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TM
MP2112
1MHz, 1A Synchronous Step-Down Converter
The Future of Analog IC Technology
TM
DESCRIPTION
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. The MP2112 is available in a space-saving 6-pin QFN package.
FEATURES
* * * * * * * * * * * * * * * * * 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 <0.1A 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
APPLICATIONS
"MPS" and "The Future of Analog IC Technology" are Trademarks of Monolithic Power Systems, Inc.
TYPICAL APPLICATION
VIN 2.5V to 6V
5 VINA 6 3
Efficiency vs Load Current
100 90
EN
VIN = 3.3V VIN = 4.2V
EN
EFFICIENCY (%)
80 70 60 50 40 30 20 10 0 10
MP2112
4 2 VINB SW
VOUT 1.8V/1A
GND
FB
1
MP2112_TAC_S01
100 LOAD CURRENT (mA)
1000
MP2112-EC01
MP2112 Rev. 1.2 3/6/2006
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TM
MP2112 - 1MHz, 1A SYNCHRONOUS STEP-DOWN CONVERTER
PACKAGE REFERENCE
TOP VIEW
FB 1 6 EN
ABSOLUTE MAXIMUM RATINGS (1)
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.............................+150C Lead Temperature ..................................+260C Storage Temperature .............-65C to +150C
GND
2
5
VINA
Recommended Operating Conditions
(2)
SW
3
4
VINB
EXPOSED PAD ON BACKSIDE
Supply Voltage VIN ............................. 2.5V to 6V Output Voltage VOUT .......................... 0.6V to 6V Operating Temperature .............-40C to +85C
MP2112_PD01_QFN6
Thermal Resistance
Temperature -40C to +85C
(3)
Part Number* MP2112DQ *
Package QFN6 (3mm x 3mm)
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.
JA
JC
For Tape & Reel, add suffix -Z (eg. MP2112DQ-Z) For Lead Free, add suffix -LF (eg. MP2112DQ-LF-Z)
ELECTRICAL CHARACTERISTICS (4)
VIN = VEN = 3.6V, TA = +25C, unless otherwise noted.
Parameter Supply Current Shutdown Current IN Undervoltage Lockout Threshold IN Undervoltage Lockout Hysteresis Regulated FB Voltage 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 fOSC Symbol Condition VEN = VIN, VFB = 0.65V VEN = 0V, VIN = 6V Rising Edge Min Typ 440 0.10 2.30 55 VFB TA = +25C -40C TA +85C VFB = 0.65V ISW = 100mA ISW = -100mA VEN = 0V, VIN = 6V, VSW = 0V or 6V Duty Cycle = 100%, Current Pulse Width < 1ms 0.588 0.582 -50 0.600 0.600 0.5 0.42 0.26 0.612 0.618 +50 Max 600 1 2.40 Units A A V mV V nA A A MHz C 1.5 1 V A
2.15
-1 1.2 0.85 1.6 1.05 145
+1 2.1 1.25
-40C TA +85C VIN = 0V to 6V
0.3 -1
0.96
Note: 4) 100% production test at +25C. Specifications over the temperature range are guaranteed by design and characterization.
MP2112 Rev. 1.2 3/6/2006
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TM
MP2112 - 1MHz, 1A SYNCHRONOUS STEP-DOWN CONVERTER
PIN FUNCTIONS
Pin # 1 2 3 4 5 6 Name Description FB 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 = 4.7H, C1 = 4.7F, C3 = 10F, TA = +25C, unless otherwise noted.
100 95 90
VIN=3.3V
95 90 VIN=4.2V VIN=3.3V VIN=4.2V 85 80 75 70 65 60 55 50
EFFICIENCY (%)
85 80 75 70 65 60 55 50 10
100 LOAD CURRENT (mA)
1000
EFFICIENCY (%)
10
100 LOAD CURRENT (mA)
1000
MP2112-EC01
MP2112-EC02
Feedback Voltage vs Temperature
SWITCHING FREQUENCY (MHz)
0.603
Switching Frequency vs Temperature
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-TPC04
FEEDBACK VOLTAGE (V)
0.602 0.601 0.600 0.599 0.598 0.597 -40 -20 0 +20 +40 +60 +80 +100 TEMPERATURE (C)
MP2112-TPC03
MP2112 Rev. 1.2 3/6/2006
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TM
MP2112 - 1MHz, 1A SYNCHRONOUS STEP-DOWN CONVERTER
TYPCIAL PERFORMANCE CHARACTERISTICS (continued)
VIN = 3.3V, VOUT = 1.8V, L1 = 4.7H, C1 = 4.7F, C3 = 10F, TA = +25C, unless otherwise noted.
Load Transient
(IOUT=0mA to 500mA step) VOUT 10mV/div. IL 0.2A/div.
No Load Operation
VOUT 100mV/div.
IOUT 0.5A/div.
SW 2V/div.
MP2112-TPC05
MP2112-TPC06
Heavy Load Operation
VOUT 10mV/div. IL 0.2A/div.
Startup from Shutdown
VEN 2V/div. VOUT 1V/div.
SW 2V/div.
IL=0
IL 0.5A/div.
MP2112-TPC07
MP2112-TPC08
Short Circuit Protection (No Load)
VOUT 1V/div. VOUT 1V/div.
Short Circuit Recovery (No Load)
IL 0.5A/div.
IL 0.5A/div.
MP2112-TPC09
MP2112-TPC10
MP2112 Rev. 1.2 3/6/2006
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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
VINA/VINB + IAMP 10X -CURRENT SENSE AMP PWM DH MAIN SWITCH (PCH) PWM CONTROL LOGIC SW SYNCHRONOUS RECTIFIER (NCH) DL
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 x fOSC x 100% VOUT x 100% VIN
where TON is the main switch on time, and fOSC is the oscillator frequency (1MHz).
EN
BIAS & VOLTAGE REFERENCE ICS SLOPE COMP EAO
0.6V + FEEDBACK ERROR\ EAMP AMP --
+ + PWMCMP --
FB
CC 17pF
1.0MHz OSCILLATOR
OSC
GND
MP2112_BD01
Figure 1--Functional Block Diagram
MP2112 Rev. 1.2 3/6/2006
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TM
MP2112 - 1MHz, 1A SYNCHRONOUS STEP-DOWN CONVERTER 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.
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
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 500k for optimal transient response. R2 is then given by:
R2 = R1 VOUT -1 0 .6 V
Inductor Selection A 1H to 10H 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 <200m. See Table 2 for recommended inductors and manufacturers. For most designs, the inductance value can be derived from the following equation:
L1 = VOUT x (VIN - VOUT ) VIN x IL x fOSC
Table 1--Resistor Selection vs. Output Voltage Setting
VOUT 1.2V 1.5V 1.8V 2.5V R1 499k (1%) 499k (1%) 499k (1%) 499k (1%) R2 499k (1%) 332k (1%) 249k (1%) 158k (1%)
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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MP2112 Rev. 1.2 3/6/2006
www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2006 MPS. All Rights Reserved.
TM
MP2112 - 1MHz, 1A SYNCHRONOUS STEP-DOWN CONVERTER
Table 2--Suggested Surface Mount Inductors
Manufacturer
Coilcraft Toko Sumida
Part Number
D63CB D53LC CDC5D23B
Inductance (H)
4.7 4.7 4.7
Max DCR ()
0.026 0.026 0.062
Saturation Current (A)
2.0 2.0 1.6
Dimensions LxWxH (mm3)
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
Coilcraft Murata Sumida Sumida
Part Number
DO1605T-103MX LQH4C100K04 CR32-100 CR54-100
Inductance (H)
10 10 10 10
Max DCR ()
0.3 0.2 0.2 0.1
Saturation Current (A)
1.0 1.2 1.0 1.2
IRMS (A)
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 4.7F capacitor is sufficient.
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 x (VIN - VOUT ) 1 x ESR + VIN x f OSC x L 8 x f OSC x C2
MP2112 Rev. 1.2 3/6/2006
www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2006 MPS. All Rights Reserved.
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TM
MP2112 - 1MHz, 1A SYNCHRONOUS STEP-DOWN CONVERTER
PACKAGE INFORMATION
QFN6 (3mm x 3mm)
2.90 3.10 PIN 1 ID MARKING 0.35 0.45 2.90 3.10 0.95 BSC 4 3 0.35 0.55 1.40 1.60 PIN 1 ID SEE DETAIL A 1
6
PIN 1 ID INDEX AREA
2.20 2.40
TOP VIEW
BOTTOM VIEW
PIN 1 ID OPTION A R0.20 TYP. 0.20 REF 0.00 0.05 0.80 1.00
PIN 1 ID OPTION B R0.20 TYP.
SIDE VIEW
DETAIL A
2.90 0.80 1.50
NOTE:
1) 2) 3) 4) 5) 2.30 ALL DIMENSIONS ARE IN MILLIMETERS . EXPOSED PADDLE SIZE DOES NOT INCLUDE MOLD FLASH . LEAD COPLANARITY SHALL BE 0.10 MILLIMETER MAX . JEDEC REFERENCE IS MO -229, VARIATION VEEA-2. DRAWING IS NOT TO SCALE .
0.40
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. (c) 2006 MPS. All Rights Reserved.
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