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MIC2204
Micrel
MIC2204
High-Efficiency 2MHz Synchronous Buck Converter
General Description
The Micrel MIC2204 is a high-efficiency, 2MHz PWM synchronous buck switching regulator. Power conversion efficiency of above 95% is easily obtainable over a wide range of applications. A proprietary internal compensation technique ensures stability with the smallest possible inductor and ceramic output capacitor. The MIC2204 operates from 2.3V to 5.5V input and features internal power MOSFETs that can supply over 600mA of output current with output voltages down to 1V. The MIC2204 implements a constant 2MHz pulse-width-modulation (PWM) control scheme which reduces spurious noise in sensitive RF and communication applications. Additionally, the MIC2204 can be synchronized to an external clock, or multiple MIC2204s can easily be daisy-chained with the SYNCLOCK feature. The MIC2204 has a high bandwidth loop (typ. 200kHz) which allows ultra-fast transient response times. This is very useful when powering applications that require fast dynamic responses, such as the CPU cores and RF circuitry in highperformance cellular phones and PDAs. The MIC2204 is available in 10-pin MSOP and 3mm x 3mm MLFTM-10L package options with an operating junction temperature range from -40C to 125C .
Features
* * * * * * * * * * * * * * * Input voltage range: 2.3V to 5.5V Output down to 1V/ 600mA 2MHz PWM operation Ultra-fast transient response (typical 200kHz GBW) Internal compensation All ceramic capacitors >95% efficiency Fully integrated MOSFET switches Easily synchronized to external clock SYNCLOCK feature to daisy-chain multiple 2204s <340A quiescent current Logic controlled micropower shutdown Thermal shutdown and current limit protection 10-pin MSOP and 3mmx3mm MLFTM-10L -40C to +125C junction temperature range
Applications
* * * * * * High-efficiency portable power Cellular phones PDAs 802.11 WLAN power supplies RF power supplies Li Ion battery powered applications
Typical Application
4.7H MIC2204BMM 1 2.3V to 6V SYNC_IN 3 SYNC_OUT 4 EN 5 6 7 10nF 8 2 10 9 4.7F
3.3V 500mA
100 95 90
EFFICIENCY (%)
Efficiency vs. Output Current
85 80 75 70 65 60 55 50 0
4.2VIN 3.6VIN 5VIN
3.3VOUT 100 200 300 400 500 OUTPUT CURRENT (mA)
Adjustable Output Synchronous Buck Converter
MLF and MicroLeadFrame are trademarks of Amkor Technology, Inc. Micrel, Inc. * 1849 Fortune Drive * San Jose, CA 95131 * USA * tel + 1 (408) 944-0800 * fax + 1 (408) 944-0970 * http://www.micrel.com
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Ordering Information
Part Number MIC2204BMM MIC2204YMM MIC2204BML Voltage Adjustable Adjustable Adjustable Junction Temp. Range -40C to +125C -40C to +125C -40C to +125C Package 10-pin MSOP 10-pin MSOP 10-pin MLFTM Lead Finish Standard Lead-Free Standard
Pin Configuration
SW 1 VIN 2 SYNC_IN 3 SYNC_OUT 4 EN 5 10 GND 9 GND 8 GND 7 BIAS 6 FB
SW VIN SYNC_IN SYNC_OUT
1 2 3 4 5 EN
10 GND 9 GND 8 GND 7 BIAS 6 FB
MSOP-10 (MM)
MLF-10 (ML)
Pin Description
Pin Number 1 2 3 Pin Name SW VIN SYNC_IN Pin Function Switch (Output): Internal power MOSFET output switches. Supply Voltage (Input): Requires bypass capacitor to GND. SYNC_IN for the MIC2204: Sync the main switching frequency to an external clock. Tie pin to ground if not using this function. Tying SYNC_IN high reduces the switching frequency to 1.6MHz (See "Applications Information" section). SYNC_OUT an open collector output to feed into SYNC_IN. Float or ground the SYNC_OUT pin if not using sync out function. A low level EN will power down the device, reducing the quiescent current to under 15A (typ. 6.5A). Input to the error amplifier, connect to the external resistor divider network to set the output voltage. Internal circuit bias supply, nominally 2.3V. Must be de-coupled to signal ground with a 0.01F capacitor. Ground.
4 5 6 7 8, 9, 10
SYNC_OUT EN FB BIAS GND
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Absolute Maximum Ratings(1)
Supply Voltage (VIN) ....................................................... 6V Output Switch Voltage (VSW) .......................................... 6V Logic Input Voltage (VEN, VSYNC_IN) ............... VIN to -0.3V Power Dissipation(2) Storage Temperature (TS) ....................... -65C to +150C
Operating Ratings(3)
Supply Voltage (VIN) ................................... +2.3V to +5.5V Junction Temperature (TJ) ................ -40C TJ +125C Package Thermal Resistance MSOP (JA) ....................................................... 115C/W 3mmx3mm MLFTM-10L (JA) ............................... 60C/W
Electrical Characteristics(4)
TA = 25C with VIN =VEN = 3.5V, unless otherwise noted. Bold values indicate -40C < TJ < +125C Parameter Supply Voltage Range Current Limit Quiescent Current VFB = 0.7V VFB = 1.1V EN = 0V Feedback Voltage Output Voltage Line Regulation Output Voltage Load Regulation Maximum Duty Cycle Switch On-Resistance VOUT = 1V, VIN = 2.3V to 5.5V, ILOAD= 100mA 0mA < ILOAD < 500mA VFB = 0.7V ISW = 300mA, VFB = 0.7V ISW = -300mA, VFB = 1.1V Oscillator Frequency Sync Frequency Range SYNC_IN Threshold Sync Minimum Pulse Width SYNC_IN Input Current Enable Threshold Enable Hysteresis Enable Input Current Overtemperature Shutdown Overtemperature Shutdown Hysteresis
Notes: 1. 2. 3. 4. Exceeding the ABSOLUTE MAXIMUM RATINGS may damage device. Absolute maximum power dissipation is limited by maximum junction temperature where PD(MAX) = (TJ(MAX)-TA) / JA. The device is not guaranteed to function outside its operating rating. Specification for packaged product only.
Condition
Min 2.3 0.6
Typ
Max 5.5
Units V A A A V % % %
1.2 320 6.0
2 450 15 1.02
0.98
1.0 0.2 0.2
100 0.72 0.55 1.8 1.8 1.2 10 1 0.52 0.72 20 1 160 20 2 2 0.96 2 2.2 2.5
MHz MHz V ns A V mV A C C
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Typical Characteristics
Efficiency vs. Output Current
4VIN
100 95 EFFICIENCY (%) 90 85 80 75 70 65 60 55
100 95 90
EFFICIENCY (%)
Efficiency vs. Output Current
4.2VIN
EFFICIENCY (%)
100 95 90 85 80 75 70 65 60 55 50 0
Efficiency vs. Output Current
85 80 75 70 65 60 55 50 0
4.2VIN 3.6VIN 5VIN
3.3VIN
3.5VIN 3VIN
3.6VIN
1.8VOUT 50 100 150 200 250 300 350 400 450 500
2.5VOUT 100 200 300 400 500 OUTPUT CURRENT (mA)
3.3VOUT 100 200 300 400 500 OUTPUT CURRENT (mA)
0
50
OUTPUT CURRENT (mA)
1.01
OUTPUT VOLTAGE (V)
Output Voltage vs. Output Current
1.01
Output Voltage vs. Temperature
VBIAS
2.5 2.0
VBIAS (V)
vs. Supply Voltage
1.005 1.0025 1 0.9975 0.995 0.9925 0.99 0 0.1 0.2 0.3 0.4 OUTPUT CURRENT (A) 0.5
OUTPUT VOLTAGE (V)
1.0075
1.005
1.5 1.0 0.5 VFB = 0V 0 0
1
0.995
0.99 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (C)
2 4 SUPPLY VOLTAGE (V)
6
2.32 2.318
BIAS SUPPLY (V)
Bias Supply vs. Temperature
350 300 250
Quiescent Current vs. Supply Voltage
Quiescent Current vs. Temperature
318 316 314 312 310 308 306 304 302
2.316 2.314 2.312 2.31 2.308 2.306 2.304 2.302 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (C)
150 100 50 0 0 VFB = 0V 1 2 3 4 5 6 SUPPLY VOLTAGE (V)
IQ (A)
IQ (A)
200
300 VIN = 3.6V 298 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (C)
2.40 2.30
Frequency vs. Temperature
ENABLE THRESHOLD (V)
FREQUENCY (MHz)
2.20 2.10 2.00 1.90 1.80 1.70 1.60 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (C)
0.8 0.7 0.6 0.5 0.4 0.3 0.2
Enable On
ENABLE THRESHOLD (V)
1 0.9
Enable Threshold vs. Supply Voltage
0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1
Enable Threshold vs. Temperature
Enable Off
0.1 0 2.3 2.8 3.3 3.8 4.3 4.8 5.3 SUPPLY VOLTAGE (V)
VIN = 3.6V 0 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (C)
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Functional Characteristics
Enable Transient
ENABLE 2V/div
Disable Transient
ENABLE 2V/div
VOUT 500mV/div
VOUT 500mV/div
VIN = 3.6V VOUT = 1V L = 4.7H C = 10F TIME (40s/div.)
VIN = 3.6V VOUT = 1V L = 4.7H C = 10F IOUT = 500mA TIME (40s/div.)
Line Transient
Load Transient
VIN 2V/div
VIN 200mA/div
VOUT 20mV/div
VOUT = 1V L = 4.7H C = 10F IOUT = 500mA TIME (200s/div.)
VOUT 50mV/div
VIN = 3.6V VOUT = 2V L = 4.7H C = 4.7F
TIME (20s/div.)
Switch Node Output Ripple
OUTPUT RIPPLE 10mV/div
VSW 2V/div
VIN = 3.6V VOUT = 1V
IOUT = 500mA L = 4.7H
C = 10F X5R
TIME (400ns/div.)
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Block Diagram
VIN
CIN SYNC_OUT
VIN
SYNC_IN
Oscillator Ramp Generator
BIAS
Internal Supply
Error Amplifier
PWM Comparator SW Driver VOUT
COUT 1.0V
EN MIC2204 FB PGND
MIC2204 Block Diagram
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SYNC_OUT Since SYNC_OUT is an open collector output that provides a signal equal to the internal oscillator frequency, multiple MIC2204s to be connected together in a master-slave configuration for frequency matching of the converters. A typical 10k is recommended for a pull-up resistor. BIAS The bias supply is an internal 2.3V linear regulator that supplies the internal biasing voltage to the MIC2204. A 10nF ceramic capacitor is required on this pin for bypassing. Do not use the BIAS pin as a supply. The BIAS pin was designed to supply internal power and not external circuitry. Feedback The feedback pin provides the control path to control the output. A resistor divider connecting the feedback to the output is used to adjust the desired output voltage. Refer to the "Feedback" material in the "Applications Information" section for more detail.
Functional Description
VIN VIN provides power to the output and to the internal bias supply. The supply voltage range is from 2.3V to 5.5V. A minimum 1F ceramic is recommended for bypassing the input supply. Enable The enable pin provides a logic level control of the output. In the off state, supply current of the device is greatly reduced (typically 6.5A). 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. SYNC_IN SYNC_IN enables the ability to change the fundamental switching frequency. The SYNC_IN frequency has a minimum frequency of 1.8MHz and a maximum sync frequency of 2.5MHz. Careful attention should be paid to not driving the SYNC_IN pin greater than the supply voltage. While this will not damage the device, it will cause improper operation.
MIC2204 Master VIN 10k SYNC_IN SYNC_OUT FB MIC2204 Slave VIN SW BIAS SYNC_IN SYNC_OUT FB SW BIAS
Figure 1. SYNC_OUT
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The size requirements refer to the area and height requirements that are necessary to fit a particular design. Please refer to the inductor dimensions on their data sheet. DC resistance is also important. While DCR is inversely proportional to size, DCR can represent a significant efficiency loss. Refer to the "Efficiency Considerations " below for a more detailed description. Table 1 below shows a list of recommended 4.7H inductors by manufacturer, part number and key specifications. Bias Capacitor A small 10nF ceramic capacitor is required to bypass the BIAS pin. The use of low ESR ceramics provides improved filtering for the bias supply. Efficiency Considerations Efficiency is defined as the amount of useful output power, divided by the amount of power consumed.
Applications Information
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 are not recommended: they lose most of their capacitance over temperature and also become resistive at high frequencies. This reduces their ability to filter out high frequency noise. Output Capacitor The MIC2204 was designed specifically for the use of a 4.7F ceramic output capacitor. The output capacitor requires either an X7R or X5R dielectric. Y5V and Z5U dielectric capacitors, aside from the undesirable effect of their wide variation in capacitance over temperature, become resistive at high frequencies. Using Y5V or Z5U capacitors will cause instability in the MIC2204. For output voltages less than 1.6V, a 10F capacitor may be required for stability. See the "Compensation" section for more detail. Total output capacitance should not exceed 15F. Large values of capacitance can cause current limit to engage during start-up. If larger than 15F is required, a feed-forward capacitor from the output to the feedback node should be used to slow the start-up time. Inductor Selection Inductor selection will be determined by the following (not necessarily in the order of importance): * Inductance * Rated current value * Size requirements * DC resistance (DCR) The MIC2204 is designed for use with a 4.7H inductor. 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% 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.
V xI Efficiency % = OUT OUT x 100 VIN x IIN
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, critical in handheld devices. There are two loss terms in switching converters: DC losses and switching losses. DC losses are simply the power dissipation of I2R. For example, power is dissipated in the highside switch during the on cycle, where 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 to drive the gates on and off at a constant 2MHz frequency and the switching transitions make up the switching losses.
Manufacturer Sumida Murata Murata Coilcraft Low Profile TDK Sumida
P/N CDRH2D18-4R7 LQH43CN4R7M01 LQH32CN4R7M11 1008PS-472M
H(mm) 2 2.6 2.2 2.74
W(mm) 3.2 3.2 2.7 3.8
L(mm) 3.2 4.6 3.4 3.8
DCR(m) 81 150 195 350
LDR5610T-4R7MR90 CMD4D06
1 0.8
5.2 6.3
5.8 5.8
240 216
Table 1. Component Selection Table
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Figure 2 shows an efficiency curve. On the non-shaded portion, from 0 to 200mA, efficiency losses are dominated by quiescent current losses, gate drive and transition losses. In this case, lower supply voltages yield greater efficiency in that they require less current to drive the MOSFETs and have reduced input power consumption.
100 95
EFFICIENCY (%)
Micrel
ing output voltage regulation. With a typical gain bandwidth of 200kHz, the MIC2204 is capable of extremely fast transient responses. The MIC2204 is designed to be stable with a 4.7H inductor and a 4.7F ceramic (X5R) output capacitor for output voltages greater than 1.6V. For output voltages less than 1.6V, a 10F capacitor is required. Also, when a feed forward capacitor is used, the gain bandwidth is increased to unity gain. This will also require increasing the output capacitor to 10F. Feedback The MIC2204 provides a feedback pin to adjust the output voltage to the desired level. This pin connects internally to an error amplifier. The error amplifier then compares the voltage at the feedback to the internal 1V reference voltage and adjusts the output voltage to maintain regulation. To calculate the resistor divider network for the desired output is as follows:
R2 = R1 VOUT - 1 V REF
Efficiency vs. Output Current
90 85 80 75 70 65 60 55 50 0
4.2VIN 5VIN
3.6VIN
3.3VOUT 100 200 300 400 500 OUTPUT CURRENT (A)
Figure 2. On the shaded region, 200mA to 500mA, 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, reducing the internal RDSON. This improves efficiency by reducing DC losses in the device. All but the inductor losses are inherent to the device, making inductor selection even more 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: LPD=IOUT2 x DCR From that, the loss in efficiency due to inductor resistance can be calculated as follows:
Where VREF is 1.0V and VOUT is the desired output voltage. A 10k or lower resistor value from the output to the feedback is recommended. Larger resistor values require an additional capacitor (feed-forward) from the output to the feedback. The large high-side resistor value and the parasitic capacitance on the feedback pin (~10pF) can cause an additional pole in the loop. The additional pole can create a phase loss at high-frequency. This phase loss degrades transient response by reducing phase margin. Adding feed-forward capacitance negates the parasitic capacitive effects of the feedback pin. A minimum 1000pF capacitor is recommended for feedforward capacitance. Also, large feedback resistor values increase the impedance, making the feedback node more susceptible to noise pick-up. A feed-forward capacitor would also reduce noise pick-up by providing a low impedance path to the output. When using a feed-forward capacitor, the gain bandwidth of the device reaches unity gain at high-frequency. Therefore, output capacitance will need to be increased to a minimum 10F. For more information on output capacitor selection for stability, see the "Compensation " section.
VOUT x IOUT Efficiency Loss = 1- x 100 VOUT x IOUT + LPD
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. Compensation The MIC2204 is an internally compensated, voltage-mode buck regulator. Voltage mode is achieved by creating an internal 2MHz ramp signal and using the output of the error amplifier to pulsewidth modulate the switch node, maintain-
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PWM Operation The MIC2204 is a pulsewidth modulation (PWM) controller. By controlling the ratio of on-to-off time, or duty cycle, a regulated DC output voltage is achieved. As load or supply voltage changes, so does the duty cycle to maintain a constant output voltage. In cases where the input supply runs into a dropout condition, the MIC2204 will run at 100% duty cycle. The MIC2204 provides constant switching at 2MHz with synchronous internal MOSFETs. The internal MOSFETs include a high-side P-Channel MOSFET from the input supply to the switch pin and an N-Channel MOSFET from the switch pin to ground. Since the low-side N-Channel MOSFET provides the current during the off cycle, a free wheeling Schottky diode from the switch node to ground is not required. PWM control provides fixed frequency operation. By maintaining a constant switching frequency, predictable fundamental and harmonic frequencies are achieved. Other methods of regulation, such as burst and skip modes, have frequency spectrums that change with load and can interfere with sensitive communication equipment. Synchronization
Micrel
SYNC_IN allows the user to change the frequency from 2MHz up to 2.5MHz or down to 1.8MHz. This controls the fundamental frequency and all the resultant harmonics. Maintaining a predictable frequency creates the ability to either shift the harmonics away from sensitive carrier and IF frequency bands, or to accurately filter out specific harmonic frequencies. Connecting the SYNC_OUT function pin to the SYNC_IN of other MIC2204s will synchronize multiple MIC2204s in a daisy-chain. Synchronizing multiple MIC2204s means that regulators will run at the same fundamental frequency, resulting in matched harmonic frequencies and simplifying design for sensitive communication equipment.
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Package Information
3.15 (0.122) 2.85 (0.114)
4.90 BSC (0.193)
DIMENSIONS: MM (INCH)
3.10 (0.122) 2.90 (0.114) 1.10 (0.043) 0.94 (0.037)
0.26 (0.010) 0.10 (0.004)
0.30 (0.012) 0.15 (0.006) 0.50 BSC (0.020)
0.15 (0.006) 0.05 (0.002)
6 MAX 0 MIN
0.70 (0.028) 0.40 (0.016)
10-Pin MSOP (MM)
DIMENSIONS: mm
0.85 +0.15 -0.05 3.00 BSC. 1.50 BSC. 0.48 typ. 0.01 +0.04 -0.01 0.23 +0.07 -0.05 1 2 3 0.20 dia 3.00 BSC. 1 2 3 1.15 +0.15 -0.15 2.30 +0.15 -0.15 1.60 +0.15 -0.15 0.80 +0.15 -0.15 PIN 1 ID
1.50 BSC.
0.50 BSC. 0.40 +0.15 -0.05 TOP BOTTOM
SEATING PLANE TERMINAL TIP
0.23 +0.07 -0.05
0.01 +0.04 -0.01
0.50 BSC. TERMINAL TIP ODD TERMINAL SIDE
0.50 BSC.
EVEN TERMINAL SIDE
10-Pin MLFTM (ML)
MICREL, INC. 1849 FORTUNE DRIVE SAN JOSE, CA 95131
TEL
USA
+ 1 (408) 944-0800
FAX
+ 1 (408) 944-0970
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 at Purchaser's own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale. (c) 2004 Micrel, Incorporated.
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