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UNISONIC TECHNOLOGIES CO., LTD L3380
PWM STEP UP DC-DC CONTROLLER
DESCRIPTION
The L3380 is PWM step up DC-DC switching controller that operates from 0.9V. The low start up input voltage makes L3380 specially designed for powering portable equipment from one or two cells battery packs. This device consist of a soft start circuit, a reference voltage source, an error amplifier, an oscillator, a phase compensation, a PWM controller and an output drive circuit for driving external power transistor. Additionally, a chip enable feature is provided to power down the converter for extended battery life. The device features a voltage mode PWM control loop, providing stable and high efficiency operation over a broad load current range.
2 1
CMOS IC
3
5 4
SOT-25
*Pb-free plating product number: L3380L
FEATURES
* 0.9V low start-up Input voltage at 1mA load * Low operation current * 0.5uA low shutdown current * Fix requency PWM at 100KHZ * Built in PWM switching control circuit ,duty ratio is 0~83% * Output voltage:0.1V step setting is available between 2.0V and 6.5V * Soft start time: 6ms * Shutdown function
APPLICATIONS
*Portable devices *Electronic games *Portable audio (MP3) *Personal digital assistant (PDA) *Digital still cameras(DSC) *Camcorders *White LED driver *Single and dual-cell battery operated products
ORDERING INFORMATION
Order Number Normal Lead Free Plating L3380-xx-AF5-R L3380L-xx-AF5-R Package SOT-25 Packing Tape Reel
L3380L-xx-AF5-R (1)Packing Type (2)Package Type (3)Output Voltage Code (4)Lead Plating (1) R: Tape Reel (2) AF5: SOT-25 (3) xx: refer to Marking Information (4) L: Lead Free Plating Blank: Pb/Sn ,
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MARKING INFORMATION
PACKAGE VOLTAGE CODE 18:1.8V 21:2.1V 25:2.5V 27:2.7V 30:3.0V 33:3.3V 40:4.0V 50:5.0V MARKING
3 2 1
CMOS IC
SOT-25
H0
Voltage Code Lead Plating
4
5
PIN DESCRIPTION
PIN 1 2 3 4 5 NAME SHUTDOWN VOUT NC VSS EXT FUNCTION Shutdown control input, "H" : normal operation "L" : stop step up( whole circuit stop). Power supply and voltage output. No connection. Ground. Switching the circuit by connecting to a transistor.
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BLOCK DIAGRAM
VOUT 2 L3380
CMOS IC
Error Amp PWM COMP Phase compensation Voltage Reference Oscillator Soft Start Driver 5 EXT
4 VSS
1 SHUTDOWN
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ABSOLUTE MAXIMUM RATINGS
CMOS IC
PARAMETER SYMBOL RATINGS UNIT VOUT Pin Voltage VOUT 12 V SHUTDOWN Pin Voltage VSHUTDOWN VSS-0.3~12 V EXT Pin Voltage VEXT -0.3~ VOUT+0.3 V EXT Pin Current IEXT 80 mA Power Dissipation PD 250 mW Operating Ambient Temperature TOPR -40~+85 Storage Temperature TSTG -40~ +125 Note: Absolute maximum ratings are those values beyond which the device could be permanently damaged. Absolute maximum ratings are stress ratings only and functional device operation is not implied.
ELECTRICAL CHARACTERISTICS
Refer to the test circuit, TOPR=25C VIN=VOUT (S)*0.6, IOUT=VOUT (S)/50 , unless otherwise specified. PARAMETER TOTAL DEVICE Output Voltage Supply Current 1 Supply Current 2 Input Voltage Operation Holding Voltage Operation Start Voltage Oscillation Start Voltage Oscillation Frequency Duty Ratio Line Regulation Load Regulation Temperature Coefficient Efficiency Soft Start time SHUTDOWN Shutdown Supply Current Shutdown Pin Input Current VOUT IS1 IS2 VIN VHOLD VST1 VST2 fOSC Duty LNR LDR ET EF Ts ISS ISH ISL VIH Shutdown Pin Input Voltage Threshold VIL1 V IL2 EXT EXT Pin Current IEXTH IEXTL 1 1 VEXT=VOUT (S) -0.4V VEXT= 0.4V -16.1 27.4 -32.3 54.8 mA mA 1 2 1 1 2 2 2 1 1 1 2 2 2 2 2 1 1 VSHUTDOWN=0 VSHUTDOWN=VOUT (S)*0.95 VSHUTDOWN=0 Shutdown pin "L" to "H" until EXT output oscillating signal Shutdown pin VOUT 1.5V "H" to "L" until EXT output oscillating signal VOUT 1.5V VOUT=VOUT (S)*0.95 VOUT=VIN (S)+0.5V Measured by decreasing VIN voltage gradually, when IOUT=1mA. IOUT=1mA Increase the VIN until EXT pin output the oscillating signal VOUT=VOUT (S)*0.95 VOUT=VOUT (S)*0.95 VIN=VOUT (S)*0.4 to *0.6 IOUT=10uA to VOUT (S)/50*1.25 VOUT/( TOPR*VOUT) TOPR=-40 to +85
VOUT (S)*0.976 VOUT (S) VOUT (S)*1.024
SYMBOL
TEST CIRCUIT
TEST CONDITION
MIN
TYP
MAX
UNIT
V uA uA V V
39.8 6.3
66.4 12.5 10
0.7 0.9 0.8 85 75 100 83 30 30 50 3.0 86 6.0 12.0 0.5 0.1 -0.1 0.75 0.3 0.2 115 90 60 60
V V KHZ % mV mV ppm/ % ms uA uA uA V V V
Note: VOUT (S) is the value of the set output voltage.
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APPLICATION CIRCUIT
L1
CMOS IC
CDRH8D28-470
D1 M1FH3
VOUT
C2
VIN
C1
Q1 FDN335N R1
EXT
L3380
SHUTDOWN
C3 F93
OUT
VSS
TEST CIRCUIT
1.
Oscilloscope
SHUTDOWN
EXT VOUT + VSS 0.1u 47u VIN + -
+ -
2.
VIN
+ -
+ -
47u
EXT VOUT
SHUTDOWN
+ 0.1u 47u -
v
VSS
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APPLICATION CIRCUIT INFORMATION
The following equations show the relation of the basic design parameters.
CMOS IC
1. Refer to the application circuit, the increasing inductor current when the switch is turn on is given by the following equation
iL + =
1 1 d U LTON = (U IN - U S ) L L f
( U IN :input voltage ;
U S :transistor saturation voltage)
1 1 1- d U LTOFF = - (U O + U D - U IN ) U D diode forward voltage L L f + - according to iL + iL = 0 ,the duty ratio is given by U + U D - U IN d= O UO + U D - U S IO 2. The average current flowing through the inductor is I L = 1- d 3. We note that I O = (1 - d ) I L I then we can write: I O = (1 - d ) L * iL iL 1 substituting iL = U LTOFF iL for equation above, output current is given by L i 1 1 I O = (1 - d ) * * U LTOFF ( ICR = L ) IL ICR L 1 1 1- d I O = (1 - d ) * * (Uo + U D - U IN ) ICR L f iL - =
The decreasing inductor current when the switch is turn off can derive by the equation below
IO =(1-d ) 2
derive that
UO+UD - UIN ICR L f
L=
(1- d) 2(UO+UD-UIN) ICR * IO * f
4. The peak current of the inductor is given by
1 I PK = I L + iL 2 1 iL I PK = I L + * IL 2 IL i according to ICR = L IL 1 I PK = I L + ICR * I L 2 1 I PK = I L (1 + ICR) 2
derive that
Then derive the following equation for peak current of inductor
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APPLICATION CIRCUIT INFORMATION (Cont.)
5. Charge stores in C3 during charging up is given by
CMOS IC
Q = I C * TOFF
we can write
Q = ( I L - I O ) *
1- d f
6. Output ripple voltage is given by
VPP = U C + ESR * ( I L - I O )
(ESR: equivalent series resistance of the output capacitor)
VPP =
Q + ESR * ( I L - I O ) C
U IN =1.5V Uo =2.1V I O =200mA VPP =100mV f=300KHZ ICR=0.2 US
are both 0.3V, the duty ratio is
Then we give the following example about choosing external components by considering the design parameters. Design parameters: Assume
UD
and
d=
U O + U D - U IN 2.1 + 0.3 - 1.5 = = 0.429 U O + U D - U S 2.1 + 0.3 - 0.3
In order to generate the desired output current and ICR, the value of inductor should meets the following formula
L
(1- d) 2(UO+UD-UIN) ICR * IO * f
=
(1- 0.429)2(2.1V+0.3V-1.5V) 0.2x0.2Ax300000HZ
= 24.5uH
Calculate the average current and the peak current of inductor
IL =
IO 0.2 A = = 0.35 A 1 - d 1 - 0.429 1 1 ICR) = 0.35 A x (1 + x 0.2) = 0.385 A 2 2
I PK = I L (1 +
So, we make a trial of choosing a 22uH inductor that allowable maximum current is lager than 0.385A. Determine the delta charge stores in C3 during charging up
Q = ( I L - I O ) *
1- d 1 - 0.429 = (0.35 A - 0.2 A) x = 0.286uC f 300000 HZ
Assume the ESR of C3 is 0.15, determine the value of C3
Q 0.286 x 10-6 C C = = 3.69uF VPP - ESR * ( I L - I O ) 0.1 - 0.15 x (0.35 A - 0.2 A)
Therefore, a Tantalum capacitor with value of 10uF and ESR of 0.15 can be used as output capacitor. However, the optimized value should be obtained by experiment.
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EXTERNAL COMPONENTS
1. Diode (D1)
CMOS IC
The diode is the largest source of loss in DC-DC converters. The most important parameters which affect the efficiency are the forward voltage drop
UD
and the reverse recovery time. The forward voltage drop creates a loss
just by having a voltage across the device while a current flowing through it. The reverse recovery time generates a loss when the diode is reverse biased, and the current appears to actually flow backwards through the diode due to the minority carriers being swept from the P-N junction. A Schottky diode with the following characteristics is recommended: *Low forward voltage:
U D < 0.3V 50nS
*Fast reverse recovery time/switching speed: *Rated current:
> I PK UO + U D
*Reverse voltage:
2. Inductor (L1) Low inductance values supply higher output current, but also increase the ripple and reduce efficiency. Choose a low DC-resistance inductor to minimize loss. It is necessary to choose an inductor with saturation current greater than the peak current that the inductor will encounter in the application. Saturation occurs when the inductor's magnetic flux density reaches the maximum level the core can support and inductance falls.
3. Capacitor (C1,C3) The input capacitor C1 improves the efficiency by reducing the power impedance and stabilizing the input current. Select a C1 value according to the impedance of the power supply used. Small Equivalent Series Resistance(ESR) Tantalum or ceramic capacitor with an appropriate value should be suitable The output capacitor is used for smoothing the output voltage and sustaining the output voltage when the switch is on. Select an appropriate capacitor depending on the ripple voltage that increases in case of a higher output voltage or a higher load current. The capacitor value should be 10uF minimum. Small ESR should be used to reduce output ripple voltage. However, the best ESR may depend on L, capacitance, wiring and applications(output load). Therefore, fully evaluate ESR under an actual condition to determine the best value.
4. External transistor (Q1 R1 C2) An enhancement N-channel MOSFET or a bipolar NPN transistor can be used as the external switch transistor. *Bipolar NPN transistor The hFE value of NPN transistor and the R1 value determine the driving capacity to increase the output current using a bipolar transistor. 1K is recommended for R1. R1 is selected from the following calculation. Calculate the necessary base current(Ib) from the bipolar transistor hFE using
Ib =
I PK hFE
R1 =
Vout - 0.7 0.4 - Ib | I EXTH |
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EXTERNAL COMPONENTS(Cont.)
CMOS IC
Since the pulse current flows through the transistor, the exact Rb value should be finely tuned by the experiment. Generally, a small Rb value can increase the output current capability, but the efficiency will decrease due to more energy is used to drive the transistor. Moreover, a speed up capacitor, C2, should be connected in parallel with R1 to reduce switching loss and improve efficiency. C2 can be calculated by the equation below:
C2
1 2 x R1x fOSC x 0.7
It is due to the variation in the characteristics of the transistor used. The calculated value should be used as the initial test value and the optimized value should be obtained by the experiment. *Enhancement MOS FET For enhancement N-channel MOSFET, since enhancement MOSFET is a voltage driven, it is a more efficient switch than a BJT transistor. However, the MOSFET requires a higher voltage to turn on as compared with BJT transistors. An enhancement N-channel MOSFET can be selected by the following guidelines: Input capacitance less than 700pF. Low gate threshold voltage. Low on-resistance. The allowable maximum current of drain should be larger than peak current of inductor.
UTC assumes no responsibility for equipment failures that result from using products at values that exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges, or other parameters) listed in products specifications of any and all UTC products described or contained herein. UTC products are not designed for use in life support appliances, devices or systems where malfunction of these products can be reasonably expected to result in personal injury. Reproduction in whole or in part is prohibited without the prior written consent of the copyright owner. The information presented in this document does not form part of any quotation or contract, is believed to be accurate and reliable and may be changed without notice.
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