UC3380 [UTC]
PWM STEP UP DC-DC CONTROLLER; PWM升压DC-DC控制器
| 型号： | UC3380 |
| 厂家： | 
Unisonic Technologies |
| 描述： | PWM STEP UP DC-DC CONTROLLER |
| 文件： | 总9页 (文件大小：274K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
UNISONIC TECHNOLOGIES CO., LTD
UC3380
CMOS IC
PWM STEP UP DC-DC
CONTROLLER
DESCRIPTION
The UC3380 is PWM step up DC-DC switching controller that
operates from 0.9V. The low start up input voltage makes UC3380
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.
FEATURES
* 0.9V Low Start-Up Input Voltage at 1mA Load
* Low Operation Current
* 0.5uA Low Shutdown Current
* Fix Frequency PWM at 300KHZ
* Built in PWM Switching Control Circuit ,Duty Ratio is 0~78%
* Output Voltage:0.1V Step Setting is Available Between 2.0V and 6.5V
* Soft Start Time: 3ms
* 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
Ordering Number
Package
SOT-25
Packing
Lead Free
Halogen Free
UC3380G-xx-AF5-R
UC3380L-xx-AF5-R
Tape Reel
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MARKING INFORMATION
PACKAGE
VOLTAGE CODE
MARKING
18:1.8V
21:2.1V
25:2.5V
27:2.7V
30:3.0V
33:3.3V
40:4.0V
50:5.0V
SOT-25
PIN DESCRIPTION
PIN NO
NAME
DESCRIPTION
Shutdown control input, “H” : normal operation
“L” : stop step up( whole circuit stop).
Power supply and voltage output.
1
SHUTDOWN
2
3
4
5
VOUT
NC
No connection.
VSS
Ground.
EXT
Switching the circuit by connecting to a transistor.
BLOCK DIAGRAM
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CMOS IC
ABSOLUTE MAXIMUM RATINGS
PARAMETER
VOUT Pin Voltage
SYMBOL
VOUT
RATINGS
12
UNIT
V
SHUTDOWN Pin Voltage
EXT Pin Voltage
VSHUTDOWN
VEXT
VSS-0.3~12
-0.3~ VOUT+0.3
±80
V
V
EXT Pin Current
IEXT
mA
mW
°C
°C
Power Dissipation
PD
250
Operating Ambient Temperature
Storage Temperature
TOPR
-40~+85
-40~ +125
TSTG
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=25°C, VIN=VOUT (S)*0.6, IOUT=VOUT (S)/50Ω, unless otherwise specified.
TEST
CIRCUIT
PARAMETER
TOTAL DEVICE
SYMBOL
VOUT
TEST CONDITION
MIN
TYP
MAX UNIT
VOUT
(S)
VOUT
VOUT
Output Voltage
2
V
(S)*0.976
(S)*1.024
VOUT (S)15 to 19
33.8
50.3
68.6
88.4
56.4
83.9
VOUT (S)20 to 29
VOUT (S)30 to 39
VOUT (S)40 to 49
VOUT (S)50 to 59
VOUT (S)60 to 65
VOUT (S)15 to 19
VOUT (S)20 to 29
VOUT (S)30 to 39
VOUT (S)40 to 49
VOUT (S)50 to 59
VOUT (S)60 to 65
114.4
uA
VOUT
=
Supply Current 1
IS1
1
1
VOUT (S)*0.95
147.4
109.4 182.4
131.6 219.3
9.7
9.9
19.4
19.7
20.0
20.4
20.7
21.0
10
10.0
10.2
10.4
10.5
VOUT
=
Supply Current 2
Input Voltage
IS2
uA
VIN (S)+0.5V
VIN
2
2
V
V
Measured by decreasing VIN
voltage gradually, when
Operation Holding Voltage VHOLD
0.7
I
OUT=1mA.
Operation Start Voltage
Oscillation Start Voltage
VST1
VST2
2
1
IOUT=1mA
0.9
0.8
V
V
Increase the VIN until EXT pin
output the oscillating signal
VOUT=VOUT (S)*0.95
Oscillation Frequency
Duty Ratio
fOSC
Duty
⊿LNR
⊿LDR
1
1
2
2
255
70
300
78
345
85
KHz
%
VOUT=VOUT (S)*0.95
Line Regulation
Load Regulation
VIN=VOUT (S)*0.4 to *0.6
IOUT=10uA to VOUT (S)/50*1.25
30
60
mV
mV
30
60
⊿VOUT/(⊿TOPR*VOUT
)
Temperature Coefficient
ET
2
±50
ppm/°C
TOPR=-40°C ~ +85°C
Efficiency
EF
Ts
2
2
85
%
Soft Start time
1.5
3.0
6.0
ms
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UC3380
CMOS IC
ELECTRICAL CHARACTERISTICS
TEST
CIRCUIT
PARAMETER
SHUTDOWN
SYMBOL
TEST CONDITION
MIN
0.75
TYP
MAX
UNIT
Shutdown Supply Current
Shutdown Pin Input
Current
ISS
ISH
ISL
1
1
VSHUTDOWN=0
0.5
0.1
uA
uA
uA
VSHUTDOWN=VOUT (S)*0.95
VSHUTDOWN=0
-0.1
Shutdown pin “L” to “H” until EXT
output oscillating signal
VIH
V
Shutdown Pin Input
Voltage Threshold
1
1
1
Shutdown pin “H” to
“L” until EXT output
oscillating signal
VIL1
VOUT≥1.5V
0.3
0.2
V
V
V IL2
VOUT<1.5V
EXT
VOUT (S)15 to 19
VOUT (S)20 to 24
VOUT (S)25 to 29
-4.5
-6.2
-8.9
-12.3
-15.7
-20.7
-26.7
-32.3
-37.7
19.0
25.2
31.0
38.5
47.6
54.8
60.6
-7.8
VEXT
V
=
IEXTH
VOUT (S)30 to 39 -10.3
VOUT (S)40 to 49 -13.3
VOUT (S)50 to 59 -16.1
VOUT (S)60 to 65 -18.9
mA
mA
OUT (S) -0.4V
EXT Pin Current
VOUT (S)15 to 19
9.5
VOUT (S)20 to 24 12.6
VOUT (S)25 to 29 15.5
VOUT (S)30 to 39 19.2
VOUT (S)40 to 49 23.8
VOUT (S)50 to 59 27.4
VOUT (S)60 to 65 30.3
IEXTL
VEXT= 0.4V
Note: VOUT (S) is the value of the set output voltage.
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APPLICATION CIRCUIT
TEST CIRCUIT
1.
2.
VIN
+
-
+
-
+
-
47u
V
EXT
47u
0.1u
VOUT
SHUTDOWN
VSS
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APPLICATION CIRCUIT INFORMATION
The following equations show the relation of the basic design parameters.
1. Refer to the application circuit, the increasing inductor current when the switch is turn on is given by the following
equation
1
1
d
+
ΔiL
=
ULTON
=
(UIN −US )
(UIN : input voltage: US : transistor saturation voltage)
L
L
f
The decreasing inductor current when the switch is turn off can derive by the equation below
1
1
1− d
f
−
ΔiL
=
ULTOFF = − (UO +UD −UIN )
(UD ：diode forward voltage)
L
L
+
−
according to ΔiL + ΔiL = 0 , the duty ratio is given by
UO +UD −UIN
d =
UO +UD −US
IO
1− d
IL
2. The average current flowing through the inductor is IL =
3. We note that IO = (1− d)IL then we can write:IO = (1− d)
• ΔiL
ΔiL
1
substituting ΔiL = ULTOFF ΔiL for equation above, output current is given by
L
1
1
L
1
L
ΔiL
IL
IO = (1− d) •
IO = (1− d) •
•
•
ULTOFF
(ICR =
)
ICR
1
ICR
U
1− d
(Uo +UD −UIN )
f
O
+UD −UIN
ICR •L •f
IO = (1− d)2 •
derive that
4. The peak current of the inductor is given by
1
IPK = IL + ΔiL
2
1 ΔiL
2 IL
IPK = IL +
•IL
ΔiL
IL
according to ICR =
derive that
1
IPK = IL + ICR •IL
2
Then derive the following equation for peak current of inductor
1
IPK = IL(1+ ICR)
2
5. Charge stores in C3 during charging up is given by ΔQ = IC •TOFF
1− d
f
we can write ΔQ = (IL − IO )•
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APPLICATION CIRCUIT INFORMATION (Cont.)
6. Output ripple voltage is given by
VPP = ΔUC + ESR •(IL − IO ) (ESR: equivalent series resistance of the output capacitor)
ΔQ
C
VPP
=
+ ESR •(IL − IO )
Then we give the following example about choosing external components by considering the design parameters.
Design parameters: UIN=1.5V UO=2.1V IO=200mA VPP=100mV f=300KHz ICR=0.2
Assume UD and US are both 0.3V, the duty ratio is
UO +UD −UIN 2.1+ 0.3 −1.5
UO +UD −US 2.1+ 0.3 − 0.3
d =
=
= 0.429
In order to generate the desired output current and ICR, the value of inductor should meets the following formula
(1– d)2(UO+UD-UIN)
(1– 0.429)2(2.1V+0.3V-1.5V)
24.5uH
=
L ≤
=
ICR • IO • f
0.2×0.2A×300000HZ
Calculate the average current and the peak current of inductor
IO
0.2A
IL =
=
= 0.35A
1− d 1− 0.429
1
1
IPK = IL(1+ ICR) = 0.35A×(1+ ×0.2) = 0.385A
2
2
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
1− d
f
1− 0.429
300000HZ
ΔQ = (IL − IO )•
= (0.35A − 0.2A)×
= 0.286uC
Assume the ESR of C3 is 0.15Ω, determine the value of C3
ΔQ
0.286×10−6C
VPP − ESR •(IL − IO ) 0.1− 0.15Ω×(0.35A − 0.2A)
C ≥
=
= 3.69uF
Therefore, a Tantalum capacitor with value of 10uF and ESR of 0.15Ω can be used as output capacitor. However,
the optimized value should be obtained by experiment.
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EXTERNAL COMPONENTS
1. Diode (D1)
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: UD<0.3V
*Fast reverse recovery time/switching speed: ≦50nS
*Rated current: >IPK
*Reverse voltage: ≧UO+UD
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. 1KΩ is recommended for R1. R1 is selected from the following calculation.
IPK
Calculate the necessary base current(Ib) from the bipolar transistor hFE using Ib =
hFE
V
OUT − 0.7
0.4
R1=
−
Ib
| IEXTH |
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:
1
C2 ≤
2π ×R1×fOSC ×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.
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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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