LM2758

RSET

ISET

PGND SGND

EN1

EN2

VIN

C1

+

C2

+

C2

-

C1

-

CPOUT

LED-

+

-

2.7 V to 5.5 V

C2

C1

CIN

COUT

Copyright © 2016, Texas Instruments Incorporated

11

LM2758

www.ti.com

SNVS551E – APRIL 2008 – REVISED MAY 2016

Product Folder Links: LM2758

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Copyright © 2008–2016, Texas Instruments Incorporated

8 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component

specification, and TI does not warrant its accuracy or completeness. TI’s customers are

responsible for determining suitability of components for their purposes. Customers should

validate and test their design implementation to confirm system functionality.

8.1 Application Information

The LM2758 can drive one flash LED at currents up to 700 mA. The multi-gain charge-pump boost regulator

allows for the use of small value discrete external components.

8.2 Typical Application

Figure 8. LM2758 Typical Application

8.2.1 Design Requirements

For typical switched-capacitor LED-driver applications, use the parameters listed in Table 2.

Table 2. Design Parameters

DESIGN PARAMETER

EXAMPLE VALUE

Minimum input voltage

2.7 V

Maximum output current

700 mA

8.2.2 Detailed Design Procedure

8.2.2.1 Capacitor Selection

The LM2758 device requires 4 external capacitors for proper operation. 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 LM2758 due to their high ESR compared to ceramic

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

for use with the LM2758. Ceramic 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 LM2758. Capacitors with

these temperature characteristics typically have wide capacitance tolerance (+80%, –20%) and vary significantly