LM3409HVMYX/NOPB National Semiconductor, LM3409HVMYX/NOPB Datasheet - Page 9

• Manufacturer Part Number: LM3409HVMYX/NOPB
• Description: IC LED DRIVR HIGH BRIGHT 10-MSOP
• Manufacturer: National Semiconductor
• Series: PowerWise®r
• Type: HBLED Driverr

Specifications of LM3409HVMYX/NOPB

• Constant Current: Yes
• Topology: PWM, Step-Down (Buck)
• Number Of Outputs: 1
• Internal Driver: No
• Type - Primary: Automotive
• Type - Secondary: High Brightness LED (HBLED)
• Voltage - Supply: 6 V ~ 75 V
• Mounting Type: Surface Mount
• Package / Case: 10-MSOP Exposed Pad, 10-HMSOP, 10-eMSOP
• Operating Temperature: -40°C ~ 125°C
• Internal Switch(s): Yes
• Efficiency: 97%
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Output: -
• Frequency: -
• Current - Output / Channel: -
• Other names: LM3409HVMYX

CONTROLLED OFF-TIME (COFT) ARCHITECTURE
The COFT architecture is used by the LM3409/09HV to con-
trol I
one-shot off-timer that varies with output voltage. D is indi-
rectly controlled by changes in both t
depending on the operating point. This creates a variable
switching frequency over the entire operating range. This type
of hysteretic control eliminates the need for control loop com-
pensation necessary in many switching regulators, simplify-
ing the design process and providing fast transient response.
LED
. It is a combination of peak current detection and a
FIGURE 1. Ideal CCM Buck Converter Inductor Current i
OFF
and t
FIGURE 2. Peak Current Control Circuit
ON
, which vary
9
Adjustable Peak Current Control
At the beginning of a switching period, PFET Q1 is turned on
and inductor current increases. Once peak current is detect-
ed, Q1 is turned off, the diode D1 forward biases, and inductor
current decreases.
tion is accomplished using the differential voltage signal cre-
ated as current flows through the current setting resistor
(R
adjustable current sense threshold (V
off when V
the minimum possible t
SNS
). The voltage across R
SNS
exceeds V
Figure 2
ON
L
CST
(t)
(typically 115ns).
, providing that t
shows how peak current detec-
SNS
(V
30085604
SNS
CST
) is compared to the
30085605
) and Q1 is turned
ON
is greater than
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