ISL97671IRZ-T Intersil, ISL97671IRZ-T Datasheet - Page 12

• Manufacturer Part Number: ISL97671IRZ-T
• Description: IC LED DVR PWM CTRL 6CH 20QFN
• Manufacturer: Intersil

Specifications of ISL97671IRZ-T

• Topology: PWM, Step-Up (Boost)
• Number Of Outputs: 6
• Internal Driver: Yes
• Type - Primary: Automotive, Backlight
• Type - Secondary: RGB, White LED
• Frequency: 600kHz ~ 1.2MHz
• Voltage - Supply: 4.5 V ~ 26.5 V
• Mounting Type: Surface Mount
• Package / Case: 20-VFQFN Exposed Pad
• Operating Temperature: -40°C ~ 85°C
• Current - Output / Channel: 40mA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Output: -

LILED ave
Equations 2 and 3. The source of the PWM signal can be
described as follows:
The default PWM dimming is in DPST mode. In all three
methods, the average LED current of each channel is
controlled by I
shown in Equation 6:
Method 1 (Internal Mode, SMBus/I
PWM)
The average LED current of each channel is controlled
by the internally generated PWM signal, as shown in
Equation 7:
where BRT is the PWM brightness level programmed in
the Register 0x00. BRT ranges from 0 to 255 in decimal
and defaults to 255 (0xFF). BRT = 0 disconnects all
channels.
To use only the SMBus/I
control, users need to set Register 0x01 to 0x05 with
EN/PWM in logic high.
The SMBus/I
a resistor at the FPWM pin, which will be described in
“PWM Dimming Frequency Adjustment” on page 12.
Method 2 (External Mode)
The average LED current of each channel can also be
controlled by an external PWM signal, as shown in
Equation 8:
The PWM dimming frequency can be set (see PWM
Dimming Frequency Adjustment section) or applied up to
30kHz with duty cycles from 0.4% to 100%. The PWM
dimming off time cannot be longer than 28ms or else the
driver will enter shutdown.
To use externally applied PWM signal only for brightness
control, users need to set Register 0x01 to 0x03.
Method 3 (DPST Mode)
The average LED current of each channel can also be
controlled by the product of the SMBus/I
PWM and the external PWM signals as:
I
I
I
1. Internally generated 256 step duty cycle
2. External signal from PWM.
3. DPST mode. Internally generated signal with a
LED ave
LED ave
LED ave
programmed through the SMBus/I
duty cycle defined by the product of the external
PWM and SMBus/I
internal setting frequency.
(
(
(
(
)
)
)
)
=
=
=
=
I
I
I
I
LED
LED
LED
LED
2
C controlled PWM frequency is adjusted by
LED
xPWM
×
×
×
PWM
(
PWMI
BRT 255
and the PWM duty cycle in percent, as
DPST
⁄
2
C programmed PWM at the
2
C controlled PWM brightness
12
)
2
C.
2
2
C controlled
C controlled
(EQ. 6)
(EQ. 7)
(EQ. 8)
(EQ. 9)
ISL97671
Where:
Therefore:
Where BRT is the value held in Register 0x00 (default
setting 0xFF) controlled by SMBus/I
duty cycle of the incoming PWM signal. In this way, the
users can change the PWM current in ratiometric manner
to achieve DPST compliance backlight dimming.
To use the DPST mode, users need to set Register 0x01
to 0x01 with external PWM signal.
The DPST mode PWM frequency is adjusted by a
resistor at the FPWM pin which will be described in
“PWM Dimming Frequency Adjustment” on page 12.
For example, if the SMBus/I
80% dimming at 200Hz (see Equation 12) and the
external PWM duty cycle is 60% dimming at 1kHz, the
resultant PWM duty cycle is 48% dimming at 200Hz.
PWM Dimming Frequency Adjustment
The PWM dimming frequency is set by an external
resistor at the FPWM pin as:
where F
and R
The PWM dimming frequency can be set or applied up to
30kHz with duty cycle from 0.4% to 100%.
Phase Shift Control
The ISL97671 is capable of delaying the phase of each
current source to minimize load transients. By default,
phase shifting is disabled as shown in Figure 21 where
the channels PWM currents are switching uniformly. The
duty cycles can be controlled by the data in PWM
Brightness Control Register via the SMBus/I
an external PWM signal with the frequency set by the
RFPWM, or by an external PWM signal with the frequency
set by the incoming signal.
PWM
I
F
LED ave
PWM
(
DPST
FPWM
=
)
PWM
----------------------- -
RFPWM
6.66
=
=
I
is the setting resistor.
LED
×10
BRT 255
is the desirable PWM dimming frequency
7
×
⁄
BRT 255
×
⁄
PWMI
×
PWMI
2
C controlled PWM duty is
2
C and PWM is the
2
C interface,
June 24, 2010
(EQ. 10)
(EQ. 11)
(EQ. 12)
FN7631.0