LM3209-G3_16 Datasheet, PDF (15/22 Pages) Texas Instruments – Seamless-Transition Buck-Boost Converter

LM3209-G3
www.ti.com
SNVS626B – NOVEMBER 2009 – REVISED MARCH 2013
APPLICATION INFORMATION
SETTING THE OUTPUT VOLTAGE
The LM3209-G3 features a pin-controlled variable output voltage which eliminates the need for external feedback
resistors. It can be programmed for an output voltage from 0.6V to 4.2V by setting the voltage on the VCON pin,
as in the following formula.
V_OUT = 3 x VCON
(1)
When VCON is between 0.2V and 1.4V, the output voltage will follow this formula.
Internally, VCON is clamped to avoid exceeding the maximum output voltage. When the VCON voltage is greater
than 1.6V, the output voltage is regulated at approximately 4.8V.
OUTPUT CURRENT CAPABILITY
The LM3209-G3 is designed for a maximum load capability of 650 mA when V_IN ≥ 3.0V and 500 mA when V_IN <
3.0V.
V_OUT
4.2V
4.2V
3.6V
Table 1. Output Voltage vs. Maximum Output Current
V_IN
> 3.0V
≤ 3.0V
≥ 3.2V
Maximum I_OUT
650 mA
500 mA
1000 mA
RECOMMENDED EXTERNAL COMPONENTS
INDUCTOR SELECTION
A 2.2 µH inductor with a saturation current rating over 1900 mA and low inductance drop at the full DC bias
condition is recommended for almost all applications. An inductor with a DC resistance of less than 0.1Ω and
lower ESR should be used to get good efficiency for the entire output current range.
If an inductance with a lower I_SAT rating is used in the application, the VCON Transient Response time will be
affected. The rise time of the output voltage will be increased because the inductor will saturate and cannot
charge the output capacitor quickly enough. If a winding type inductor is selected, the efficiency in light load
conditions may be degraded due to higher ESR losses.
Vendor
FDK
Murata
Samsung
Table 2. Suggested Inductors (2.2 µH)
Part Number
MIPSZ2520D2R2 (2.2 µH)
LQH2HPN1R0NG0
CIG22H2R2MNE
Dimensions (mm)
2.5 x 2.0 x 1.0
2.5 x 2.0 x 1.2
2.5 x 2.0 x 1.2
I_SAT (30%)
1.5A
1.8A
1.9A
I_RATING(Δ40°C)
1.1A
1.1A
1.6A
DCR (mΩ)
110
115
116
INPUT CAPACITOR SELECTION
A ceramic input capacitor of 10 µF, 6.3V or higher is sufficient for most applications. Place the input capacitor as
close as possible to the PV_IN and PGND pins of the device. A larger value or higher voltage rating may be used
to improve input filtering. Use X7R, X5R, or B types; do not use Y5V or F. DC bias characteristics of ceramic
capacitors must be considered when selecting case sizes like 0603(1608), 0805(2012), or smaller profile. The
input filter capacitor supplies current to the PMOS switch in the first half of each cycle and reduces the voltage
ripple imposed on the input power source. A ceramic capacitor's low ESR provides the best noise filtering of
input voltage spikes caused by this rapidly changing current.
Copyright © 2009–2013, Texas Instruments Incorporated
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