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MIC2295
High Power Density 1.2A Boost Regulator
General Description
The MIC2295 is a 1.2Mhz, PWM dc/dc boost switching regulator available in low profile Thin SOT23 and 2mm x 2mm MLF package options. High power density is achieved with the MIC2295's internal 34V / 1.2A switch, allowing it to power large loads in a tiny footprint. The MIC2295 implements constant frequency 1.2MHz PWM current mode control. The MIC2295 offers internal compensation that offers excellent transient response and output regulation performance. The high frequency operation saves board space by allowing small, low-profile external components. The fixed frequency PWM scheme also reduces spurious switching noise and ripple to the input power source. The MIC2295 is available in a low-profile Thin SOT23 5-lead package and a 2mm x2mm 8-lead MLF leadless package. The 2mm x 2mm MLF package option has an output over-voltage protection feature. The MIC2295 has an operating junction temperature range of -40C to +125C
Features
* * * * * * * * * * * * * 2.5V to 10V input voltage range Output voltage adjustable to 34V 1.2A switch current 1.2MHz PWM operation Stable with small size ceramic capacitors High efficiency Low input and output ripple <1mA shutdown current UVLO Output over-voltage protection (MIC2295BML) Over temperature shutdown Thin SOT23-5 package option 2mm x 2mm leadless 8-lead MLF package option -40oC to +125oC junction temperature range
*
Applications
* Organic EL power supplies * 3.3V to 5V/500mA conversion * TFT-LCD bias supplies * Flash LED drivers * Positive and negative output regulators * SEPIC converters * Positive to negative Cuk converters * 12V supply for DSL applications Multi-output dc/dc converters
10H
VOUT 15V/100mA
L1 10H
VOUT 5V/500mA
VIN 1-Cell Li Ion 3V to 4.2V
MIC2295BML SW OVP FB EN VIN C1 2.2F AGND PGND R2 9.01K
MIC2295 BD5
R1 100k 2.2F
VIN VIN 1-Cell Li Ion EN C1 2.2F
SW FB
R1 10k 10F R2 3.3k
GND
MLF and MicroLeadFrame is a trademark of Amkor Technology
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Micrel
MIC2295
Ordering Information
Part Number Standard Lead-Free Output Over Voltage Protection Marking Code Standard Lead-Free Thin SOT235 2mm x2mm MLF-8L Junction Temperature Range Package
MIC2295BD5 MIC2295BML
MIC2295YD5 MIC2295YML
34V
SVAA SXA
SVAA SXA
-40C to 125C
-40C to 125C
Pin Configuration
Pin Description
MIC2295BD5 Thin SOT-23-5 1 2 3 4 5 MIC2295BML 2x2 MLF-8L 7 6 3 2 1 Pin Name Pin Function
SW GND FB EN VIN OVP
5 4 8 EP July 2004
N/C AGND PGND GND
Switch Node (Input): Internal power BIPOLAR collector. Ground (Return): Ground. Feedback (Input): 1.24V output voltage sense node. VOUT = 1.24V ( 1 + R1/R2) Enable (Input): Logic high enables regulator. Logic low shuts down regulator. Supply (Input): 2.5V to 10V input voltage. Output Over-Voltage Protection (Input): Tie this pin to VOUT to clamp the output voltage to 34V maximum in fault conditions. Tie this pin to ground if OVP function is not required. No connect. No internal connection to die. Analog ground Power ground Ground (Return). Exposed backside pad. 2 M9999-052402 (408) 955-1690
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MIC2295
Absolute Maximum Rating (1)
Supply voltage (VIN) ............................. 12V Switch voltage (VSW) ........................ -0.3V to 34V Enable pin voltage (VEN) .......................... -0.3 to VIN FB Voltage (VFB)..................................................6V Switch Current (ISW) ....................................... 2.5A Ambient Storage Temperature (TS) .... -65C to +150C ESD Rating(3)................................. ........2KV
Operating Range (2)
Supply Voltage (VIN) ............................. 2.5V to 10V Junction Temperature Range (TJ) ...... -40C to +125C Package Thermal Impedance 93C/W JA 2x2 MLF-8L lead ........................ JA ThinSOT23-5 lead ........................ 256C/W
Electrical Characteristics T =25 C, V
A o
IN
=VEN = 3.6V, VOUT = 15V, IOUT = 40mA, unless otherwise noted. Bold values
indicate -40C
TJ
125C.
Symbol VIN VUVLO IVIN ISD VFB
Parameter Supply Voltage Range Under-Voltage Lockout Quiescent Current Shutdown Current Feedback Voltage
Condition
Min 2.5 1.8
Typ 2.1 2.8 0.1 1.24
VFB = 2V (not switching) VEN = 0V(4) (+/-1%) (+/-2%) (Over Temp) 1.227 1.215
Max 10 2.4 5 1 1.252
Units V V mA mA V
1.265 -450 0.04 1 1.5 nA % % % A mV mA V mA MHz V C C
IFB
Feedback Input Current Line Regulation Load Regulation
VFB = 1.24V 3V 5mA VIN 5V 40mA 85 Note 5 ISW = 1.2A VEN = 0V, VSW = 10V TURN ON TURN OFF VEN = 10V MIC2295BML only Hysteresis 1.2 IOUT
DMAX ISW VSW ISW VEN IEN fSW VOVP Tj
Notes: 1.
Maximum Duty Cycle Switch Current Limit Switch Saturation Voltage Switch Leakage Current Enable Threshold Enable Pin Current Oscillator Frequency Output over-voltage protection Over-Temperature Threshold Shutdown
90 1.7 600 0.01
5 0.4 40 1.35 34
1.5 20 1.2 32 150 10
1.05 30
2. 3. 4. 5.
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. This device is not guaranteed to operate beyond its specified operating rating. IC devices are inherently ESD sensitive. Handling precautions required. Human body model rating: 1.5K in series with 100pF. ISD = IVIN. Guaranteed by design.
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MIC2295
Typical Characteristics
80 75 70 65 Efficiency 60 55 50 45 40 35 30 0 100 200 300 Output Current Vin=4V Vin=5V Vin=5.5V
GND 2 FB
MIC2295 -5V Output
VIN = 5V
5
C3 L1 1uF/16V
1 SW
L2
VOUT = -5V @ 0.15A
C1 1 F/ 6.3V
VIN
CMHSH5-2L
MIC2295BML
4 EN OVP 3
C2 4.7uF/ 6.3V R3 10K
R1 10K
L1 = Murata LQH32CN4R7M23 L2 = Murata LQH32CN4R7M23 C4 1uF/ 6.3V
MIC6211
+ -
R2 2.49K
15V Short circuit protected Boost
85
Sumida CDRH4D18 4.7H
5 VIN 1 SW 0.1uF/ 6.3V
VOUT = 15V / 50mA
80
EFFICIENCY (%)
75
1-Cell Li Ion
Vin=2.5 V Vin=3V
10F/ 6.3V
4
EN
MIC2295
FB GND 2 3
160K
4.7F/ 25V
70
65
10K
60 0 20 40 60 80 100
OUTPUT CURRENT (mA)
CIN = JMK212BJ106MG (Taiyo Yuden )
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MIC2295 SEPIC 5V Output
78 76 74 72 70 68 66 64 0 50 100 150 200 250
VIN = 3.3V to 5.5V
5
L1 4.7uH
C3 1uF/16V
1 SW
MBRX140 4.7uH L2
VOUT = 5V @ 0.3A C4 470pF/ 10V
EFFICIENCY (%)
C1 F/ 6.3V
Vin=3V Vin=3.5V Vin=4V Vin=5V Vin=5.5V
VIN
R1 43.2K
MIC2295BML
4 EN FB GND 2 3
C2 4.7uF/ 6.3V
R2 14.3K L1 = Murata LQH32CN4R7M23 L2 = Murata LQH32CN4R7M23
OUTPUT CURRENT (mA)
5V MIC2295 SEPIC with one coupled inductor
80 75 70 65
VI N = 3 .3 V to 5 V .5
5
C3 L1 1 uF 6 /1 V 4 .7 uH
1 SW
M BRX1 4 0
VOUT = 5 V @0 .3 A R1 43 K .2 C4 470 / pF 10 V
EFICIENCY (%)
60 55 50 45 40 35 30 0 50 100 150 200 250 300
C1 4. 7 F / 6 .3 V
VI N
4 uH .7 L1
M IC2 2 9 5 L BM
4 EN FB 3
C2 4 .7 uF / 6V .3
Vin=2.5 V Vin=3.3 V Vin=5V
GND 2
R2 14 K .3 L 1 = Sum ida CLS 1 5 D1 /HP
LOAD CURRENT (mA)
MIC2295 12V output Efficiency
90 85
Max Duty Cycle vs Input Voltage
100 95 90 85 80 75 70 2.5
0.5 2.5 1.5
Input Voltage vs. Supply Voltage
1.3
DUTY CYCLE
80 75 70
FREQUENCY (MHz)
EFFICIENCY (%)
1.1
0.9
65 60 0 50 100
Vin=3.3V Vin=4.2V Vin=3.6V
150 200
0.7
4
5.5
7
8.5
10
4
5.5
7
8.5
10
OUTPUT CURRENT (mA)
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
Switch Voltage vs. Supply Voltage
300 250
MIC2295 15V output Efficiency
90 85
200 150 100 50 0 2.5
80 75 70 65 60
FEEDBACK VOLTAGE (V)
EFFICIENCY (%)
Switch Voltage (mV)
1.30 1.28 1.26 1.24 1.22
Feedback Voltage vs. Temperature
Vin=3.3V Vin=4V Vin=4.2V
0 50 100 150 200
4.5
6.5
8.5
Input Voltage (V)
OUTPUT CURRENT (mA)
1.20 1.18 1.16 1.14 1.12 1.10 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (C)
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1.4 FREQUENCY (MHz) 1.3 1.2 1.1 1.0 0.9
Frequency vs. Temperature
1.4 1.2 CURRENT LIMIT (A) 1.0 0.8 0.6 0.4 0.2
Current Limit vs. Temperature
OUTPUT VOLTAGE (V)
12.2 12.15 12.1 12.05 12 11.95 11.9 11.85 11.8 0
Load Regulation
V 25
IN
= 3.6V
0.8 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (C)
0 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (C)
50 75 100 125 150 LOAD (mA)
MAXIMUM DUTY CYCLE (%)
FEEDBACK CURRENT (nA)
100 98 96 94 92 90 88 86 84 82 80 2.5
Maximum Duty Cycle vs. Supply Voltage
700 600 500 400 300 200 100
FB Pin Current vs. Temperature
4 5.5 7 8.5 SUPPLY VOLTAGE (V)
10
0 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (C)
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MIC2295
Line Transient Response
OUTPUT VOLTAGE (1mV/div) AC-Coupled
OUTPUT VOLTAGE (50mV/div)
Switching Waveforms
Output Voltage
INDUCTOR CURRENT (500mA/div)
Inductor Current (10H)
INPUT VOLTAGE (2V/div)
4.2V
SWITCH SATURATION (5V/div)
VSW 3.6VIN 12VOUT 150mA
3.2V 12VOUT 150mA Load Time (400s/div)
Time (400ns/div)
Enable Characteristics VIN = 3.6V
LOAD CURRENT OUTPUT VOLTAGE (2V/div.) (5V/div.)
VIN=3.6V
3.6VIN 12VOUT 150mA Load
TIME (400s/div.)
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MIC2295
Functional Description
The MIC2295 is a high power density, PWM dc/dc boost regulator. The block diagram is shown in Figure 1. The MIC2295 is composed of an oscillator, slope compensation ramp generator, current amplifier, gm error amplifier, PWM generator, and a 1.2A 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 voltageloop signal, the PWM generator turns off the bipolar output transistor. The next clock period initiates the next switching cycle, maintaining constant frequency current-mode PWM control
VIN
FB
OVP*
EN
MIC2295
OVP* SW PWM Generator
gm
VREF
1.24V CA
1.2MHz Oscillator *OVP available on MLFTM package option only.
Ramp Generator
GND
MIC2295 Block Diargam
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MIC2295
Application Information
DC to DC PWM Boost Conversion The MIC2295 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.
Vin
L1 10uH D1 1A/40V Schottky Vout
VIN EN
SW OVP
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 MIC2295 OVP pin will shut the switch off when an over-voltage condition is detected saving itself and other sensitive circuitry downstream.
MIC2288BML
FB
R1
C2 10uF
Component Selection
Inductor Inductor selection is a balance between efficiency, stability, cost, size and rated current. For most applications a 10uH is the recommended inductor value. It is usually a good balance between these considerations. Efficiency is affected by inductance value in that larger inductance values reduce the peak to peak ripple current. This has an effect of reducing both the DC losses and the transition losses. There is also a secondary effect of an inductors 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 MIC2295 operating current) is passed through the inductor, higher DCR inductors will reduce efficiency. Also, 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; VIN 2 Frhpz = VOUT L IOUT 2 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). 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 9 M9999-052402 (408) 955-1690
R2
GND
Gnd
Gnd
Figure 2. Typical Application
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 external Schottkey diode (D1). Voltage regulation is achieved my modulating the pulse width or pulse width modulation (PWM). Duty Cycle Considerations Duty cycle refers to the switch on-to-off time ratio and can be calculated as follows for a boost regulator; VIN D =1 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. Over Voltage Protection For MLF package of MIC2295, there is an over voltage 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 MIC2295 to July 2004
Micrel
MIC2295
or X7R dielectric ceramic capacitors are recommended for designs with the MIC2295. 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 Diode Selection The MIC2295 requires an external diode for operation. A Schottkey diode is recommended for most applications due to their lower forward voltage drop and reverse recovery time. Ensure the diode selected can deliver the peak inductor current and the maximum reverse voltage is rated greater than the output voltage. Input Capacitor A minimum 1uF ceramic capacitor is recommended for designing with the MIC2295. 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 MIC2295, with short traces for good noise performance. Feedback Resistors The MIC2295 utilizes a feedback pin to compare the output to an internal reference. The output voltage is adjusted by selecting the appropriate feedback resistor values. The desired output voltage can be calculated as follows; R1 VOUT = VREF +1 R2 Recommended Output Capacitance 10F 4.7F 2.2F
Output Voltage Setting The following equation can be used to select the feedback resistors R1 and R2 (see figure 1). VOUT R1 = R 2 1 1.24V A high value of R2 can increase the whole system efficiency, but the feedback pin input current (IFB) of the gm operation amplifier will affect the output voltage. An R2 value of xx KW is suitable for most applications Inductor Selection In MIC2295, the switch current limit is 1.2A. The selected inductor should handle at least 1.2A current without saturating. The inductor should have a low DC resistor to minimize power losses. The inductor's value can be 4.7uH to 10uH for most applications. Capacitor Selection Multi-layer ceramic capacitors are the best choice for input and output capacitors. They offer extremely low ESR, allowing very low ripple, and are available in very small, cost effective packages. X5R dielectrics are preferred. A 4.7uF to 10uF output capacitor is suitable for most applications. Diode Selection For maximum efficiency, Schottky diode is recommended for use with MIC2295. An optimal component selection can be made by choosing the appropriate reverse blocking voltage rating and the average forward current rating for a given application. For the case of maximum output voltage (34V) and maximum output current capability, a 40V / 1A Schottky diode should be used. Open-Circuit Protection For MLF package option of MIC2295, there is an output over-voltage protection function that clamps the output to below 34V in fault conditions. Possible fault conditions may include: if the device is configured in a constant current mode of operation and the load opens, or if in the standard application the feedback resistors are disconnected from the circuit. In these cases the FB pin will pull to ground, causing the MIC2295 to switch with a high dutycycle. As a result, the output voltage will climb out of regulation, causing the SW pin to exceed its maximum voltage rating and possibly damaging the IC and the external components. To ensure the highest level of safety, the MIC2295 has a dedicated pin, OVP, to monitor and clamp the output voltage in over-voltage conditions. The OVP function is offered in the 2mm x 2mm MLF-8L package option only. To disable OVP function, tie the OVP pin to ground 10 M9999-052402 (408) 955-1690
Where Vref is equal to 1.24V.
Duty-Cycle The MIC2295 is a general-purpose step up DC-DC converter. The maximum difference between the input voltage and the output voltage is limited by the maximum duty-cycle (Dmax) of the converter. In the case of MIC2295, DMAX = 85%. The actual duty cycle for a given application can be calculated as follows:
VIN VOUT The actual duty-cycle, D, cannot surpass the maximum rated duty-cycle, Dmax. D =1
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MIC2295
VIN 3V to 4.2V
L1 10H
D1
VOUT 9V @ 180mA
MIC2295BML C1 2.2F 10V VIN SW OVP EN GND GND FB R2 5k R1 31.6k C2 4.7F 16V
GND
3.3VIN to 5VOUT @ 400mA
VIN 3V to 4.2V L1 10H D1 VOUT 12V @ 120mA
3VIN - 4.2VIN to 9VOUT @ 180mA
VIN 3V to 5V L1 10H D1 VOUT 12V @ 120mA
MIC2295BML C1 2.2F 10V VIN SW OVP EN GND GND FB R2 5k R1 43.2k C2 4.7F 16V
MIC2295BML C1 2.2F 10V VIN SW OVP EN GND
GND
R1 43.2k
FB R2 5k
C2 4.7F 16V
GND
GND
3VIN - 4.2Vin to 12VOUT @ 120mA
VIN 3V to 5V L1 10H D1 VOUT 12V @ 120mA
VIN 3V to 4.2V
3VIN - 5VIN to 12VOUT @ 120mA
L1 4.7H D1 VOUT 5V @ 400mA 470 pF R1 5.62k C2 4.7F 16V R2 1.87k
MIC2295BML C1 2.2F 10V VIN SW OVP EN GND GND FB R2 5k R1 43.2k C2 2.2F 16V
C1 4.7F 6.3V
MIC2295BML VIN SW OVP EN GND FB
GND
GND
GND
3VIN - 5VIN to 12VOUT @ 120mA
VIN 3V to 5V L1 10H D1 VOUT 12V @300mA
3VIN - 4.2VIN to 5VOUT @ 400mA
VIN 5V L1 10H D1 VOUT 24V@80mA
MIC2295BML C1 2.2F 10V VIN SW OVP EN GND GND FB R2 5k R1 43.2k C2 4.7F 16V
MIC2295BML C1 2.2F 10V VIN SW OVP EN GND
GND
R1 43.2k
FB R2 5k
C2 2.2F 25V
GND
GND
3VIN to 5VIN to 12VOUT @ 300mA
5VIN to 24VOUT @ 80mA
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MIC2295
Package Information
8-Pin Package MLF (ML)
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MIC2295
MICREL, INC. 1849 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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