LM3509SDEV National Semiconductor, LM3509SDEV Datasheet - Page 16
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LM3509SDEV
Manufacturer Part Number
LM3509SDEV
Description
BOARD EVALUATION FOR LM3509SD
Manufacturer
National Semiconductor
Series
PowerWise®r
Specifications of LM3509SDEV
Current - Output / Channel
40mA
Outputs And Type
2, Non-Isolated
Voltage - Output
21V
Features
Dimmable, I²C Interface
Voltage - Input
2.7 ~ 5.5V
Utilized Ic / Part
LM3509
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
www.national.com
TABLE 3. Operational Truth Table
* ENM ,ENS, or OLED high enables analog circuitry.
BRIGHTNESS REGISTERS (BMAIN and BSUB)
With the UNI bit (General Purpose register) set to 0 (Non-
Unison mode) both brightness registers (BMAIN and BSUB)
independently control the LED currents I
spectively. BMAIN and BSUB are both 8 bit, but with only the
5 LSB’s controlling the current. The three MSB’s are don’t
cares. The LED current control is designed to approximate an
exponentially increasing response of the LED current vs in-
creasing code in either BMAIN or BSUB (see Figure 9).
Program I
to GND, where:
UNI
X
X
X
1
1
0
0
0
LED_MAX
by connecting a resistor (RSET) from SET
OLED
0
0
0
0
0
0
1
1
ENM
0
1
0
0
1
1
1
0
FIGURE 7. Brightness MAIN Register Description
FIGURE 8. Brightness SUB Register Description
MAIN
and I
ENS
SUB/FB
X
X
X
X
0
1
0
1
re-
SUB/FB current sink disabled (SUB/FB configured as a feedback
SUB/FB current sink disabled (SUB/FB configured as a feedback
MAIN and SUB/FB current sinks enabled. Current levels set by
MAIN and SUB/FB current sinks enabled. Current levels set by
16
pin). MAIN current sink enabled current level set by BMAIN.
SUB/FB current sink enabled. Current level set by BSUB.
MAIN current sink enabled. Current level set by BMAIN.
. With the UNI bit (General Purpose register) set to 1 (Unison
mode), BSUB is disabled and BMAIN sets both I
FB
FB
cally 1%(with UNI = 0) to typically 0.15% (with UNI = 1). Figure
7 and Figure 8 show the register descriptions for the Bright-
ness MAIN and Brightness SUB registers. Table 4 and Figure
9 show I
age of I
. This prevents the independent control of I
, however matching between current sinks goes from typi-
contents of BMAIN and BSUB respectively.
LED_MAX
MAIN
pin). MAIN current sink disabled.
MAIN and SUB/FB Disabled
and/or I
.
contents of BMAIN.
LM3509 Disabled
SUB/FB
Result
vs. brightness data as a percent-
30004343
30004342
MAIN
MAIN
and I
and I
SUB/
SUB/