VIN (V)

100

90

80

70

60

50

2.7

3.1

3.5

3.9

4.3

4.7

5.1

5.5

VLED = 3.6V

VLED = 3.3V

VLED = 3.0V

4 LEDs @ 25 mA each

VIN (V)

180

170

160

150

140

130

120

110

100

90

80

2.7

3.1

3.5

3.9

4.3

4.7

5.1

5.5

VLED = 3.6V

VLED = 3.3V

VLED = 3.0V

4 LEDs @ 25 mA Each

27

LM3535

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SNVS598B – AUGUST 2010 – REVISED MARCH 2018

Product Folder Links: LM3535

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8.2.2.7 Thermal Protection

Internal thermal protection circuitry disables the LM3535 when the junction temperature exceeds 150°C (typical).

This feature protects the device from being damaged by high die temperatures that might otherwise result from

excessive power dissipation. The device recovers and operates normally when the junction temperature falls

below 125°C (typical). It is important that the board layout provide good thermal conduction to keep the junction

temperature within the specified operating ratings.

8.2.2.8 Capacitor Selection

The LM3535 requires 4 external capacitors for proper operation (C1 = C2 = CIN = COUT = 1 µF). Surface-mount

multi-layer ceramic capacitors are recommended. These capacitors are small, inexpensive and have very low

equivalent series resistance (ESR < 20 m

Ω typical). Tantalum capacitors, OS-CON capacitors, and aluminum

electrolytic capacitors are not recommended for use with the LM3535 due to their high ESR, as compared to

ceramic capacitors.

For most applications, ceramic capacitors with X7R or X5R temperature characteristic are preferred for use with

the LM3535. These capacitors have tight capacitance 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 LM3535.

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 1µF Y5V or Z5U capacitor could have a capacitance

of only 0.1 µF. Such detrimental deviation is likely to cause Y5V and Z5U capacitors to fail to meet the minimum

capacitance requirements of the LM3535.

The recommended voltage rating for the capacitors is 10 V to account for DC bias capacitance losses.

8.2.3 Application Curves

Figure 37. Input Current vs Input Voltage 4 LEDs

Figure 38. LED Drive Efficiency vs Input Voltage 4 LEDs