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MIC33050
4MHz Internal Inductor PWM Buck Regulator with HyperLight LoadTM
General Description
Features
The Micrel MIC33050 is a high efficiency 500mA PWM HyperLight LoadTM * Input voltage: 2.7V to 5.5V synchronous buck (step-down) regulator with internal * 500mA output current inductor featuring HyperLight LoadTM, a patent-pending * Fixed output voltage options from 0.72V to 2.5V switching scheme that offers best-in-class light load * No external inductor required efficiency and transient performance while providing very * Ultra fast transient response small external components and low output ripple at all * 20A typical quiescent current loads. * 4MHz in PWM in constant current mode The MIC33050 also has a very low typical quiescent * Low voltage output ripple current draw of 20A and can achieve over 83% efficiency - 25mVpp in HyperLight LoadTM mode even at 1mA. - 3mV output voltage ripple in full PWM mode In contrast to traditional light load schemes, the HyperLight * >93% efficiency LoadTM architecture does need not trade off control speed to obtain low standby currents and in doing so, the device * >83% at 1mA only needs a small output capacitor to absorb the load * Micropower shutdown transient as the powered device goes from light load to full * 3mm x 3mm MLF(R)-12L load. * -40C to +125C junction temperature range At higher loads, the MIC33050 provides a constant switching frequency of greater than 4MHz while providing Applications peak efficiencies greater than 93%. The MIC33050 comes in fixed output voltage options from * Cellular phones 0.72V to 2.5V thereby eliminating external feedback * Digital cameras components. * Portable media players The MIC33050 is available in an 12-pin 3mm x 3mm MLF(R) * Wireless LAN cards with a junction operating range of -40C to +125C. * WiFi/WiMax/WiBro modules Data sheets and support documentation can be found on * USB Powered Devices Micrel's web site at: www.micrel.com. ____________________________________________________________________________________________________________
Typical Application
HyperLight Load is a trademark of Micrel, Inc. MLF and MicroLeadFrame are registered trademarks of Amkor Technology, 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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MIC33050
Ordering Information
Part Number MIC33050-4YHL MIC33050-GYHL
Note: 1. Other voltage options available. Contact Micrel for details.
Voltage 1.2V 1.8V
Temperature Range -40 to +125C -40 to +125C
Package 12-Pin 3mm x 3mm MLF
(R)
Lead Finish Pb-Free Pb-Free
12-Pin 3mm x 3mm MLF(R)
Pin Configuration
12-Pin 3mm x 3mm MLF(R) (ML)
Pin Description
Pin Number 1 9 10 Pin Name VIN EN SNS Pin Function Supply Voltage (Input): Requires bypass capacitor-to-GND. Enable (Input): Logic low will shut down the device, reducing the quiescent current to less than 4A. Input to the error amplifier, connect to the external resistor divider network to set the output voltage. For fixed output voltages connect to VOUT and an internal resistor network sets the output voltage. Feed forward Capacitor connected to Out sense pin Power Ground Analog ground Switch (Output): Internal power MOSFET output switches. Output after the internal inductor
11 2 12 3,4,5,6 7,8
CFF PGND AGND SW OUT
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Absolute Maximum Ratings(1)
Supply Voltage (VIN) .........................................................6V Output Switch Voltage (VSW) ............................................6V Output Switch Current (ISW)..............................................2A Logic Input Voltage (VEN) .................................. -0.3V to VIN Storage Temperature Range (Ts)..............-65C to +150C ESD Rating(3) .................................................................. 3kV
Operating Ratings(2)
Supply Voltage (VIN)......................................... 2.7V to 5.5V Logic Input Voltage (VEN)..............................-0.3V to VIN Junction Temperature (TJ) ..................-40C TJ +125C Thermal Resistance 3mm x 3mm MLF(R)-12 (JA)................................60C/W
Electrical Characteristics(4)
TA = 25C with VIN = VEN = 3.6V; CFF = 560pF; COUT = 4.7F; IOUT = 20mA unless otherwise specified. Bold values indicate -40C< TJ < +125C.
Parameter Supply Voltage Range Under-Voltage Lockout Threshold UVLO Hysteresis Quiescent Current, Hyper LL mode Shutdown Current Output Voltage Accuracy Current Limit in PWM Mode Output Voltage Line Regulation Output Voltage Load Regulation Maximum Duty Cycle PWM Switch ON-Resistance Frequency Soft Start Time Enable Threshold Enable Hysteresis Enable Input Current Over-temperature Shutdown Over-temperature Shutdown Hysteresis Condition (turn-on) IOUT = 0mA , VSNS > 1.2*VOUT nominal VIN = 5.5V; VEN = 0V; VIN = 3.0V, ILOAD = 20mA SNS = 0.9*VNOM VIN = 3.0V to 5.5V, ILOAD = 20mA 20mA < ILOAD < 500mA, SNS VNOM ISW = 100mA PMOS ISW = -100mA NMOS ILOAD = 120mA VOUT = 90% (turn-on) Min 2.7 2.45 Typ 2.55 100 20 0.01 -2.5 0.65 1 0.5 0.3 89 0.45 0.5 4 650 0.8 35 0.1 165 20 32 4 +2.5 1.7 Max 5.5 2.65 Units V V mV A A % A %/V % % MHz s V mV A C C
80
3.4 0.5
4.6 1.2 2
Notes: 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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Typical Characteristics
40
Quiescent Current vs. Temperature
50 45 40 35 30 25 20 15
Quiescent Current vs. Input Voltage
5.5 5.0 4.5 4.0 3.5
Switching Frequency vs. Temperature
30
20
10 VIN = 3.6V VOUT = 1.8V 20 40 60 80 TEMPERATURE (C)
10 5 0 2.7
VOUT = 1.8V No Load 3.2 3.7 4.2 4.7 5.2 INPUT VOLTAGE (V)
3.0 2.5
0
VIN = 3.6V VOUT = 1.8V Load = 150mA 20 40 60 80 TEMPERATURE (C)
5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.7
Switching Frequency vs. Input Voltage
0.80 0.78 0.76 0.74 0.72 0.70 0.68 0.66 0.64 0.62 0.60
Feedback Voltage vs. Temperature
1.90
Output Voltage vs. Temperature
1.85
1.80
VOUT = 1.8V Load = 150mA 3.2 3.7 4.2 4.7 5.2 INPUT VOLTAGE (V)
VIN = 3.6V VOUT = 1.8V No Load 20 40 60 80 TEMPERATURE (C)
1.75
1.70
VIN = 3.6V VOUT = 1.8V No Load 20 40 60 80 TEMPERATURE (C)
1.90
Output Voltage vs. Input Voltage
1.90
Output Voltage vs. Load
1.85
1.85
1.80
1.80
1.75 Load = 20mA 3.2 3.7 4.2 4.7 5.2 INPUT VOLTAGE (V)
1.75 VIN = 3.6V 200 300 LOAD (mA)
1.70 2.7
1.70
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Functional Characteristics
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Functional Characteristics (continued)
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Functional Diagram
MIC33050 Simplified Block Diagram
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MIC33050 CFF The CFF pin is connected to the SNS pin of MIC33050 with a feed-forward capacitor of 560pF. The CFF pin itself is compared with the internal reference voltage (VREF) of the device and provides the control path to control the output. VREF is equal to 0.72V. The CFF pin is sensitive to noise and should be place away from the SW pin. Refer to the layout recommendations for details. 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 recommendations for more details. AGND Signal ground (AGND) 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 recommendations for more details.
Functional Description
VIN VIN provides power to the MOSFETs for the switch mode regulator section and to the analog supply circuitry. Due to the high switching speeds, it is recommended that a 2.2F or greater capacitor be placed close to VIN and the power ground (PGND) pin for bypassing. Refer to the layout recommendations for details. EN The enable pin (EN) controls the on and off state of the device. A high logic on the enable pin activates the regulator, while a low logic deactivates it. MIC33050 features built-in soft-start circuitry that reduces in-rush current and prevents the output voltage from overshooting at start up. SW The switch (SW) pin connects directly to the inductor and provides the switching current necessary to operate in PWM mode. Due to the high speed switching on this pin, the switch node should be routed away from sensitive nodes such as the CFF pin. OUT The output pin (OUT) is the output voltage pin following the internal inductor of the device. Connect an output filter capacitor equal to 2.2F or greater to this pin. SNS The SNS pin is needed to sense the output voltage at the output filter capacitor. In order for the control loop to monitor the output voltage accurately it is good practice to sense the output voltage at the positive side the output filter capacitor where voltage ripple is smallest.
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Applications Information
Input Capacitor A minimum of 2.2F ceramic capacitor should be placed close to the VIN pin and PGND pin for bypassing. X5R or X7R dielectrics are recommended for the input capacitor. Y5V dielectrics, aside from losing most of their capacitance over temperature, they also become resistive at high frequencies. This reduces their ability to filter out high frequency noise. Output Capacitor The MIC33050 was designed for use with a 2.2F or greater ceramic output capacitor. A low equivalent series resistance (ESR) ceramic output capacitor either X7R or X5R is recommended. Y5V and Z5U dielectric capacitors, aside from the undesirable effect of their wide variation in capacitance over temperature, become resistive at high frequencies. Compensation The MIC33050 is designed to be stable with an internal inductor with a minimum of 2.2F ceramic (X5R) output capacitor. Efficiency Considerations Efficiency is defined as the amount of useful output power, divided by the amount of power supplied.
V xI Efficiency_% = OUT OUT V xI IN IN x 100
Maintaining high efficiency serves two purposes. It reduces power dissipation in the power supply, reducing the need for heat sinks and thermal design considerations and it reduces consumption of current for battery powered applications. Reduced current draw from a battery increases the devices operating time and is critical in hand held devices. There are two types of losses in switching converters; DC losses and switching losses. DC losses are simply the power dissipation of I2R. Power is dissipated in the high side switch during the on cycle. Power loss is equal to the high side MOSFET RDSON multiplied by the Switch Current2. During the off cycle, the low side N-channel MOSFET conducts, also dissipating power. Device operating current also reduces efficiency. The product of the quiescent (operating) current and the supply voltage is another DC loss. The current required driving the gates on and off at a constant 4MHz frequency and the switching transitions make up the switching losses.
The Figure above shows an efficiency curve. From no load to 100mA, efficiency losses are dominated by quiescent current losses, gate drive and transition losses. By using the HyperLight LoadTM mode, the MIC33050 is able to maintain high efficiency at low output currents. Over 100mA, efficiency loss is dominated by MOSFET RDSON and inductor losses. Higher input supply voltages will increase the Gate-to-Source threshold on the internal MOSFETs, thereby reducing the internal RDSON. This improves efficiency by reducing DC losses in the device. All but the inductor losses are inherent to the device. In which case, inductor selection becomes increasingly critical in efficiency calculations. As the inductors are reduced in size, the DC resistance (DCR) can become quite significant. The DCR losses can be calculated as follows; L_Pd = IOUT2 x DCR From that, the loss in efficiency due to inductor resistance can be calculated as follows;
VOUT x IOUT x 100 Efficiency_Loss = 1 - V OUT x IOUT + L_Pd
Efficiency loss due to DCR is minimal at light loads and gains significance as the load is increased. Inductor selection becomes a trade-off between efficiency and size in this case.
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MIC33050 pulse frequency modulation (PFM) to regulate the output. As the output current increases, the switching frequency increases. This improves the efficiency of the MIC33050 during light load currents. As the load current increases, the MIC33050 goes into continuous conduction mode (CCM) at a constant frequency of 4MHz. The equation to calculate the load when the MIC33050 goes into continuous conduction mode may be approximated by the following formula:
(V - VOUT ) x D ILOAD = IN 2L x f
HyperLight LoadTM Mode The MIC33050 uses a minimum on and off time proprietary control loop. When the output voltage falls below the regulation threshold, the error comparator begins a switching cycle that turns the PMOS on and keeps it on for the duration of the minimum-on-time. When the output voltage is over the regulation threshold, the error comparator turns the PMOS off for a minimum-offtime. The NMOS acts as an ideal rectifier that conducts when the PMOS is off. Using a NMOS switch instead of a diode allows for lower voltage drop across the switching device when it is on. The asynchronous switching combination between the PMOS and the NMOS allows the control loop to work in discontinuous mode for light load operations. In discontinuous mode, MIC33050 works in
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MIC33050 Typical Application Circuit
Bill of Materials
Item C1, C2 C3 U1
Notes: 1. TDK: www.tdk.com 2. Murata: www.murata.com 3. Micrel, Inc: www.micrel.com
Part Number C1608X5R0J476K C1005X5R0J476K MIC33050-4YHL MIC33050-GYHL
Manufacturer TDK
(1) (2)
Description 4.7F Ceramic Capacitor, 6.3V, X5R, Size 0603 560pF Ceramic Capacitor, 6.3V, X5R, Size 0402 4MHz PWM Buck Regulator with HyperLight Load Mode
Qty 2 1 1
Murata
Micrel, Inc. (4)
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PCB Layout Recommendations
Top Layer
Bottom Layer
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Package Information
12-Pin 3mm x 3mm MLF(R) (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) 2007 Micrel, Incorporated.
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