LM3450MT/NOPB National Semiconductor, LM3450MT/NOPB Datasheet - Page 20

• Manufacturer Part Number: LM3450MT/NOPB
• Description: IC LED DRIVER DIMMING 16-TSSOP
• Manufacturer: National Semiconductor

Specifications of LM3450MT/NOPB

• Featured Product: LM3450 LED Driver
• Internal Driver: No
• Type - Primary: General Purpose
• Type - Secondary: High Brightness LED (HBLED)
• Mounting Type: Surface Mount
• Topology: PWM
• Number Of Outputs: 1
• Voltage - Supply: 8.5 V ~ 20 V
• Voltage - Output: 11.5V
• Package / Case: 16-TSSOP (0.173", 4.40mm Width)
• Operating Temperature: -40°C ~ 125°C
• Led Driver Application: General Lighting
• No. Of Outputs: 1
• Output Current: 200mA
• Output Voltage: 11.5V
• Input Voltage: 8.5V To 20V
• Dimming Control Type: PWM / Analog
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Frequency: -

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The dynamic hold will quickly bleed off the excess charge in
an attempt to regulate the voltage across RSEN. This will
preserve the accuracy of the decoded phase angle.
During the conduction angle (θ), dynamic hold is enabled only
during a sample period. However, during the firing angle (de-
lay time), dynamic hold is always enabled to ensure the
rectified line voltage does not begin to rise due to leakage
currents through the phase dimmer.
The minimum regulated input current can be calculated:
FIGURE 17. Reverse Phase Waveforms
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The maximum possible additional holding current (which can
occur when HOLD is still transitioning usually at the rising
edge of the triac firing) can be approximated:
It is recommended that the maximum hold current is set
10-15% higher than the minimum regulated input current.
A minimum of 0.1µF capacitance should be placed between
I
cuit to well below the switching frequency. However, if too
large a capacitor is used, the bandwidth will be too low to re-
spond to line transients. A maximum of 0.47µF should ensure
good performance.
Finally, a small Schottky diode should be placed from GND to
I
triac firing edge. This diode should have a VF above 200mV
at the worst-case operating temperature so that it won’t inter-
fere with dynamic hold regulation.
SEN
SEN
and HOLD to limit the bandwidth of the dynamic hold cir-
to absorb the large current spikes associated with the