SC5010H View Datasheet(PDF) - Semtech Corporation
Part Name
Description
MFG CO.
SC5010H
Semtech Corporation
'SC5010H' PDF : 36 Pages View PDF
SC5010H
Applications Information (continued)
a micro-controller sets a register or counter that varies the
pulse width on a GPIO pin. The SC5010H allows dimming
over a wide frequency range (100Hz-30kHz) in order to
allow compatibility with a wide range of devices. This
includes the newest dimming strategies that avoid the
audio band by using high frequency PWM dimming. In
this manner, a wide range of illumination can be gener-
ated while keeping the instantaneous LED current at its
peak value for high efficiency and color temperature. The
SC5010H provides 1000:1 dimming range at 1kHz PWM
frequency. The LED current sinks turn on /off very rapidly
(<25ns, typical). This allows wide dimming ratio. An addi-
tional advantage of PWM dimming comes to customers
who prefer to avoid in-rush currents when filling the boost
output capacitor. Apply the PWMI signal to the device at
10% duty for a millisecond or two, and in-rush current is
reduced. This dimming time will vary based on the number
of LEDs and the size of the output capacitor. This can be
easily determined during testing and programmed into
the micro-controller firmware.
Mode 2 — Indirect Control
This is the default mode for LED PWM dimming in SC5010H.
In this mode, the input signal applied on PWMI pin is passed
through a duty cycle extractor block. The extractor mea-
sures the duty cycle of the PWMI input, and depending on
the value of FAST_FREQ, the duty cycle is converted to a 9-
bit value (FAST_FREQ = 1) or a 10-bit value (FAST_FREQ = 0).
This value is then passed to the PWM generator block as
shown in the Figure 1 below.
The LED PWM dimming frequency is set via the FREQ reg-
ister (address 0x05) and the FAST_FREQ bit.
With FAST_FREQ = 0, low dimming frequency option is
selected and the PWM dimming frequency will be accord-
ing to the following equation.
PWM Dimming Frequency
10MHz
1024 u [FREQ[7 : 0] 1]
10kHz(max)
With FAST_FREQ = 1, high dimming frequency option is
selected and the PWM dimming frequency is shown by
the following equation.
PWM Dimming Frequency
10MHz
512 u [FREQ[7 : 0] 1]
20kHz(max)
The default option is FAST_FREQ = 1. This gives 9-bit duty
cycle resolution and up to 20kHz dimming frequency
Extracted duty
LED Frequency and PhaseShifter Block
cycle from
PW MI Input
PWMI
Duty Cycle
Extractor
10
0
10
PWM
PWMI
1
Phase Shifting
0
Input
G enerator
(45º)
10
EN
1
8
1
PW M_ps[8:1]
All bits identical
when phase
shifting disabled
8
Softstart
PW M [8:1]
8
D[9:0] Bits
INT_DUTY Bit
FREQ Bits
FastFreq Bit
PH_SHIFT Bit
INT_PW M Bit
I2C Interface
Figure 1— LED PWM Dimming Control
18
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