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ZXSC380
Single or multi cell LED driver solution
Description
The ZXSC380 is a highly integrated single or multi cell LED driver for applications where step-up voltage conversion from a very low input voltage is required. These applications mainly operate from 1.5V or 1.2V cells. The IC generates constant current pulses that are ideal for driving single or multiple LEDs over a wide range of operating voltages. The ZXSC380 provides a simple to use, low cost, space saving and easy to layout solutions.
The ZXSC380 uses a PFM control technique to drive an internal switching transistor which has a low saturation resistance. This ensures high efficiency, even for input voltages as low as 1V.
The IC can start up under full load and operates down to an input voltage of only 0.9V typical.
The ZXSC380 is offered in the space saving SOT23 package or in die form, offering an excellent cost vs performance solution for single cell LED driving applications.
SOT23
Features |
Applications |
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80% efficiency |
• LED flashlights and torches |
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• User adjustable output current |
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LED backlights |
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Single cell operation |
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White LED driver |
•Low saturation voltage switching transistor
•Simple application circuit
•Low external component count
•SOT23 package
•Available also in die form
Pin connections |
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Typical application circuit |
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VIN |
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VCC |
1 |
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L1 |
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1 |
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3 |
GND |
VCC |
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2 |
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ZXSC380 VOUT |
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VOUT |
2 |
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GND |
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3 |
LED1 |
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Top view |
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GND |
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Issue 3 - September 2007 |
1 |
www.zetex.com |
© Zetex Semiconductors plc 2007
ZXSC380
Absolute maximum ratings
Supply voltage (VCC) |
-0.6V to 10V |
Output voltage (VOUT) |
-0.6V to 20V |
Supply current |
20mA |
Output switch current |
200mA |
Power dissipation SOT23-3 |
450mW |
Power dissipation die |
1W |
Operating temperature range |
0°C to +85°C |
Storage temperature range |
-55°C to +150°C |
Electrical characteristics
Measured at Tamb = 25°C, L = 100 H and VCC = 1.5V unless otherwise specified.
Parameter |
Conditions |
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Limits |
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Units |
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Min. |
Typ. |
Max. |
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Supply voltage operating range |
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0.8 |
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6 |
V |
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Minimum supply start-up voltage |
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0.9 |
1.0 |
V |
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Switch current |
VOUT = 1.0V |
65 |
80 |
95 |
mA |
Switch saturation voltage |
IVOUT = 50mA |
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0.3 |
0.5 |
V |
Mean LED current |
VLED = 3.5V |
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18 |
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mA |
Efficiency |
VLED = 3.5V |
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75 |
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% |
Operating frequency |
VLED = 3.5V |
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160 |
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kHz |
Discharge pulse width |
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1.4 |
2.2 |
3.0 |
s |
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Pin descriptions
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VCC |
1 |
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3 |
GND |
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VOUT |
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2 |
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Top view |
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Pin descriptions |
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Pin No. |
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Name |
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Description |
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1 |
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VCC |
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Supply voltage, generally Alkaline, NiMH or NiCd single cell |
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2 |
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VOUT |
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Switch output external inductor/LED |
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3 |
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GND |
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Ground |
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Ordering information
Device |
Package |
Part Mark |
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ZXSC380FH |
SOT23 |
380 |
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Issue 3 - September 2007 |
2 |
www.zetex.com |
|
© Zetex Semiconductors plc 2007
ZXSC380
Typical characteristics
LED Current vs Supply Voltage for L = 100uH
(mA) |
80 |
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70 |
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60 |
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ILed |
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50 |
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Current, |
40 |
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30 |
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20 |
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LED |
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10 |
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0 |
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0.5 |
1 |
1.5 |
2 |
2.5 |
3 |
Supply Voltage Vvcc (V)
Efficiency vs Supply Voltgae for L = 100uH
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100 |
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90 |
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(%) |
80 |
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70 |
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60 |
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Efficiency |
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50 |
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40 |
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30 |
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20 |
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10 |
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0 |
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0.5 |
1 |
1.5 |
2 |
2.5 |
3 |
Supply Voltage Vvcc (V)
Ivcc vs Supply Voltage for L = 100uH
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100 |
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90 |
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80 |
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(mA) |
70 |
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60 |
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50 |
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Ivcc |
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40 |
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30 |
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20 |
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10 |
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0 |
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0.5 |
1 |
1.5 |
2 |
2.5 |
3 |
Supply Voltage Vvcc (V)
Operating Waveforms
Channel 1 (lower): LED current ILed. 50mA/div.
Channel 2 (upper): Voltage at Vout pin. 1V/div
Issue 3 - September 2007 |
3 |
www.zetex.com |
© Zetex Semiconductors plc 2007
ZXSC380
Typical characteristics
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LED Current vs Supply Voltage |
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for L = 22, 47, 68 & 100uH |
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20 |
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18 |
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(mA) |
16 |
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14 |
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ILed |
12 |
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10 |
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Current |
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8 |
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LED |
6 |
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4 |
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2 |
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0 |
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1 |
1.1 |
1.2 |
1.3 |
1.4 |
1.5 |
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Supply Voltage Vvcc (V) |
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L = 100uH |
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L = 68uH |
L = 47uH |
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L = 22uH |
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Frequency vs Supply Voltage |
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for L= 22, 47, 68 & 100uH |
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350 |
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300 |
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(kHz) |
250 |
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200 |
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Frequency |
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150 |
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100 |
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50 |
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0 |
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1 |
1.5 |
2 |
2.5 |
3 |
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Supply Voltage Vcc (V) |
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L = 100uH |
L = 68uH |
L = 47uH |
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L = 22uH |
LED Current vs Supply Voltage for L= 22, 47, 68 & 100uH
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80 |
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70 |
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(mA) |
60 |
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50 |
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ILed |
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40 |
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Current |
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30 |
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LED |
20 |
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10 |
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0 |
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1 |
1.5 |
2 |
2.5 |
3 |
Supply Voltage Vvcc (V)
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L = 100uH |
L = 68uH |
L = 47uH |
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L=22uH |
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Efficiency vs Supply Voltage |
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for L= 22, 47, 68 & 100uH |
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120 |
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100 |
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(%) |
80 |
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Efficiency |
60 |
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40 |
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20 |
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0 |
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1 |
1.5 |
2 |
2.5 |
3 |
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Supply Voltage Vvcc (V) |
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L = 100uH |
L = 68uH |
L = 47uH |
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L = 22uH |
Issue 3 - September 2007 |
4 |
www.zetex.com |
© Zetex Semiconductors plc 2007