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| LM3409MY-NOPB Datasheet, PDF (20/43 Pages) Texas Instruments – PFET Buck Controller for High Power LED Drivers | |||
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LM3409, LM3409HV, LM3409-Q1
SNVS602J â MARCH 2009 â REVISED MAY 2013
TYPICAL APPLICATION
Design Guide
RUV2
www.ti.com
RUV1
1
UVLO
2
IADJ
10
VIN
CF
9
VCC
VIN
CIN
ROFF
COFF
3
EN
LM3409/HV
8
CSP
4
COFF
5
GND
DAP
7
CSN
6
PGATE
RSNS
Q1
L1
D1
VO
ILED
SPECIFICATIONS
Nominal input voltage: VIN
Maximum input voltage: VIN-MAX
Nominal output voltage (# of LEDs x forward voltage): VO
LED string dynamic resistance: rD
Switching frequency (at nominal VIN, VO): fSW
Average LED current: ILED
Inductor current ripple: ÎiL-PP
LED current ripple: ÎiLED-PP
Input voltage ripple: ÎvIN-PP
UVLO characteristics: VTURN-ON and VHYS
Expected efficiency: η
1. NOMINAL SWITCHING FREQUENCY
Calculate switching frequency (fSW) at the nominal operating point (VIN and VO). Assume a COFF value (between
470pF and 1nF) and a system efficiency (η). Solve for ROFF:
20
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Copyright © 2009â2013, Texas Instruments Incorporated
Product Folder Links: LM3409 LM3409HV LM3409-Q1
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