LP3954 Datasheet, PDF (36/60 Pages) National Semiconductor (TI) – Advanced Lighting Management Unit

LP3954
SNVS340D – JUNE 2005 – REVISED MARCH 2013
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SDA
8
SCL
1
7
6
2
8
1
5
3
4
Figure 42. I²C Timing Diagram
10
7
9
I²C Timing Parameters (V_DD1,2 = 3.0 to 4.5V, V_{DD_IO} = 1.65V to V_DD1,2)
Symbol
1
2
3
4
5
5
6
7
8
9
10
C_b
Parameter
Hold Time (repeated) START Condition
Clock Low Time
Clock High Time
Setup Time for a Repeated START Condition
Data Hold Time (Output direction, delay generated by LP3954)
Data Hold Time (Input direction, delay generated by the Master)
Data Setup Time
Rise Time of SDA and SCL
Fall Time of SDA and SCL
Set-up Time for STOP condition
Bus Free Time between a STOP and a START Condition
Capacitive Load for Each Bus Line
Limit ⁽¹⁾
Min
Max
Unit
0.6
µs
1.3
µs
600
ns
600
ns
300
900
ns
0
900
ns
100
ns
20+0.1C_b
300
ns
15+0.1C_b
300
ns
600
ns
1.3
µs
10
200
pF
(1) NOTE: Data ensured by design
Autoincrement mode is available, with this possible read or write few byte with autoincreasing addresses, but
LP3954 has holes in address register map, and is recommended to use autoincrement mode only for the pattern
command registers.
Recommended External Components
OUTPUT CAPACITOR, C_OUT
The output capacitor C_OUT directly affects the magnitude of the output ripple voltage. In general, the higher the
value of C_OUT, the lower the output ripple magnitude. Multilayer ceramic capacitors with low ESR are the best
choice. At the lighter loads, the low ESR ceramics offer a much lower Vout ripple that the higher ESR tantalums
of the same value. At the higher loads, the ceramics offer a slightly lower Vout ripple magnitude than the
tantalums of the same value. However, the dv/dt of the Vout ripple with the ceramics is much lower that the
tantalums under all load conditions. Capacitor voltage rating must be sufficient, 10V or greater is recommended.
Some ceramic capacitors, especially those in small packages, exhibit a strong capacitance reduction
with the increased applied voltage. The capacitance value can fall to below half of the nominal
capacitance. Too low output capacitance will increase the noise and it can make the boost converter
unstable.
INPUT CAPACITOR, C_IN
The input capacitor C_IN directly affects the magnitude of the input ripple voltage and to a lesser degree the V_OUT
ripple. A higher value C_IN will give a lower V_IN ripple. Capacitor voltage rating must be sufficient, 10V or greater is
recommended.
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