lm2758tlx National Semiconductor Corporation, lm2758tlx Datasheet - Page 9

• Manufacturer Part Number: lm2758tlx
• Description: Switched Capacitor Flash Led Driver In Micro Smd
• Manufacturer: National Semiconductor Corporation

ANALOG BRIGHTNESS CONTROL
The current though the LED could be varied dynamically by
changing the I
The current though the LED can be calculated as follows.
CAPACITOR SELECTION
The LM2758 requires 4 external capacitors for proper opera-
tion. Surface-mount multi-layer ceramic capacitors are rec-
ommended. These capacitors are small, inexpensive and
have very low equivalent series resistance (ESR <20 mΩ
typ.). Tantalum capacitors, OS-CON capacitors, and alu-
minum electrolytic capacitors are not recommended for use
with the LM2758 due to their high ESR, as compared to ce-
ramic capacitors. For most applications, ceramic capacitors
with X7R or X5R temperature characteristic are preferred for
use with the LM2758. These capacitors have tight capaci-
2.2 µF for C
1 µF for C1 and C2
C1608X5R0J225
C1608X5R0J105
JMK107BJ105M
JMK107BJ225
MFG Part No.
IN
SET
and C
current. The above figure shows the circuit.
OUT
Ceramic X5R
Ceramic X5R
Ceramic X5R
Ceramic X5R
Type
Suggested Capacitors and Suppliers
30045317
9
Taiyo-Yuden
Taiyo-Yuden
MFG
tance tolerance (as good as ±10%) and hold their value over
temperature (X7R: ±15% over -55°C to 125°C; X5R: ±15%
over -55°C to 85°C). Capacitors with Y5V or Z5U temperature
characteristic are generally not recommended for use with the
LM2758. Capacitors with these temperature characteristics
typically have wide capacitance tolerance (+80%, -20%) and
vary significantly over temperature (Y5V: +22%, -82% over
-30°C to +85°C range; Z5U: +22%, -56% over +10°C to +85°
C range). Under some conditions, a nominal 1 μF Y5V or Z5U
capacitor could have a capacitance of only 0.1 μF. Such detri-
mental deviation is likely to cause Y5V and Z5U capacitors to
fail to meet the minimum capacitance requirements of the
LM2758. The voltage rating of the output capacitor should be
6.3V or more. For example, a 6.3V 0603 2.2 μF output ca-
pacitor (TDK C1608X5R0J225) is acceptable for use with the
LM2758, as long as the capacitance on the output does not
fall below a minimum of 1 μF in the intended application. All
other capacitors should have a voltage rating at or above the
maximum input voltage of the application and should have a
minimum capacitance of 1 μF.
TDK
TDK
Voltage Rating
6.3V
6.3V
6.3V
6.3V
30045318
0603 (1608)
0603 (1608)
0603 (1608)
0603 (1608)
Inch (mm)
Case Size
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