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MIC2206
2MHz PWM Synchronous Buck Regulator with LOWQ Mode and Voltage Scaling
General Description
The Micrel MIC2206 is a high efficiency 2MHz PWM synchronous buck (step-down) regulator that features a LOWQTM LDO standby mode that draws only 18A of quiescent current. The MIC2206 allows an ultra-low noise, small size, and high efficiency solution for portable power applications. In PWM mode, the MIC2206 operates with a constant frequency 2MHz PWM control. Under light load conditions, such as in system sleep or standby modes, the PWM switching operation can be disabled to reduce switching losses. In this light load LOWQTM mode, the LDO maintains an output voltage of 1V and draws only 18A of quiescent current. The LDO mode of operation saves battery life while not introducing spurious noise and high ripple as experienced with pulse skipping or bursting mode regulators. The MIC2206 operates from 2.7V to 5.5V input and features internal power MOSFETs that can supply up to 600mA output current in PWM mode. It can operate with a maximum duty cycle of 100% for use in low-dropout conditions. The MIC2206 is available in the 3mm x 3mm MLF10L package with a junction operating range from -40C to +125C. Data sheets and support documentation can be found on Micrel's web site at www.micrel.com.
Features
* 2.7 to 5.5V supply voltage * Light load LOWQTM LDO mode 18A quiescent current Low noise, 75Vrms * 2MHz PWM mode Output current to 600mA >95% efficiency 100% maximum duty cycle * Output Voltage Scaling (1V output in LOWQ Mode) * Ultra-fast transient response * Stable with 1F ceramic output capacitor * Fully integrated MOSFET switches * Micropower shutdown * Thermal shutdown and current limit protection * Pb-free 3mm x 3mm MLF-10L package * -40C to +125C junction temperature range
Applications
* Cellular phones * PDAs * USB peripherals
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Typical Application
MIC2206
VIN AVIN
VIN Li Ion Battery
LDO SW FB
2.2H
VOUT 1.8V/600mA
CIN 4.7F 0.1F
EN
100pF
LOWQ PGND BIAS AGND
COUT 2.2F Ceramic
Fixed Output Buck Regulator with LOWQTM Mode
LOWQ is a trademark of Micrel, Inc Micrel, Inc. * 2180 Fortune Drive * San Jose, Ca 95131 * USA * tel +1 (408) 944-0800 * fax +1 (408) 474-1000 * http://www.micrel.com
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Micrel
MIC2206
Ordering Information
Part Number MIC2206-1.8YML
Note: 1. Other Voltage options available. Contact Micrel for details.
Output Voltage(1) (PWM/LDO) 1.8V/1.0V
Junction Temp. Range -40 to +125C
Package 3x3 MLF-10L
Lead Finish Pb-free
Pin Configuration
AGND 1 LDO 2 BIAS 3 AVIN 4 EP 10 PGND 9 SW 8 VIN 7 LOWQ 6 EN
FB 5
3mm x 3mm MLF-10L (ML)
Pin Description
Pin Number 1 2 3 4 5 6 Pin Name AGND LDO BIAS AVIN FB EN _____ LOWQ VIN SW PGND GND Pin Function Analog (signal) Ground. LDO Output (Output): Connect to VOUT for LDO mode operation. Internal circuit bias supply. Must be de-coupled to signal ground with a 0.1F capacitor and should not be loaded. Analog Supply Voltage (Input): Supply voltage for the analog control circuitry and LDO input power. Requires bypass capacitor to GND. Feedback. Input to the error amplifier and internal feedback resistors. Place a 100pF ceramic capacitor from FB to the output. Enable (Input). Logic low will shut down the device, reducing the quiescent current to less than 5A. Enable LDO Mode (Input): Logic low enables the internal LDO and disables the PWM operation. Logic high enables the PWM mode and disables the LDO mode. Supply Voltage (Input): Supply voltage for the internal switches and drivers. Switch (Output): Internal power MOSFET output switches. Power Ground. Ground, backside pad.
7 8 9 10 EP
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MIC2206
Absolute Maximum Ratings(1)
Supply Voltage (VIN) ............................................ +6V Output Switch Voltage (VSW) ............................... +6V Output Switch Current (ISW) ................................... 2A Logic Input Voltage (VEN,VLOWQ) .............. -0.3V to VIN Storage Temperature (Ts)................ -60C to +150C ESD Rating(3) ....................................................... 3kV
Operating Ratings(2)
Supply Voltage (VIN)............................+2.7V to +5.5V Logic Input Voltage (VEN,VLOWQ) .............. -0.3V to VIN Junction Temperature (TJ) .............. -40C to +125C Junction Thermal Resistance 3x3 MLF-10L (JA) ................................... 60C/W
Electrical Characteristics (4)
VIN = VEN = VLOWQ =3.6V; L = 2.2H; COUT = 2.2F; TA = 25C, unless noted. Bold values indicate -40C< TJ < +125C Parameter Supply Voltage Range Under-Voltage Lockout Threshold UVLO Hysteresis Quiescent Current, PWM mode Quiescent Current, LDO mode Shutdown Current [Fixed Output] Voltages Current Limit in PWM Mode Output Voltage Line Regulation Output Voltage Load Regulation, PWM Mode Output Voltage Load Regulation, LDO Mode Maximum Duty Cycle PWM Switch ONResistance Oscillator Frequency LOWQ threshold voltage LOWQ Input Current Enable Threshold Enable Input Current 0.5 VFB = 0.9 * VNOM (not switching) VLOWQ = 0V;IOUT = 0mA VEN = 0V Nominal VOUT tolerance VFB = 0.9 * VNOM VOUT > 2V; VIN = VOUT+300mV to 5.5V; ILOAD= 100mA VOUT < 2V; VIN = 2.7V to 5.5V; ILOAD= 100mA 20mA < ILOAD < 300mA 100A < ILOAD < 50mA VLOWQ = 0V VFB 0.4V ISW = 50mA VFB = 0.7VFB_NOM (High Side Switch) ISW = -50mA VFB = 1.1VFB_NOM (Low Side Switch) 1.8 0.5 100 0.4 0.4 2 0.85 0.1 0.85 0.1 2.2 1.3 2 1.3 2 -1 -2 0.75 1 0.13 0.2 0.2 0.5 0.5 (turn-on) Condition Min 2.7 2.45 2.55 100 690 18 0.1 900 29 5 +1 +2 1.85 Typ Max 5.5 2.65 Units V V mV A A A % A % % % % MHz V A V A
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MIC2206
Parameter Output Voltage Noise LDO Current Limit Over-Temperature Shutdown Over-Temperature Hysteresis
Notes:
Condition LOWQ = 0V; COUT = 2.2F, 10Hz to 100kHz LOWQ = 0V; VOUT = 0V (LDO Mode)
Min
Typ 75
Max
Units Vrms mA C C
60
120 160 20
1. Exceeding the absolute maximum rating may damage the device. 2. The device is not guaranteed to function outside its operating rating. 3. Devices are ESD sensitive. Handling precautions recommended. Human body model: 1.5k in series with 100pF. 4. Specification for packaged product only.
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MIC2206
Typical Characteristics - PWM Mode
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MIC2206
Typical Characteristics - LDO Mode
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MIC2206
Functional Diagram
VIN AVIN
6
P-Channel Current Limit
BIAS
HSD
SW PWM Control Anti-Shoot Through
LSD
VOUT
COUT N-Channel Current Limit
EN Enable and Control Logic LOWQ
Bias, UVLO, Thermal Shutdown
FB
Soft Start
EA
100pF R1 R2
1.0V LDO Block
LDO Current Limit
EA
1.0V LDO
SGND
PGND
MIC2206 Block Diagram
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MIC2206
Functional Characteristics
Load Transient PWM Mode
LowQ = VIN
Load Transient LDO Mode
LowQ = 0V
Output Voltage AC Coupled (50mV/div)
Output Current (50mV/div)
Output Voltaeg AC Coupled (10mV/div)
Output Current (20mA/div)
VOUT = 1.8V
VOUT = 1V
Time 20 s/div
Time 20 s/div
Enable Transient PWM Mode
LowQ = 0V
Enable Transient LDO Mode
LowQ = 0V
VOUT (500mV/div)
Time 40 s/div
Output Voltage (500mV/div)
Enable Voltage (500mV/div)
ENABLE (1V/div)
Time 40 s/div
PWM Waveform
Switch Node Voltage (2V/div) Output Ripple Voltage (10mV/div)
L = 2.2 H COUT = 2.2 F
Time 400s/div
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MIC2206
Functional Description
VIN VIN provides power to the MOSFETs for the switch mode regulator section, along with the current limiting sensing. Due to the high switching speeds, a 1F capacitor is recommended close to VIN and the power ground (PGND) pin for bypassing. AVIN Analog VIN (AVIN) provides power to the LDO section and the bias through an internal 6 Ohm resistor. AVIN and VIN must be tied together. Careful layout should be considered to ensure high frequency switching noise caused by VIN is reduced before reaching AVIN. LDO The LDO pin is the output of the linear regulator and should be connected to the output. In LOWQ mode (LOWQ<1.5V), the LDO provides the output voltage. In PWM mode (LOWQ>1.5V) the LDO pin is high impedance. EN The enable pin provides a logic level control of the output. In the off state, supply current of the device is greatly reduced (typically <1A). Also, in the off state, the output drive is placed in a "tri-stated" condition, where both the high side P-channel Mosfet and the low-side N-channel are in an off or non-conducting state. Do not drive the enable pin above the supply voltage. LOWQ The LOWQ pin provides a logic level control between the internal PWM mode and the low noise linear regulator mode. With LOWQ pulled low (<0.5V), quiescent current of the device is greatly reduced by switching to a low noise linear regulator mode that has a typical IQ of 18A. In linear (LDO) mode the output can deliver 60mA of current at 1.0V to the output. By placing LOWQ high (>1.5V) , this transitions the device into a constant frequency PWM buck regulator mode. This allows the device the ability to efficiently deliver up to 600mA of output current at the same output voltage. BIAS The BIAS pin supplies the power to the internal power to the control and reference circuitry. The bias is powered from AVIN through an internal 6 resistor. A small 0.1F capacitor is recommended for bypassing. FB The feedback pin (FB) provides the connection to the internal FB resistor divider. Place a small 100pF ceramic capacitor between FB and the output voltage. SW The switch (SW) pin connects directly to the inductor and provides the switching current nessasary to operate in PWM mode. Due to the high speed switching on this pin, the switch node should be routed away from sensitive nodes. PGND Power ground (PGND) is the ground path for the high current PWM mode. The current loop for the power ground should be as small as possible and separate from the Analog ground (AGND) loop. Refer to the layout considerations fro more details. SGND Signal ground (SGND) is the ground path for the biasing and control circuitry. The current loop for the signal ground should be separate from the Power ground (PGND) loop. Refer to the layout considerations for more details.
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MIC2206
Applications Information
The MIC2206 is a 600mA PWM power supply that utilizes a LOWQTM light load mode to maximize battery efficiency in light load conditions. This is achieved with a LOWQ control pin that when pulled low, shuts down all the biasing and drive current for the PWM regulator, drawing only 18A of operating current. This allows the output to be scaled down and regulated to 1.0V through the LDO output, capable of providing 60mA of output current. This method has the advantage of producing a clean, low current, ultra low noise output in LOWQTM mode. During LOWQTM mode, the SW node becomes high impedance, blocking current flow. Other methods of reducing quiescent current, such as pulse frequency modulation (PFM) or bursting techniques create large amplitude, low frequency ripple voltages that can be detrimental to system operation. When more than 60mA is required, the LOWQ pin can be forced high, causing the MIC2206 to enter PWM mode. In this case, the LDO output makes a "hand-off" to the PWM regulator. The LDO output then turns off allowing up to 600mA of current to be efficiently supplied through the PWM output to the load. Input Capacitor A minimum 1F ceramic is recommended on the VIN pin for bypassing. X5R or X7R dielectrics are recommended for the input capacitor. Y5V dielectrics lose most of their capacitance over temperature and are therefore not recommended. A minimum 1F is recommended close to the VIN and PGND pins for high frequency filtering. Smaller case size capacitors are recommended due to their lower ESR and ESL.
Output Capacitor Even though the MIC2206 is optimized for a 2.2F output capacitor, output capacitance can be varied from 1F to 4.7F. The MIC2206 utilizes type III internal compensation and utilizes an internal high frequency zero to compensate for the double pole roll off of the LC filter. For this reason, larger output capacitors can create instabilities. X5R or X7R dielectrics are recommended for the output capacitor. Y5V dielectrics lose most of their capacitance over temperature and are therefore not recommended. In addition to a 2.2F, a small 10nF is recommended close to the load for high frequency filtering. Smaller case size capacitors are recommended due to there lower ESR and ESL. Inductor Selection The MIC2206 is designed for use with a 2.2H inductor. Proper selection should ensure the inductor can handle the maximum average and peak currents required by the load. Maximum current ratings of the inductor are generally given in two methods; permissible DC current and saturation current. Permissible DC current can be rated either for a 40C temperature rise or a 10% to 20% loss in inductance. Ensure the inductor selected can handle the maximum operating current. When saturation current is specified, make sure that there is enough margin that the peak current will not saturate the inductor. Peak inductor current can be calculated as follows:
V VOUT 1 - OUT VIN = IOUT + 2x f xL
IPK
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MIC2206
MIC2206 VIN 2.7V to 5.5V C1 1F
8 4 6
VIN AVIN EN LOWQ BIAS
SW LDO
9 2
2.2H
VOUT 1.8V/600mA C3 100pF C4 2.2F
LowQ C2 10nF
7 3
FB
5
PGND AGND GND
10 1
GND
Item C1 C4 C3 C2 L1 U1
Part Number 06036D105MAT2 GRM185R60J105KE21D 06036D225MAT2 GRM188R61A225KE34 VJ0402A101KXAA 0201ZD103MAT2 GRM033R10J103KA01D LQH32CN2R2M53K CDRH2D14-2R2 MIC2206BML
Description 1F Ceramic Capacitor X5R, 6.3V 0603 1F Ceramic Capacitor X5R, 6.3V 0603 2.2F Ceramic Capacitor X5R, 10V 0603 2.2uF Ceramic Capacitor X5R, 10V 0603 100pF Ceramic Capacitor 10nF Ceramic Capacitor 6.3V 0201 10nF Ceramic Capacitor 6.3V 0201 2.2H Inductor 97m 3.2mmx2.5mmx1.55mm 2.2H Inductor 94m 3.2mmx3.2mmx1.55mm 2MHz Synchronous Buck Regulator with LOWQTM Mode
Manufacturer AVX Murata AVX Murata Vishay AVX Murata Murata Sumida Micrel Semiconductor
Qty 1 1 1 1 1 1
Notes: Sumida Tel: 408-982-9660 Murata Tel: 949-916-4000 Vishay Tel: 402-644-4218 Micrel Semiconductor Tel: 408-944-0800
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MIC2206
Package Information
10-Lead MLFTM (ML)
MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http:/www.micrel.com
The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer. Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser's use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser's own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale. (c) 2005 Micrel, Incorporated.
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