MPS MP2112 1mhz, 1a synchronous step-down converter Datasheet

TM
MP2112
1MHz, 1A Synchronous
Step-Down Converter
The Future of Analog IC Technology
TM
DESCRIPTION
FEATURES
The MP2112 is a 1MHz constant frequency,
current mode, PWM step-down converter. The
device integrates a main switch and a
synchronous rectifier for high efficiency without
an external Schottky diode. It is ideal for
powering portable equipment that powered by a
single cell Lithium-Ion (Li+) battery. The
MP2112 can supply 1A of load current from a
2.5V to 6V input voltage. The output voltage
can be regulated as low as 0.6V. The MP2112
can also run at 100% duty cycle for low dropout
applications.
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The MP2112 is available in a space-saving
6-pin QFN package.
APPLICATIONS
•
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High Efficiency: Up to 95%
1MHz Constant Switching Frequency
1A Available Load Current
2.5V to 6V Input Voltage Range
Output Voltage as Low as 0.6V
100% Duty Cycle in Dropout
Current Mode Control
Short Circuit Protection
Thermal Fault Protection
<0.1µA Shutdown Current
Space Saving 3mm x 3mm QFN6 Package
Cellular and Smart Phones
Microprocessors and DSP Core Supplies
PDAs
MP3 Players
Digital Still and Video Cameras
Portable Instruments
“MPS” and “The Future of Analog IC Technology” are Trademarks of Monolithic
Power Systems, Inc.
TYPICAL APPLICATION
Efficiency vs
Load Current
VIN
2.5V to 6V
100
VINA
EN
MP2112
4
2
VINB
GND
SW
FB
6
3
90
EN
VOUT
1.8V/1A
1
VIN = 3.3V
80
EFFICIENCY (%)
5
VIN = 4.2V
70
60
50
40
30
20
10
0
MP2112_TAC_S01
10
100
LOAD CURRENT (mA)
1000
MP2112-EC01
MP2112 Rev. 1.2
3/6/2006
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1
TM
MP2112 – 1MHz, 1A SYNCHRONOUS STEP-DOWN CONVERTER
ABSOLUTE MAXIMUM RATINGS (1)
PACKAGE REFERENCE
VIN to GND .................................. –0.3V to +6.5V
VSW to GND........................... –0.3V to VIN +0.3V
VFB, VEN to GND.......................... –0.3V to +6.5V
Junction Temperature.............................+150°C
Lead Temperature ..................................+260°C
Storage Temperature .............–65°C to +150°C
TOP VIEW
FB
1
6
EN
GND
2
5
VINA
SW
3
4
VINB
EXPOSED PAD
ON BACKSIDE
Thermal Resistance
Package
Temperature
MP2112DQ
QFN6
(3mm x 3mm)
–40°C to +85°C
For Tape & Reel, add suffix –Z (eg. MP2112DQ–Z)
For Lead Free, add suffix –LF (eg. MP2112DQ–LF–Z)
(2)
Supply Voltage VIN ............................. 2.5V to 6V
Output Voltage VOUT .......................... 0.6V to 6V
Operating Temperature .............–40°C to +85°C
MP2112_PD01_QFN6
Part Number*
*
Recommended Operating Conditions
(3)
θJA
θJC
QFN6 (3x3)............................. 50 ...... 12... °C/W
Notes:
1) Exceeding these ratings may damage the device.
2) The device is not guaranteed to function outside of its
operating conditions.
3) Measured on approximately 1” square of 1 oz copper.
ELECTRICAL CHARACTERISTICS (4)
VIN = VEN = 3.6V, TA = +25°C, unless otherwise noted.
Parameter
Supply Current
Shutdown Current
IN Undervoltage Lockout
Threshold
IN Undervoltage Lockout
Hysteresis
Regulated FB Voltage
Symbol Condition
VEN = VIN, VFB = 0.65V
VEN = 0V, VIN = 6V
Min
Typ
440
0.10
Max
600
1
Units
µA
µA
Rising Edge
2.15
2.30
2.40
V
55
VFB
FB Input Bias Current
PFET On Resistance
NFET On Resistance
SW Leakage Current
PFET Current Limit
Oscillator Frequency
Thermal Shutdown Trip
Threshold
EN Trip Threshold
EN Input Current
TA = +25°C
–40°C ≤ TA ≤ +85°C
VFB = 0.65V
ISW = 100mA
ISW = –100mA
VEN = 0V, VIN = 6V,
VSW = 0V or 6V
Duty Cycle = 100%,
Current Pulse Width < 1ms
fOSC
0.588
0.582
–50
0.600
0.600
0.5
0.42
0.26
–1
mV
0.612
0.618
+50
nA
Ω
Ω
+1
µA
1.2
1.6
2.1
A
0.85
1.05
1.25
MHz
°C
145
–40°C ≤ TA ≤ +85°C
VIN = 0V to 6V
V
0.3
–1
0.96
1.5
1
V
µA
Note:
4) 100% production test at +25°C. Specifications over the temperature range are guaranteed by design and characterization.
MP2112 Rev. 1.2
3/6/2006
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© 2006 MPS. All Rights Reserved.
2
TM
MP2112 – 1MHz, 1A SYNCHRONOUS STEP-DOWN CONVERTER
PIN FUNCTIONS
Pin #
Name Description
1
FB
2
3
4
5
6
GND
SW
VINB
VINA
EN
Feedback Input. Connect FB to the center point of the external resistor divider. The feedback
threshold voltage is 0.6V.
Ground.
Power Switch Output. Inductor connection to drains of the internal PFET and NFET switches.
Supply Input-Power.
Supply Input-Analog.
Enable Input.
TYPCIAL PERFORMANCE CHARACTERISTICS
VIN = 3.3V, VOUT = 1.8V, L1 = 4.7µH, C1 = 4.7µF, C3 = 10µF, TA = +25°C, unless otherwise noted.
100
95
95
VIN=3.3V
EFFICIENCY (%)
EFFICIENCY (%)
90
85
VIN=4.2V
80
75
70
65
85
75
70
65
60
55
55
10
100
LOAD CURRENT (mA)
50
1000
VIN=4.2V
80
60
50
VIN=3.3V
90
10
100
LOAD CURRENT (mA)
MP2112-EC01
MP2112-EC02
Switching Frequency vs
Temperature
Feedback Voltage vs
Temperature
SWITCHING FREQUENCY (MHz)
FEEDBACK VOLTAGE (V)
0.603
0.602
0.601
0.600
0.599
0.598
0.597
-40 -20
0 +20 +40 +60 +80 +100
TEMPERATURE (°C)
1.10
1.08
1.06
1.04
1.02
1.00
0.98
0.96
0.94
-40 -20
0 +20 +40 +60 +80 +100
TEMPERATURE (°C)
MP2112-TPC03
MP2112 Rev. 1.2
3/6/2006
1000
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© 2006 MPS. All Rights Reserved.
MP2112-TPC04
3
TM
MP2112 – 1MHz, 1A SYNCHRONOUS STEP-DOWN CONVERTER
TYPCIAL PERFORMANCE CHARACTERISTICS (continued)
VIN = 3.3V, VOUT = 1.8V, L1 = 4.7µH, C1 = 4.7µF, C3 = 10µF, TA = +25°C, unless otherwise noted.
Load Transient
No Load Operation
(IOUT=0mA to 500mA step)
VOUT
10mV/div.
VOUT
100mV/div.
IL
0.2A/div.
IOUT
0.5A/div.
SW
2V/div.
MP2112-TPC05
MP2112-TPC06
Heavy Load Operation
Startup from Shutdown
VOUT
10mV/div.
VEN
2V/div.
IL
0.2A/div.
VOUT
1V/div.
SW
2V/div.
IL
0.5A/div.
IL=0
MP2112-TPC07
MP2112-TPC08
Short Circuit Protection
(No Load)
VOUT
1V/div.
Short Circuit Recovery
(No Load)
VOUT
1V/div.
IL
0.5A/div.
IL
0.5A/div.
MP2112-TPC09
MP2112 Rev. 1.2
3/6/2006
www.MonolithicPower.com
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© 2006 MPS. All Rights Reserved.
MP2112-TPC10
4
TM
MP2112 – 1MHz, 1A SYNCHRONOUS STEP-DOWN CONVERTER
OPERATION
The MP2112 is a constant frequency current
mode PWM step-down converter. The MP2112
is optimized for low voltage, Li-Ion battery
powered applications where high efficiency and
small size are critical. The MP2112 uses an
external resistor divider to set the output
voltage from 0.6V to 6V. The device integrates
both a main switch and a synchronous rectifier,
which provides high efficiency and eliminates
an external Schottky diode. The MP2112 can
achieve 100% duty cycle. The duty cycle D of a
step-down converter is defined as:
D = TON × fOSC × 100% ≈
VOUT
× 100%
VIN
where TON is the main switch on time, and fOSC
is the oscillator frequency (1MHz).
VINA/VINB
EN
ICS
0.6V
FB
+
IAMP
10X
-CURRENT
SENSE
AMP
BIAS
&
VOLTAGE
REFERENCE
+
FEEDBACK
ERROR\ EAMP
AMP
--
CC
17pF
SLOPE COMP
EAO
+
+ PWMCMP
PWM
DH
MAIN
SWITCH
(PCH)
--
1.0MHz
OSCILLATOR
OSC
PWM
CONTROL
LOGIC
SW
SYNCHRONOUS
RECTIFIER
(NCH)
DL
GND
MP2112_BD01
Figure 1—Functional Block Diagram
MP2112 Rev. 1.2
3/6/2006
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© 2006 MPS. All Rights Reserved.
5
TM
MP2112 – 1MHz, 1A SYNCHRONOUS STEP-DOWN CONVERTER
Current Mode PWM Control
Slope compensated current mode PWM control
provides stable switching and cycle-by-cycle
current limit for superior load and line response.
This protects the internal main switch and
synchronous rectifier. The MP2112 switches at a
constant frequency (1MHz) and regulates the
output voltage. During each cycle the PWM
comparator modulates the power transferred to the
load by changing the inductor peak current based
on the feedback error voltage. During normal
operation, the main switch is turned on for a certain
time to ramp the inductor current at each rising
edge of the internal oscillator, then switched off
when the peak inductor current rises above the
error voltage. When the main switch is off, the
synchronous rectifier will turn on immediately and
stay on until the next cycle starts.
Dropout Operation
The MP2112 allows the main switch to remain on
for more than one switching cycle and increases
the duty cycle while the input voltage is dropping
close to the output voltage. When the duty cycle
reaches 100%, the main switch continuously
delivers current to the output up to the PFET
current limit. The output voltage is the input
voltage minus the voltage drop across the main
switch and the inductor.
Short Circuit Protection
The MP2112 has short circuit protection. When
the output is shorted to ground, the oscillator
frequency is reduced to prevent the inductor
current from increasing beyond the PFET current
limit. The PFET current limit is also reduced to
lower the short circuit current. The frequency and
current limit will return to the normal values once
the short circuit condition is removed and the
feedback voltage reaches 0.6V.
Maximum Load Current
The MP2112 can operate down to a 2.5V input
voltage; however the maximum load current
decreases at lower input due to a large IR drop on
the main switch and synchronous rectifier. The
slope compensation signal reduces the peak
inductor current as a function of the duty cycle to
prevent sub-harmonic oscillations at duty cycles
greater than 50%. Conversely the current limit
increases as the duty cycle decreases.
APPLICATION INFORMATION
Output Voltage Setting
The external resistor divider sets the output
voltage (see Typical Application Circuit on page
1). The feedback resistor (R1) also sets the
feedback loop bandwidth with the internal
compensation capacitor (see Typical Application
Circuit).
Choose R1 around 500kΩ for optimal transient
response. R2 is then given by:
R2 =
L1 =
R1
VOUT
−1
0 .6 V
Table 1—Resistor Selection vs. Output
Voltage Setting
VOUT
R1
R2
1.2V
499kΩ (1%)
499kΩ (1%)
1.5V
499kΩ (1%)
332kΩ (1%)
1.8V
499kΩ (1%)
249kΩ (1%)
2.5V
499kΩ (1%)
158kΩ (1%)
MP2112 Rev. 1.2
3/6/2006
Inductor Selection
A 1µH to 10µH inductor with DC current rating
at least 25% higher than the maximum load
current is recommended for most applications.
For best efficiency, the inductor DC resistance
shall be <200mΩ. See Table 2 for
recommended inductors and manufacturers.
For most designs, the inductance value can be
derived from the following equation:
VOUT × (VIN − VOUT )
VIN × ∆IL × fOSC
where ∆IL is the Inductor Ripple Current.
Choose inductor ripple current approximately
30% of the maximum load current, 1A.
The maximum inductor peak current is:
IL(MAX ) = ILOAD +
∆IL
2
Under light load conditions below 100mA, larger
inductance is recommended for improved
efficiency. Table 3 lists inductors recommended
for this purpose.
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© 2006 MPS. All Rights Reserved.
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TM
MP2112 – 1MHz, 1A SYNCHRONOUS STEP-DOWN CONVERTER
Table 2—Suggested Surface Mount Inductors
Manufacturer
Part Number
Inductance (µH)
Max DCR (Ω)
Saturation
Current (A)
Dimensions
LxWxH (mm3)
Coilcraft
Toko
Sumida
D63CB
D53LC
CDC5D23B
4.7
4.7
4.7
0.026
0.026
0.062
2.0
2.0
1.6
6.3X6.3X3.5
6.3X6.3X3.5
6.0X6.0X2.5
Table 3—Inductors for Improved Efficiency at 25mA, 50mA, under 100mA Load.
Manufacturer
Part Number
Inductance (µH)
Max DCR (Ω)
Saturation
Current (A)
IRMS (A)
Coilcraft
Murata
Sumida
Sumida
DO1605T-103MX
LQH4C100K04
CR32-100
CR54-100
10
10
10
10
0.3
0.2
0.2
0.1
1.0
1.2
1.0
1.2
0.9
0.8
0.7
1.4
Input Capacitor Selection
The input capacitor (C1) reduces the surge
current drawn from the input and switching
noise from the device. The input capacitor
impedance at the switching frequency must be
less than input source impedance to prevent
high frequency switching current passing to the
input. Ceramic capacitors 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.
MP2112 Rev. 1.2
3/6/2006
Output Capacitor Selection
The output capacitor (C2) keeps output voltage
ripple small and ensures regulation loop stable.
The output capacitor impedance should remain
low at the switching frequency. Ceramic
capacitors with X5R or X7R dielectrics are
recommended. The output ripple ∆VOUT is
approximately:
∆VOUT ≤
⎞
VOUT × (VIN − VOUT ) ⎛
1
⎟
× ⎜⎜ ESR +
VIN × f OSC × L
8 × f OSC × C2 ⎟⎠
⎝
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© 2006 MPS. All Rights Reserved.
7
TM
MP2112 – 1MHz, 1A SYNCHRONOUS STEP-DOWN CONVERTER
PACKAGE INFORMATION
QFN6 (3mm x 3mm)
2.90
3.10
0.35
0.55
PIN 1 ID
MARKING
0.35
0.45
1.40
1.60
PIN 1 ID
SEE DETAIL A
1
6
2.90
3.10
PIN 1 ID
INDEX AREA
2.20
2.40
0.95
BSC
3
4
TOP VIEW
BOTTOM VIEW
PIN 1 ID OPTION A
R0.20 TYP.
PIN 1 ID OPTION B
R0.20 TYP.
0.80
1.00
0.20 REF
0.00
0.05
SIDE VIEW
DETAIL A
NOTE:
2.90
0.80
1)
2)
3)
4)
5)
1.50
0.40
ALL DIMENSIONS ARE IN MILLIMETERS.
EXPOSED PADDLE SIZE DOES NOT INCLUDE MOLD FLASH.
LEAD COPLANARITY SHALL BE0.10 MILLIMETER MAX.
JEDEC REFERENCE IS MO-229, VARIATION VEEA-2.
DRAWING IS NOT TO SCALE.
2.30
0.95
RECOMMENDED LAND PATTERN
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.
MP2112 Rev. 1.2
3/6/2006
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2006 MPS. All Rights Reserved.
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