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MIC2290
2mm x 2mm PWM Boost Regulator with Internal Schotty Diode
General Description
The MIC2290 is a 1.2MHz, PWM, boost-switching regulator housed in the small size 2mm x 2mm 8-pin MLF(R) package. The MIC2290 features an internal Schottky diode that reduces circuit board area and total solution cost. High power density is achieved with the MIC2290's internal 34V/0.5A switch, allowing it to power large loads in a tiny footprint. The MIC2290 implements a constant frequency 1.2MHz PWM control scheme. The high frequency operation saves board space by reducing external component sizes. The fixed frequency PWM topology also reduces switching noise and ripple to the input power source. The MIC2290's wide 2.5V to 10V input voltage allows direct operation from 3- to 4-cell NiCad/NiMH/Alkaline batteries, 1-and 2-cell Li-Ion batteries, as well as fixed 3.3V and 5V systems. The MIC2290 is available in a low-profile 2mmx2mm 8-pin MLF(R) leadless package and operates from a junction temperature range of -40C to +125C. Data sheets and support documentation can be found on Micrel's web site at: www.micrel.com.
Features
* * * * * * * * * * * * * * Internal Schottky diode 2.5V to 10V input voltage Output voltage adjustable to 34V Over 500mA switch current 1.2MHz PWM operation Stable with ceramic capacitors <1% line and load regulation Low input and output ripple <1A shutdown current UVLO Output overvoltage protection Over temperature protection 2mm x 2mm 8-pin MLF(R) package -40C to +125C junction temperature range
Applications
* * * * * Organic EL power supply TFT LCD bias supply 12V DSL power supply CCD bias supply SEPIC converters
___________________________________________________________________________________________________________
Typical Application
VIN L1 10H VOUT 12V
12VOUT Efficiency
85 80 VIN = 4.2V
2 3
VIN EN
SW OUT
7
EFFICIENCY (%)
MIC2290 R1
1 6
75 70 65 60
VIN = 3.2V VIN = 3.6V
Li Ion Battery
C1 1F
GND
FB
C2 10F R2
4, 8
0
0.02 0.04 0.06 0.08 LOAD CURRENT (A)
0.1
Simple 12V Boost Regulator
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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MIC2290
Ordering Information
Part Number MIC2290BML MIC2290YML Marking Code SRC SRC Output Voltage Adj. Adj. Overvoltage Protection 34V 34V Junction Temp. Range -40 to +125C -40 to +125C Package 8-Pin 2x2 MLF(R) 8-Pin 2x2 MLF
(R)
Lead Finish Standard Pb-Free
Pin Configuration
OUT VIN EN AGND
1 2 3 4 8 7 6 5
PGND SW FB NC
8-Pin 2mm x 2mm MLF(R) (ML) (Top View)
Pin Description
Pin Number 1 Pin Name OUT Pin Function Output pin (Output): Output voltage. Connect to FB resistor divider. This pin has an internal 34V output overvoltage clamp. See "Block Diagram" and "Applications" section for more information. Supply (Input): 2.5V to 10V input voltage. Enable (Input): Logic high enables regulator. Logic low shuts down regulator. Analog ground. No connect (no internal connection to die). Feedback (Input): Output voltage sense node. Connect feedback resistor network to this pin. VOUT = 1.24V 1 +
2 3 4 5 6
VIN EN AGND NC FB

R1 . R2
7 8 EP
SW PGND GND
Switch node (Input): Internal power Bipolar collector. Power ground. Ground (Return): Exposed backside pad.
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Absolute Maximum Ratings(1)
Supply Voltage (VIN) .......................................................12V Switch Voltage (VSW)....................................... -0.3V to 34V Enable Pin Voltage (VEN)................................... -0.3V to VIN FB Voltage (VFB)...............................................................6V Switch Current (ISW) .........................................................2A Storage Temperature (Ts) .........................-65C to +150C ESD Rating(3) .................................................................. 2kV
Operating Ratings(2)
Supply Voltage (VIN).......................................... 2.5V to 10V Ambient Temperature (TJ)......................... -40C to +125C Package Thermal Resistance 2x2 MLF-8 (JA) .................................................93C/W
Electrical Characteristics(4)
TA = 25C, VIN = VEN = 3.6V, VOUT = 15V, IOUT = 40mA, unless otherwise noted. Bold values indicate -40C TJ 125C.
Symbol VIN VUVLO IVIN ISD VFB IFB Parameter Supply Voltage Range Undervoltage Lockout Quiescent Current Shutdown Current Feedback Voltage Feedback Input Current Line Regulation Load Regulation DMAX ISW VSW ISW VEN IEN fSW VD IRD VOVP TJ
Notes: 1. Absolute maximum ratings indicate limits beyond which damage to the component may occur. Electrical specifications do not apply when operating the device outside of its operating ratings. The maximum allowable power dissipation is a function of the maximum junction temperature, TJ(max), the junction-to-ambient thermal resistance, JA, and the ambient temperature, TA. The maximum allowable power dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown. 2. The device is not guaranteed to function outside its operating rating. 3. IC devices are inherently ESD sensitive. Handling precautions required. Human body model rating: 1.5K in series with 100pF. 4. Specification for packaged product only. 5. ISD = IVIN.
Condition
Min 2.5 1.8
Typ 2.1 2.5 0.2
Max 10 2.4 5 1 1.252 1.265 1
Units V V mA A V V nA % % % A mV
VFB = 2V, (not switching) VEN = 0V, Note 5 (1%) (2%) (Over Temp) VFB = 1.24V 3V VIN 5V 5mA IOUT 20mA 85 ISW = 0.5A VEN = 0V, VSW = 10V Turn on Turn off VEN = 10V 1.05 ID = 150mA VR = 30V (nominal voltage) Hysteresis 30 1.5 1.227 1.215
1.24 -450 0.1 0.2 90 0.75 450 0.01
Maximum Duty Cycle Switch Current Limit Switch Saturation Voltage Switch Leakage Current Enable Threshold Enable Pin Current Oscillator Frequency Schottky Forward Drop Schottky Leakage Current Overvoltage Protection Overtemperature Threshold Shutdown
5 0.4
A V V A MHz V A V C C
20 1.2 0.8 32 150 10
40 1.35 1 4 34
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Typical Characteristics
Efficiency at V = 12V OUT
VIN = 4.2V
90 85 EFFICIENCY (%) 80 75
70 VIN = 3.6V 65 60 55 50 0 25 50 75 100 OUTPUT CURRENT (mA) VIN = 3.3V
0.9 0.8 CURRENT LIMIT (A) 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 2.5
Current Limit vs. Supply Voltage
4 5.5 7 8.5 SUPPLY VOLTAGE (V)
10
SWITCH SATURATION VOLTAGE (mV)
700 600
Switch Saturation Voltage vs. Temperature
1.40 1.35 FREQUENCY (MHz) 1.30 1.25 1.20 1.15 1.10 1.05
Frequency vs. Temperature
500 400 300 200 100 VIN = 3.6V ISW = 500mA
0 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (C)
1.00 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (C)
99 MAXIMUM DUTY CYCLE (%) 97 95 93 91 89 87
Maximum Duty Cycle vs. Temperature
FEEDBACK CURRENT (nA)
700 600 500 400 300 200 100
FB Pin Current vs. Temperature
VIN = 3.6V
85 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (C)
0 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (C)
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Typical Characteristics (continued)
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Functional Characteristics
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Functional Diagram
VIN FB EN OUT
OVP SW gm VREF 1.24V S CA PWM Generator
1.2MHz Oscillator
Ramp Generator
GND
Figure 1. MIC2290 Block Diagram
Functional Description
The MIC2290 is a constant frequency, PWM current mode boost regulator. The block diagram is shown in Figure 1. The MIC2290 is composed of an oscillator, slope compensation ramp generator, current amplifier, gm error amplifier, PWM generator, and a 0.5A bipolar output transistor. The oscillator generates a 1.2MHz clock. The clock's two functions are to trigger the PWM generator that turns on the output transistor, and to reset the slope compensation ramp generator. The current amplifier is used to measure the switch current by amplifying the voltage signal from the internal sense resistor. The output of the current amplifier is summed with the output of the slope compensation ramp generator. This summed current-loop signal is fed to one of the inputs of the PWM generator.
The gm error amplifier measures the feedback voltage through the external feedback resistors and amplifies the error between the detected signal and the 1.24V reference voltage. The output of the gm error amplifier provides the voltage-loop signal that is fed to the other input of the PWM generator. When the current-loop signal exceeds the voltage-loop signal, the PWM generator turns off the bipolar output transistor. The next clock period initiates the next switching cycle, maintaining the constant frequency current-mode PWM control.
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when an overvoltage condition is detected, saving itself and other sensitive circuitry downstream.
Application Information
DC-to-DC PWM Boost Conversion The MIC2290 is a constant frequency boost converter. It operates by taking a DC input voltage and regulating a higher DC output voltage. Figure 2 shows a typical circuit. Boost regulation is achieved by turning on an internal switch, which draws current through the inductor (L1). When the switch turns off, the inductor's magnetic field collapses, causing the current to be discharged into the output capacitor through an internal Schottky diode (D1). Voltage regulation is achieved through pulse-width modulation (PWM).
V IN L1 10H VOUT
Component Selection
Inductor Inductor selection is a balance between efficiency, stability, cost, size, and rated current. For most applications, a 10H is the recommended inductor value; it is usually a good balance between these considerations. Large inductance values reduce the peak-to-peak ripple current, affecting efficiency. This has an effect of reducing both the DC losses and the transition losses. There is also a secondary effect of an inductor's DC resistance (DCR). The DCR of an inductor will be higher for more inductance in the same package size. This is due to the longer windings required for an increase in inductance. Since the majority of input current (minus the MIC2290 operating current) is passed through the inductor, higher DCR inductors will reduce efficiency. To maintain stability, increasing inductor size will have to be met with an increase in output capacitance. This is due to the unavoidable "right half plane zero" effect for the continuous current boost converter topology. The frequency at which the right half plane zero occurs can be calculated as follows:
Frhpz = VOUT VIN x L x IOUT x 2
2
MIC2290 VIN C1 2.2F EN GND GND SW OUT FB R2 GND R1 C2 10F
Figure 2. Typical Application Circuit
Duty Cycle Considerations Duty cycle refers to the switch on-to-off time ratio and can be calculated as follows for a boost regulator:
D = 1- VIN VOUT
The duty cycle required for voltage conversion should be less than the maximum duty cycle of 85%. Also, in light load conditions where the input voltage is close to the output voltage, the minimum duty cycle can cause pulse skipping. This is due to the energy stored in the inductor causing the output to overshoot slightly over the regulated output voltage. During the next cycle, the error amplifier detects the output as being high and skips the following pulse. This effect can be reduced by increasing the minimum load or by increasing the inductor value. Increasing the inductor value reduces peak current, which in turn reduces energy transfer in each cycle.
The right half plane zero has the undesirable effect of increasing gain, while decreasing phase. This requires that the loop gain is rolled off before this has significant effect on the total loop response. This can be accomplished by either reducing inductance (increasing RHPZ frequency) or increasing the output capacitor value (decreasing loop gain).
Overvoltage Protection For the MLF(R) package option, there is an overvoltage protection function. If the feedback resistors are disconnected from the circuit or the feedback pin is shorted to ground, the feedback pin will fall to ground potential. This will cause the MIC2290 to switch at full duty cycle in an attempt to maintain the feedback voltage. As a result, the output voltage will climb out of control. This may cause the switch node voltage to exceed its maximum voltage rating, possibly damaging the IC and the external components. To ensure the highest level of protection, the MIC2290 OVP pin will shut the switch off
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Output Capacitor Output capacitor selection is also a trade-off between performance, size, and cost. Increasing output capacitance will lead to an improved transient response, but also an increase in size and cost. X5R or X7R dielectric ceramic capacitors are recommended for designs with the MIC2290. Y5V values may be used, but to offset their tolerance over temperature, more capacitance is required. The following table shows the recommended ceramic (X5R) output capacitor value vs. output voltage.
Output Voltage <6V <16V <34V Recommended Output Capacitance 22F 10F 4.7F
Table 1. Output Capacitor Selection M9999-101907
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MIC2290
Input capacitor A minimum 1F ceramic capacitor is recommended for designing with the MIC2290. Increasing input capacitance will improve performance and greater noise immunity on the source. The input capacitor should be as close as possible to the inductor and the MIC2290, with short traces for good noise performance.
Feedback Resistors The MIC2290 utilizes a feedback pin to compare the output to an internal reference. The output voltage is adjusted by selecting the appropriate feedback resistor network values. The R2 resistor value must be less than or equal to 5k (R2 5k). The desired output voltage can be calculated as follows:
R1 VOUT = VREF x + 1 R2
where VREF is equal to 1.24V.
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Application Circuits
V IN 3.3V L1 4.7H VOUT 5V @ 180mA
VIN 3V to 4.2V L1 10H VOUT 15V @ 45mA
MIC2290 C1 2.2F 6.3V VIN SW OUT EN GND GND
C1 C2 L1 2.2F, 6.3V, 0805 X5R Ceramic Capacitor 10F, 6.3V, 0805 X5R Ceramic Capacitor 4.7H, 450mA Inductor
MIC2290
R1 15k
FB R2 5k
C2 10F 6.3V
C1 2.2F 6.3V
VIN
SW OUT
R1 54.9k
EN GND
FB R2 5k
C2 10F 16V
GND
AVX AVX Murata C1 C2 L1
GND
2.2F, 6.3V, 0603 X5R Ceramic Capacitor 10F, 16V, 1206 X5R Ceramic Capacitor 10H, 450mA Inductor
GND
AVX AVX Murata
08056D475MAT 08056D106MAT LQH32CN4R7N11
06036D225MAT 1206YD106MAT LQH32CN100K11
Figure 3. 3.3VIN to 5VOUT @ 180mA
Figure 6. 3.3VIN to 4.2VOUT to 15VOUT @ 45mA
VIN 3V to 4.2V
L1 10H
VOUT 9V @ 80mA
V IN 5V
L1 10H
VOUT 9V @ 160mA
MIC2290 C1 2.2F 6.3V VIN SW OUT EN GND GND
C1 C2 L1 2.2F, 6.3V, 0603 X5R Ceramic Capacitor 10F, 16V, 1206 X5R Ceramic Capacitor 10H, 450mA Inductor
MIC2290
R1 31.6k C2 10F 16V
FB R2 5k
C1 2.2F 6.3V
VIN
SW OUT
R1 31.6k
EN GND
FB R2 5k
C2 10F 16V
GND
AVX AVX Murata C1 C2 L1
GND
2.2F, 6.3V, 0603 X5R Ceramic Capacitor 10F, 16V, 1206 X5R Ceramic Capacitor 10H, 450mA Inductor
GND
AVX AVX Murata
06036D225MAT 1206YD106MAT LQH32CN100K11
06036D225MAT 1206YD106MAT LQH32CN100K11
Figure 4. 3.3VIN to 4.2VOUT to 9VOUT @ 80mA
Figure 7. 5VIN to 9VOUT @ 160mA
VIN 3V to 4.2V
L1 10H
VOUT 12V @ 50mA
V IN 5V
L1 10H
VOUT 12V @ 110mA
MIC2290 C1 2.2F 6.3V VIN SW OUT EN GND GND
C1 C2 L1 2.2F, 6.3V, 0603 X5R Ceramic Capacitor 10F, 16V, 1206 X5R Ceramic Capacitor 10H, 450mA Inductor
MIC2290
R1 43.2k C2 10F 16V
FB R2 5k
C1 2.2F 6.3V
VIN
SW OUT
R1 43.2k
EN GND
FB R2 5k
C2 10F 16V
GND
AVX AVX Murata C1 C2 L1
GND
2.2F, 6.3V, 0603 X5R Ceramic Capacitor 10F, 16V, 1206 X5R Ceramic Capacitor 10H, 450mA Inductor
GND
AVX AVX Murata
06036D225MAT 1206YD106MAT LQH32CN100K11
06036D225MAT 1206YD106MAT LQH32CN100K11
Figure 5. 3.3VIN to 4.2VOUT to 12VOUT @ 50mA
Figure 8. 5VIN to 12VOUT @ 110mA
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V IN 5V
L1 10H
VOUT 24V @ 40mA
MIC2290 C1 2.2F 6.3V VIN SW OUT EN GND GND
C1 C2 L1 2.2F, 6.3V, 0603 X5R Ceramic Capacitor 4.7F, 25V, 1206 X5R Ceramic Capacitor 10H, 450mA Inductor
R1 18.2k
FB R2 1k
C2 4.7F 25V
GND
AVX AVX Murata
06036D225MAT 12063D475MAT LQH32CN100K11
Figure 9. 5VIN to 24VOUT @ 40mA
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Package Information
8-Pin 2mm x 2mm MLF(R) (ML)
Grey Shaded area indica tes Thermal Via. Size should be 0 .300mm in diameter and it should be connected to GND for maximum thermal performance
Recommended Land Pattern for (2mm x 2mm) 8-Pin MLF(R)
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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) 2004 Micrel, Incorporated.
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