LM3500 Datasheet, PDF (1/26 Pages) National Semiconductor (TI) – Synchronous Step-up DC/DC Converter for White LED

LM3500
www.ti.com
SNVS231G – AUGUST 2003 – REVISED MAY 2013
LM3500 Synchronous Step-up DC/DC Converter for White LED Applications
Check for Samples: LM3500
FEATURES
1
•2 Synchronous Rectification, High Efficiency
and no External Schottky Diode Required
• Uses Small Surface Mount Components
• Can Drive 2-5 White LEDs in Series
– (May Function With More Low-V_F LEDs)
• 2.7V to 7V Input Range
• Internal Output Over-Voltage Protection (OVP)
Circuitry, with no External Zener Diode
Required
– LM3500-16: 15.5V OVP; LM3500-21: 20.5V
OVP.
• True Shutdown Isolation
• Input Undervoltage Lockout
• Requires Only Small Ceramic Capacitors at the
Input and Output
• Thermal Shutdown
• 0.1µA Shutdown Current
• Small 8-Bump Thin DSBGA Package
APPLICATIONS
• LCD Bias Supplies
• White LED Backlighting
• Handheld Devices
• Digital Cameras
• Portable Applications
DESCRIPTION
The LM3500 is a fixed-frequency step-up DC/DC
converter that is ideal for driving white LEDs for
display backlighting and other lighting functions. With
fully intergrated synchronous switching (no external
schottky diode required) and a low feedback voltage
(500mV), power efficiency of the LM3500 circuit has
been optimized for lighting applications in wireless
phones and other portable products (single cell Li-Ion
or 3-cell NiMH battery supplies). The LM3500
operates with a fixed 1MHz switching frequency.
When used with ceramic input and output capacitors,
the LM3500 provides a small, low-noise, low-cost
solution.
Typical Application Circuit
VIN
2.7V - 5.5V
L
22 PH
CIN
1PF
Ceramic
>1.1V
<0.3V
B1
VIN
C2
VSW
A3
NC
LM3500-16
VOUT ^C1
A2 _SHDN
FB ^B3
AGND GND
A1 C3
COUT
1PF
Ceramic
R2
24:
1
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2
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
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