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TM
MP2109
Dual 1.2MHz, 800mA Synchronous Step-Down Converter
The Future of Analog IC Technology
TM
DESCRIPTION
The MP2109 contains two independent 1.2MHz constant frequency, current mode, PWM step-down converters. Each converter integrates a main switch and a synchronous rectifier for high efficiency without an external Schottky diode. The MP2109 is ideal for powering portable equipment that runs from a single cell Lithium-Ion (Li+) battery. Each converter can supply 800mA of load current from a 2.5V to 6V input voltage. The output voltage can be regulated as low as 0.6V. The MP2109 can also run at 100% duty cycle for low dropout applications.
FEATURES
* * * * * * * * * * * * * * * * * * Up to 95% Efficiency 1.2MHz Constant Switching Frequency 800mA Load Current on Each Channel 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 Internally Compensated Space Saving 10-Pin QFN Package Cellular and Smart Phones Microprocessors and DSP Core Supplies PDAs MP3 Players Digital Still and Video Cameras Portable Instruments
EVALUATION BOARD REFERENCE
Board Number EV2109DQ-00A Dimensions 1.5"X x 1.0"Y x 0.5"Z
APPLICATIONS
"MPS" and "The Future of Analog IC Technology" are Trademarks of Monolithic Power Systems, Inc.
TYPICAL APPLICATION
VIN1/IN2 2.5V to 6V
8 IN1 3 IN2 EN2 6
100 95
OFF ON
OFF ON
1
EN1
90
EFFICIENCY (%)
85 80 75 70 65 60 55 50 0
VOUT=3.3V
VOUT1 1.8V 800mA
10
SW1
MP2109
SW2
5
VOUT2 1.2V 800mA
2
FB1 GND1 9 GND2 4
FB2
7
MP2109_S01
500 LOAD CURRENT (mA)
1000
MP2109_EC01
MP2109 Rev.1.3 2/21/2006
www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2006 MPS. All Rights Reserved.
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TM
MP2109 - DUAL 1.2MHz 800mA SYNCHRONOUS STEP-DOWN CONVERTER
PACKAGE REFERENCE
TOP VIEW
EN1 FB1 IN2 GND2 SW2 1 2 3 4 5 10 9 8 7 6 SW1 GND1 IN1 FB2 EN2
ABSOLUTE MAXIMUM RATINGS (1)
VIN1/IN2 to GND ............................ -0.3V to +6.5V VSW1/SW2 to GND................... -0.3V to VIN + 0.3V VFB1/FB2, VEN1/EN2 to GND ............. -0.3V to +6.5V Junction Temperature.............................+150C Lead Temperature ..................................+260C Storage Temperature .............-65C to +150C
Recommended Operating Conditions
(2)
EXPOSED PAD ON BACKSIDE
MP2109_PD02_QFN10
Supply Voltage VIN1/IN2 ....................... 2.5V to 6V Output Voltage VOUT1/OUT2 .................. 0.6V to 6V Operating Temperature .............-40C to +85C
Thermal Resistance
Temperature -40C to +85C
(3)
Part Number* MP2109DQ *
Package QFN10 (3mm x 3mm)
QFN10 (3mm x 3mm) ............. 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. MP2109DQ-Z) For Lead Free, add suffix -LF (eg. MP2109DQ-LF-Z)
ELECTRICAL CHARACTERISTICS (4)
VIN1/IN2 = VEN1/EN2 = 3.6V, TA = +25C, unless otherwise noted.
Parameter Symbol Condition Each Converter Supply Current VEN1/EN2 = VIN1/IN2, VFB1/FB2 = 0.65V Each Converter Shutdown VEN1/EN2 = 0V, VIN1/IN2 = 6V Current IN Under Voltage Lockout Rising Edge Threshold IN Under Voltage Lockout Hysteresis TA = +25C Regulated FB Voltage VFB -40C TA +85C FB Input Bias Current IFB VFB1/FB2 = 0.65V PFET On Resistance ISW1/SW2 = 100mA NFET On Resistance ISW1/SW2 = -100mA VEN1/EN2 = 0V, VIN1/IN2 = 6V SW Leakage Current VSW1/SW2 = 0V or 6V Duty Cycle = 100%, PFET Current Limit Current Pulse Width < 1ms Oscillator Frequency fOSC Thermal Shutdown Trip Threshold EN Enable Threshold -40C TA +85C EN Input Current VEN1/EN2 = 0V to 6V Min Typ 440 0.10 2.15 2.30 55 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 0.9 0.99 1.3 1.24 150 0.3 -1 0.96
+2 1.8 1.49
Notes: 4) Production test at +25C. Specifications over the temperature range are guaranteed by design and characterization.
MP2109 Rev.1.3 2/21/2006
www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2006 MPS. All Rights Reserved.
2
TM
MP2109 - DUAL 1.2MHz 800mA SYNCHRONOUS STEP-DOWN CONVERTER
TYPICAL PERFORMANCE CHARACTERISTICS
VIN1/IN2 = 3.3V, VOUT1 = 1.8V, VOUT2 = 1.2V, L1/2 = 4.7H, CIN1/IN2 = 4.7F, COUT1/OUT2 = 10F, TA = +25C, unless otherwise noted.
Efficiency vs Load Current
100
FEEDBACK VOLTAGE (V)
0.606 VOUT1=1.8V 0.604 0.602 0.600 0.598 0.596
Feedback Voltage vs Temperature
90
EFFICIENCY (%)
80 70 60 50 0.0
VOUT2=1.2V
0.2 0.4 0.6 LOAD CURRENT (A)
0.8
0.594 -40 -20
0 +20 +40 +60 +80 +100 TEMPERATURE (C)
MP2109-TPC02
MP2109-TPC01
Load Transient
(IOUT=0mA to 500mA Step) VSW 2V/div. VOUT AC 20mV/div. IL 200mA/div.
Medium Load Operation
(IOUT=400mA)
Heavy Load Operation
(IOUT=800mA) VSW 2V/div. VOUT AC 20mV/div. IL 500mA/div.
VOUT AC 100mV/div. IL 0.5A/div. ILOAD 0.5A/div.
400ns/div
MP2109-TPC03 MP2109-TPC04
400ns/div
MP2109-TPC05
Startup from Shutdown
VEN 2V/div VOUT 1V/div VOUT 1V/div
Short Circuit Protection
(No Load)
Short Circuit Recovery
(No Load)
VOUT 1V/div
IL 0.5A/div
IL 0.5A/div
IL 0.5A/div
MP2109-TPC06
MP2109-TPC07
MP2109-TPC08
MP2109 Rev.1.3 2/21/2006
www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2006 MPS. All Rights Reserved.
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TM
MP2109 - DUAL 1.2MHz 800mA SYNCHRONOUS STEP-DOWN CONVERTER
PIN FUNCTIONS
Pin # 1 2 3 4 5 6 7 8 9 10 Name Description Channel 1 Enable Control Input. Drive EN1 above 1.5V to turn on the Channel 1. Drive EN1 below 0.3V to turn it off (shutdown current < 0.1A). Channel 1 Feedback Input. Connect FB1 to the center point of the external resistor divider. The FB1 feedback voltage is 0.6V. IN2 Channel 2 Supply Input. Bypass to GND with a 2.2F or greater ceramic capacitor. GND2 Ground 2. Channel 2 Power Switch Output. Inductor connection to drains of the internal PFET and NFET SW2 switches. Channel 2 Enable Control Input. Drive EN2 above 1.5V to turn on the Channel 2. Drive EN2 EN2 below 0.3V to turn it off (shutdown current < 0.1A). Channel 2 Feedback Input. Connect FB2 to the center point of the external resistor divider. The FB2 feedback voltage is 0.6V. IN1 Channel 1 Supply Input. Bypass to GND with a 2.2F or greater ceramic capacitor. GND1 Ground 1. Channel 1 Power Switch Output. Inductor connection to drains of the internal PFET and NFET SW1 switches. EN1
MP2109 Rev.1.3 2/21/2006
www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2006 MPS. All Rights Reserved.
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TM
MP2109 - DUAL 1.2MHz 800mA SYNCHRONOUS STEP-DOWN CONVERTER
OPERATION
IN1/ IN2 BIAS & VOLTAGE REFERENCE ICS + SLOPE COMP EAO + IAMP 10X -CURRENT SENSE AMP PWM DH MAIN SWITCH (PCH) PWM CONTROL LOGIC SW1/ SW2 SYNCHRONOUS RECTIFIER (NCH) DL
EN1/ EN2
0.6V FEEDBACK ERROR\ EAMP AMP --
+ + PWMCMP --
FB1/ FB2
CC 17pF
1.0MHz OSCILLATOR
OSC
GND1/ GND2
MP2109_BD02
Figure 1--Functional Block Diagram (Diagram represents 1/2 of the MP2109) The MP2109 has dual independent constant frequency current mode PWM step-down converters. The MP2109 is optimized for low voltage, Li-Ion battery powered applications where high efficiency and small size are critical. The MP2109 uses external resistor dividers to set two output voltages independently from 0.6V to 6V. The device integrates both main switches and synchronous rectifiers, which provides high efficiency and eliminates the need for an external Schottky diode. The MP2109 can achieve 100% duty cycle. The duty cycle D of each step-down converter is defined as:
D = TON x f OSC x 100% = VOUT x 100% VIN
Where TON is the main switch on time, fOSC is the oscillator frequency (1.2MHz), VOUT is the output voltage and VIN is the input voltage.
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 and protection of the internal main switch and synchronous rectifier. Each channel switches at a constant frequency (1.2MHz) 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, and switched off when the peak inductor current is above the error voltage. When the main switch is off, the synchronous rectifier will be turned on immediately and stay on until the next cycle starts.
MP2109 Rev.1.3 2/21/2006
www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2006 MPS. All Rights Reserved.
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TM
MP2109 - DUAL 1.2MHz 800mA SYNCHRONOUS STEP-DOWN CONVERTER Maximum Load Current The MP2109 can operate down to 2.5V input voltage, however the maximum load current decreases at lower input due to 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.
Dropout Operation Each channel of the MP2109 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 is held on continuously to deliver current to the output up to the PFET current limit. The output voltage then is the input voltage minus the voltage drop across the main switch and the inductor. Short Circuit Protection The MP2109 has short circuit protection. When any 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.
APPLICATION INFORMATION
Output Voltage Setting The external resistor divider sets the output voltage. The feedback resistor R1 also sets the feedback loop bandwidth with the internal compensation capacitor (see Figure 1). Choose R1 around 300k 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:
L= 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 300k (1%) 300k (1%) 300k (1%) 300k (1%) R2 300k (1%) 200k (1%) 150k (1%) 95.3k (1%)
Where IL is inductor ripple current. Choose inductor ripple current approximately 30% of the maximum load current, 800mA. 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.
MP2109 Rev.1.3 2/21/2006
www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2006 MPS. All Rights Reserved.
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TM
MP2109 - DUAL 1.2MHz 800mA SYNCHRONOUS STEP-DOWN CONVERTER
Table 2--Suggested Surface Mount Inductors
Manufacturer
Coilcraft Toko Sumida
Part Number
LP03310-222ML 1002AS CDRH3D16
Inductance (H)
2.2 2.2 2.2
Max DCR ()
0.15 0.11 0.072
Saturation Current (A)
1.1 1.14 1.20
Dimensions LxWxH (mm3)
3.3 x 3.3 x 1 4.6 x 4.6 x 1.2 4 x 4 x 1.8
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 reduces the surge current drawn from the input and switching noise from the device. The input capacitor impedance at the switching frequency shall 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 keeps output voltage ripple small and ensures regulation loop stable. The output capacitor impedance shall be 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 C3
Thermal Dissipation Power dissipation shall be considered when both channels of the MP2109 provide maximum 800mA output current to the loads at high ambient temperature with low input supply voltage. If the junction temperature rises above 150C, the MP2109 two channels will be shut down. The junction-to-ambient thermal resistance of the 10-pin QFN (3mm x 3mm) RJA is 50C/W. The maximum power dissipation is about 1.6W when the MP2109 is operating in a 70C ambient temperature environment.
PD MAX = 150 o C - 70 o C 50 o C / W = 1 .6 W
PC Board Layout The high current paths (GND1/GND2, IN1/IN2 and SW1/SW2) should be placed very close to the device with short, direct and wide traces. Input capacitors should be placed as close as possible to the respective IN and GND pins. The external feedback resistors shall be placed next to the FB pins. Keep the switching nodes SW1/SW2 short and away from the feedback network.
MP2109 Rev.1.3 2/21/2006
www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2006 MPS. All Rights Reserved.
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TM
MP2109 - DUAL 1.2MHz 800mA SYNCHRONOUS STEP-DOWN CONVERTER
PACKAGE INFORMATION
QFN10 (3mm x 3mm)
Pin 1 Identif ication 2.95 3.05 0.20 0.30 10 0.35 0.45 Pin 1 Identif ication R0.200TY P 1
2.95 3.05
QFN10L (3 x 3mm)
0.500 Bsc 6 5
2.35 2.000 2.45 Ref Exp. DAP
Top View
1.65 1.75 Exp. DAP
BottomView
0.85 0.95 0.0000.050
0.178 0.228
Side View
Note: 1) Dimensions arein millimeters.
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.
MP2109 Rev. 1.3 2/21/2006 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. (c) 2006 MPS. All Rights Reserved.
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