CAT37TDI-TE7 ON Semiconductor, CAT37TDI-TE7 Datasheet - Page 7

• Manufacturer Part Number: CAT37TDI-TE7
• Description: LED Drivers White LED Boost
• Manufacturer: ON Semiconductor

Specifications of CAT37TDI-TE7

• Number Of Segments: 4
• High Level Output Current: 40 mA
• Operating Supply Voltage: 2.5 V to 7 V
• Maximum Supply Current: 0.7 mA
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Package / Case: TSOT-23-5
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Application Information
Capacitor Selection
be used at the output to minimize the output ripple voltage.
The low ESR and small package options available with
multilayer ceramic capacitors make them excellent choices.
The X5R and X7R capacitor types are preferred because
they retain their capacitance over wider voltage and
temperature ranges than the Y5V or Z5U types. A 1.0 mF
output capacitor is recommended for most applications.
the number of LEDs driven in the series. A 16 V ceramic
capacitor is recommended when driving 3 or 4 LEDs.
height/thickness
requirements. Ceramic capacitors also make a good choice
for the input capacitor, which should be mounted as close as
possible to the CAT37. A 1 mF or 4.7 mF input capacitor is
recommended. Table 5 shows a list of several ceramic
capacitor manufacturers. Consult the manufacturers for
detailed information as new products and package options
are introduced regularly.
Diode Selection
fast switching speed, are the ideal choice for high efficiency
applications. Table 6 shows several different Schottky
diodes that work well with the CAT37. Make sure that the
diode has a voltage rating greater than the output voltage.
The diode conducts current only when the power switch is
turned off (typically less than one−third the time), so a 0.4 A
or 0.5 A diode will be sufficient for most designs.
Table 5. CERAMIC CAPACITOR MANUFACTURERS
Taiyo Yuden
Murata
Kemet
AVX
Low ESR (equivalent series resistance) capacitors should
The voltage rating of the output capacitor C2 depends on
Low profile ceramic capacitors with a 1 mm maximum
Schottky diodes, with their low forward voltage drop and
Supplier
are
available
www.t−yuden.com
www.murata.com
www.kemet.com
www.avxcorp.com
for
Web
designs
http://onsemi.com
height
7
LED Current Programming
connected to the FB pin. The FB pin is internally regulated
to 95 mV, which sets the current flowing through R1 and the
LEDs as equal to 0.095/R1. For the best accuracy, a 1% or
better resistor is recommended. Table 7 shows several
typical 1% R1 values.
to choose R1.
15 mA to 20 mA. Some higher power designs will use two
parallel strings of LEDs for greater light output, resulting in
30 mA to 40 mA (two strings of 15 mA to 20 mA) flowing
through the R1 resistor.
Table 6. SCHOTTKY DIODE SUPPLIERS
Table 7. R1 RESISTOR VALUES
MBR0520
MBR0530
MBR0540
The LED current is programmed with a single resistor
For other LED current values, use the following equation
Most white LEDs are driven at maximum currents of
I
LED
Part
40
30
20
15
12
10
5
(mA)
R1 + 0.095
ON Semiconductor
www.onsemi.com
800.282.9855
I
LED
Supplier
R1 (W)
2.37
3.16
4.75
6.34
7.87
9.53
19.1