LED5000PHR STMicroelectronics, LED5000PHR Datasheet - Page 22

• Manufacturer Part Number: LED5000PHR
• Description: Current & Power Monitors & Regulators 3A monolithic Conv 850kHz Synch
• Manufacturer: STMicroelectronics

Specifications of LED5000PHR

• Rohs: yes
• Product: Current Regulators
• Supply Voltage - Max: 48 V
• Supply Voltage - Min: 5.5 V
• Operating Temperature Range: - 40 C to + 150 C
• Mounting Style: SMD/SMT
• Package / Case: HPSO-8
• Accuracy: +/- 3 %
• Input Voltage Range: 5.5 V to 48 V
• Output Current: 23 uA
• Sensing Method: High or Low Side
• Supply Current: 1.7 mA

Application notes - buck conversion
5.8.1
22/51
Dimming frequency vs. dimming depth
As seen in
system bandwidth (T
The dimming performance depends on the minimum current pulse shape specification of
the final application. The ideal minimum current pulse has rectangular shape, in any case it
degenerates into a trapezoid or, at worst, into a triangle, depending on the ratio (T
T
Equation 23
The small signal response in
Equation 24
Assuming the minimum current pulse (T
Equation 25:
where T
gives the T
Figure 15. dimming signal
Given T
frequency or vice versa.
For example, assuming a 10 KHz dimming frequency the maximum dimming depth is 9% or
given a 5% dimming depth it follows a 5.5 KHz maximum f
The LED5000 dimming performance is strictly dependent on the system small signal
response. As a consequence, an optimized compensation network (good phase margin and
bandwidth maximized) and minimized C
FALL
)/ T
MIN_PULSE
DIMMING
DIM
T
-------------------------------------------- - 1
RISE
MIN_PULSE
Chapter 5.8
rec
T
DIM
+
tan
T
T
represents the dimming period and D
RISE
FALL
it is possible to calculate the maximum dimming depth given the dimming
gle
RISE
+
charge. In the given example T
«
T
the LEDs current rising and falling edge time mainly depends on the
FALL
) and the selected output capacitor value (T
Figure 14
Doc ID 023951 Rev 1
=
0.75
T
-------------------------------------------- -
T
RISE
is considered as an example.
trapezoid
MIN_PULSE
MIN_PULSE
OUT
T
T
FALL
T
RISE
DIM
+
value are crucial for best performance. Once
T
FALL
5 s
2 s
) shape specification as:
=
1
0.75
MIN_PULSE
MIN
the minimum duty cycle which
DIM
D
MIN
.
=9
µ
T
-------------------------------------------- -
T
s
RISE
DIMMING
RISE
triangle
T
DIM
+
T
and T
FALL
=
FALL
1
RISE
LED5000
).
AM13499v1
+