package
Top Marking
Temperature
MP2259DJ*
TSOT23-6
J9
–40°C to +85°C
Part Number
Package
Top Marking
Temperature
MP2259DT**
SOT23-6
K1
–40°C to +85°C
* For Tape & Reel, add suffix –Z (eg. MP2259DJ–Z);
For RoHS compliant packaging, add suffix –LF. (eg. MP2259DJ–LF–Z)
* * For Tape & Reel, add suffix –Z (eg. MP2259DT–Z);
For RoHS compliant packaging, add suffix –LF (eg. MP2259DT–LF–Z)
PACKAGE REFERENCE
TOP VIEW
TOP VIEW
BST
1
6
SW
BST
1
6
SW
GND
2
5
IN
GND
2
5
IN
FB
3
4
EN
FB
3
4
EN
MP2259_PD01_TSOT23
MP2259_PD02_SOT23
TSOT23-6
SOT23-6
ABSOLUTE MAXIMUM RATINGS (1)
Thermal Resistance
Supply Voltage VIN ....................................... 20V
VSW ............................................................... 21V
VBS ....................................................... VSW + 6V
All Other Pins .................................–0.3V to +6V
Continuous Power Dissipation
(TA = +25°C)(2)
TSOT23-6 ................................................ 0.57W
SOT23-6 .................................................. 0.57W
Junction Temperature ...............................150°C
Lead Temperature ....................................260°C
Storage Temperature.............. –65°C to +150°C
TSOT23-6.............................. 220 .... 110.. °C/W
SOT23-6 ................................ 220 .... 110.. °C/W
Recommended Operating Conditions
(3)
Supply Voltage VIN ...........................4.5V to 16V
Output Voltage VOUT ......................... 0.81 to 14V
Maximum Junction Temp. (TJ) .............. +125°C
MP2259 Rev. 0.92
9/15/2011
(4)
θJA
θJC
Notes:
1) Exceeding these ratings may damage the device.
2) The maximum allowable power dissipation is a function of the
maximum junction temperature TJ(MAX), the junction-toambient thermal resistance θJA, and the ambient temperature
TA. The maximum allowable continuous power dissipation at
any ambient temperature is calculated by PD(MAX)=(TJ(MAX)TA)/ θJA. 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.
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2
MP2259 – 1A, 16V, 1.4MHz STEP-DOWN CONVERTER
ELECTRICAL CHARACTERISTICS
VIN = 12V, TA = +25°C, unless otherwise noted.
Parameters
Symbol Condition
Feedback Voltage
VFB
Feedback Current
IFB
Switch-On Resistance
Switch Leakage
4.5V ≤ VIN ≤ 16V
VFB = 0.8V
VFB = 2V
Min
Typ
Max
Units
0.790
0.810
0.830
V
10
nA
µA
Ω
μA
10
2
0.5
RDS(ON)
VEN = 0V, VSW = 0V
Current Limit (5)
Oscillator Frequency
Fold-back Frequency
Maximum Duty Cycle
Minimum On-Time
Under Voltage Lockout Threshold Rising
Under Voltage Lockout Threshold Hysteresis
EN Input Low Voltage
En Input High Voltage
fSW
VFB = 0.6V
VFB = 0V
VFB = 0.6V
tON
EN Input Current
Supply Current (Shutdown)
Supply Current (Quiescent)
Thermal Shutdown
2.5
1.8
A
1.4
460
85
100
2.8
200
MHz
KHz
%
ns
V
mV
V
V
3.1
0.4
VEN = 5V
VEN = 0V
VEN = 0V
VEN = 2V, VFB = 1V
1.2
3
-1
7
1
0.1
1.0
150
μA
μA
mA
°C
Note:
5) Slope compensation changes current limit above 40% duty cycle.
PIN FUNCTIONS
Pin #
Name Description
1
BST
2
GND
3
FB
4
EN
5
IN
6
SW
MP2259 Rev. 0.92
9/15/2011
Bootstrap. This capacitor is needed to drive the power switch’s gate above the supply voltage. It
is connected between SW and BS pins to form a floating supply across the power switch driver.
Ground. This pin is the voltage reference for the regulated output voltage. For this reason care
must be taken in its layout. This node should be placed outside of the D1 to C1 ground path to
prevent switching current spikes from inducing voltage noise into the part.
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 the
frequency foldback comparator lowers the oscillator frequency when the FB voltage is below
250mV.
On/Off Control Input. Pull above 1.2V to turn the device on.
Supply Voltage. The MP2259 operates from a +4.5V to +16V unregulated input. C1 is needed
to prevent large voltage spikes from appearing at the input.
Switch Output.
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3
MP2259 – 1A, 16V, 1.4MHz STEP-DOWN CONVERTER
TYPICAL PERFORMANCE CHARACTERISTICS
VIN = 12V, VOUT = 3.3V, L = 4.7µH, C1 = 10µF, C2 = 22µF, TA = +25ºC, unless otherwise noted.
Current Limit vs
Duty Cycle
Steady State Test
IOUT = 0.5A
3.0
CURRENT LIMIT (A)
2.5
VOUT
20mV/div.
VOUT
AC Coupled
50mV/div.
2.0
1.5
1.0
IL
500mA/div.
ILOAD
1A/div.
0.5
0
VSW
10V/div.
IL
1A/div.
0
20
40
60
80
DUTY CYCLE (%)
400ns/div.
100
Short Circuit Entry
Short Circuit Recovery
Start-up through Enable
No Load
VEN
5V/div.
VOUT
1V/div.
VOUT
1V/div.
IL
1A/div.
VOUT
1V/div.
VSW
10V/div.
IL
500mA/div.
IL
1A/div.
Shut-down through Enable
Start-up through Enable
VEN
5V/div.
VEN
5V/div.
VOUT
2V/div.
IL
1A/div.
MP2259 Rev. 0.92
9/15/2011
IOUT = 1A Resistive Load
VEN
5V/div.
VOUT
2V/div.
VOUT
1V/div.
VSW
10V/div.
Shut-down through Enable
No Load
IOUT = 1A Resistive Load
VSW
10V/div.
IL
1A/div.
VSW
10V/div.
IL
1A/div.
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4
MP2259 – 1A, 16V, 1.4MHz STEP-DOWN CONVERTER
OPERATION
The MP2259 is a current mode buck regulator.
with EA output voltage proportional to the peak
inductor current.
At the beginning of a cycle, M1 is off. The EA
output voltage is higher than the current sense
amplifier output, and the current comparator’s
output is low. The rising edge of the 1.4MHz
CLK signal sets the RS Flip-Flop. Its output
turns on M1 then connects the SW pin and
inductor to the input supply.
The increasing inductor current is sensed and
amplified by the Current Sense Amplifier. Ramp
compensation is summed to Current Sense
Amplifier output and compared to the Error
Amplifier output by the PWM Comparator.
When the sum of the Current Sense Amplifier
output and the Slope Compensation signal
exceeds the EA output voltage, the RS FlipFlop is reset and M1 is turned off. The external
Schottky rectifier diode (D1) conducts the
inductor current.
If the sum of the Current Sense Amplifier output
and the Slope Compensation signal does not
exceed the EA output for a whole cycle, then
the falling edge of the CLK resets the Flip-Flop.
The output of the Error Amplifier integrates the
voltage difference between the feedback and
the 0.8V bandgap reference. The polarity is
such that a FB pin voltage lower than 0.8V
increases the EA output voltage. Since the EA
output voltage is proportional to the peak
inductor current, an increase in its voltage
increases current delivered to the output.
IN 5
CURRENT SENSE
AMPLIFIER
+
--
x20
REGULATOR
EN 4
REGULATOR
OSCILLATOR
1.4MHz
S
+
-1pF
REFERENCE
FB 3
Q
1
BST
6
SW
M1
DRIVER
R
CURRENT
LIMIT
COMPARATOR
R
27pF
+EA
--
ERROR
AMPLIFIER
+
--
PWM
COMPARATOR
GND 2
MP2259_F01_BD01
Figure 1—Functional Block Diagram
MP2259 Rev. 0.92
9/15/2011
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© 2011 MPS. All Rights Reserved.
5
MP2259 – 1A, 16V, 1.4MHz STEP-DOWN CONVERTER
APPLICATION INFORMATION
Setting the Output Voltage
The external resistor divider is used to set the
output voltage (see the schematic on front
page). The feedback resistor R1 also sets the
feedback loop bandwidth with the internal
compensation capacitor (see Figure 1). R2 can
be determined by:
R2 =
R1
VOUT
−1
0.81V
Table 1—Resistor Selection for Common
Output Voltages
VOUT (V)
R1 (kΩ)
R2 (kΩ)
1.8
2.5
3.3
5
80.6 (1%)
49.9 (1%)
49.9 (1%)
49.9 (1%)
64.9 (1%)
23.7 (1%)
16.2 (1%)
9.53 (1%)
Selecting the Inductor
A 1µH to 10µH inductor is recommended for
most applications. For highest efficiency, the
inductor’s DC resistance should be less than
200mΩ. For most designs, the required
inductance value can be derived from the
following equation:
L=
VOUT × ( VIN − VOUT )
VIN × ΔIL × f OSC
Where ΔIL is the inductor ripple current.
Choose an inductor with a rating current higher
than the maximum load current. The maximum
inductor peak current can be calculated from:
IL(MAX ) = ILOAD +
ΔI L
2
with X5R or X7R dielectrics are highly
recommended because of their low ESR and
small temperature coefficients. For most
applications, a 4.7µF capacitor is sufficient.
Selecting the Output Capacitor
The output capacitor (C2) keeps output voltage
ripple small and ensures loop stability. The
output capacitor impedance should be low at
the switching frequency. Ceramic capacitors
with X5R or X7R dielectrics are recommended
for their low ESR characteristics. A 10µF~ 22µF
capacitor is good for most applications.
PCB Layout Guide
PCB layout is very important to achieve stable
operation. Please follow these guidelines and
take Figure2 for references.
1)
Keep the path of switching current short
and minimize the loop area formed by Input
cap, high-side MOSFET and schottky diode.
2)
Keep the connection of schottky diode
between SW pin and input power ground
as short and wide as possible.
3)
Ensure all feedback connections are short
and direct. Place the feedback resistors
and compensation components as close to
the chip as possible.
4)
Route SW away from sensitive analog
areas such as FB.
5)
Connect IN, SW, and especially GND
respectively to a large copper area to cool
the chip to improve thermal performance
and long-term reliability. For single layer,
do not solder exposed pad of the IC.
Under light load conditions below 100mA, a
larger inductance is recommended for improved
efficiency.
Selecting the Input Capacitor
The input capacitor (C1) reduces the surge
current drawn from the input and the switching
noise from the device. The input capacitor
impedance at the switching frequency should
be less than the input source impedance to
prevent high frequency switching current from
passing through the input. Ceramic capacitors
MP2259 Rev. 0.92
9/15/2011
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© 2011 MPS. All Rights Reserved.
6
MP2259 – 1A, 16V, 1.4MHz STEP-DOWN CONVERTER
R2
R1
SGND
C3
1 BST SW 6
EN 4
2 GND IN 5
3 FB
R3
L1
C1
D1
C2
PGND
Figure2―PCB Layout
External Bootstrap Diode
An external bootstrap diode may enhance the
efficiency of the regulator, the applicable
conditions of external BST diode are:
z
VOUT=5V or 3.3V; and
z
Duty cycle is high: D=
VOUT
>65%
VIN
In these cases, an external BST diode is
recommended from the output of the voltage
regulator to BST pin, as shown in Fig.3
External BST Diode
IN4148
BST
CBST
MP2259
SW
L
+
COUT
5V or 3.3V
Figure 3—Add Optional External Bootstrap
Diode to Enhance Efficiency
The recommended external BST diode is
IN4148, and the BST cap is 0.1~1µF.
MP2259 Rev. 0.92
9/15/2011
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© 2011 MPS. All Rights Reserved.
7
MP2259 – 1A, 16V, 1.4MHz STEP-DOWN CONVERTER
PACKAGE INFORMATION
TSOT23-6
6
See Note 7
EXAMPLE
TOP MARK
4
AAAA
PIN 1
0.95
BSC
0.60
TYP
2.80
3.00
1
1.20
TYP
1.50
1.70
2.60
3.00
2.60
TYP
3
TOP VIEW
RECOMMENDED LAND PATTERN
0.84
0.90
1.00 MAX
0.09
0.20
SEATING PLANE
0.30
0.50
0.95 BSC
0.00
0.10
SEE DETAIL "A"
FRONT VIEW
SIDE VIEW
NOTE:
GAUGE PLANE
0.25 BSC
0o-8o
DETAIL
揂
MP2259 Rev. 0.92
9/15/2011
0.30
0.50
1) ALL DIMENSIONS ARE IN MILLIMETERS.
2) PACKAGE LENGTH DOES NOT INCLUDE MOLD FLASH
,
PROTRUSION OR GATE BURR.
3) PACKAGE WIDTH DOES NOT INCLUDE INTERLEAD FLASH
OR PROTRUSION.
4) LEAD COPLANARITY(BOTTOM OF LEADS AFTER FORMING)
SHALL BE 0.10 MILLIMETERS MAX.
5) DRAWING CONFORMS TO JEDEC MO-193, VARIATION AB.
6) DRAWING IS NOT TO SCALE.
7) PIN 1 IS LOWER LEFT PIN WHEN READING TOP MARK FROM
LEFT TO RIGHT, (SEE EXAMPLE TOP MARK)
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8
MP2259 – 1A, 16V, 1.4MHz STEP-DOWN CONVERTER
SOT23-6
6
See Note 7
EXAMPLE
TOP MARK
4
AAAA
PIN 1
0.95
BSC
0.60
TYP
2.80
3.00
1
1.20
TYP
1.50
1.70
2.60
3.00
2.60
TYP
3
TOP VIEW
RECOMMENDED LAND PATTERN
0.90
1.30
1.45 MAX
0.09
0.20
SEATING PLANE
0.30
0.50
0.95 BSC
0.00
0.15
SEE DETAIL "A"
FRONT VIEW
SIDE VIEW
NOTE:
GAUGE PLANE
0.25 BSC
0o-8o
DETAIL
揂
0.30
0.55
1) ALL DIMENSIONS ARE IN MILLIMETERS.
2) PACKAGE LENGTH DOES NOT INCLUDE MOLD FLASH
,
PROTRUSION OR GATE BURR.
3) PACKAGE WIDTH DOES NOT INCLUDE INTERLEAD FLASH
OR PROTRUSION.
4) LEAD COPLANARITY(BOTTOM OF LEADS AFTER FORMING)
SHALL BE 0.10 MILLIMETERS MAX.
5) DRAWING CONFORMS TO JEDEC MO-193, VARIATION AB.
6) DRAWING IS NOT TO SCALE.
7) PIN 1 IS LOWER LEFT PIN WHEN READING TOP MARK FROM
LEFT TO RIGHT, (SEE EXAMPLE TOP MARK)
NOTICE: The information in this document is subject to change without notice. Please contact MPS for current specifications.
Users should warrant and guarantee that third party Intellectual Property rights are not infringed upon when integrating MPS
products into any application. MPS will not assume any legal responsibility for any said applications.
MP2259 Rev. 0.92
9/15/2011
www.MonolithicPower.com
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2011 MPS. All Rights Reserved.
9
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