EVALED7706 STMicroelectronics, EVALED7706 Datasheet - Page 20

• Manufacturer Part Number: EVALED7706
• Description: EVALUATION BOARD FOR LED7706
• Manufacturer: STMicroelectronics

Specifications of EVALED7706

• Current - Output / Channel: 30mA
• Outputs And Type: 6, Non-Isolated
• Voltage - Output: 36 V
• Features: Dimmable, Extra 5V Output
• Voltage - Input: 4.5 ~ 36 V
• Utilized Ic / Part: LED7706
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 497-6445

Operation description
5.2.2
20/46
PWM dimming
The brightness control of the LEDs is performed by a pulse-width modulation of the rows
current. When a PWM signal is applied to the DIM pin, the current generators are turned on
and off mirroring the DIM pin behavior. Actually, the minimum dimming duty-cycle depends
on the dimming frequency.
The real limit to the PWM dimming is the minimum on-time that can be managed for the
current generators; this minimum on-time is approximately 500 ns.
Thus, the minimum dimming duty-cycle depends on the dimming frequency according to the
following formula:
Equation 11
For example, at a dimming frequency of 20 kHz, 1% of dimming duty-cycle can be
managed.
During the off-phase of the PWM signal the boost converter is paused and the current
generators are turned off. The output voltage can be considered almost constant because of
the relatively slow discharge of the output capacitor. During the start-up sequence (see
Section 5.1.3 on page 13
regardless of the applied dimming signal.
Figure 14. PWM dimming waveforms
) the dimming duty-cycle is forced to 100% to detect floating rows
D
DIM
,
min
=
500
ns
⋅
f
DIM
LED7706