ISL97673IRZ-TK Intersil, ISL97673IRZ-TK Datasheet - Page 24

• Manufacturer Part Number: ISL97673IRZ-TK
• Description: IC LED DVR PWM CTRL 6CH 20QFN
• Manufacturer: Intersil

Specifications of ISL97673IRZ-TK

• 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
• Voltage - Output: *
• 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

Phase Shift Control Register (0x0A)
The Phase Shift Control register is used to set phase
delay between each channels. When bit 7 is set high, the
phase delay is set by the number of channels enabled
and the PWM frequency. The delay time is defined by the
Equation 13:
where N is the number of channels enabled, and t
the period of the PWM cycle. When bit 7 is set low, the
phase delay is set by bits 6 to 0 and the PWM frequency.
The delay time is defined by Equation 14:
where PS is an integer from 0 to 127, and t
period of the PWM cycle. By default, all the register bits
are set low, which sets zero delay between each channel.
Note that the user should not program the register to
give more than one period of the PWM cycle delay
between the first and last enabled channels.
Components Selections
According to the inductor Voltage-Second Balance
principle, the change of inductor current during the
switching regulator On time is equal to the change of
inductor current during the switching regulator Off time.
Since the voltage across an inductor is:
and ΔI
where D is the switching duty cycle defined by the turn-on
time over the switching period. V
forward voltage that can be neglected for approximation.
t
t
V
(
DELAY
DELAY
V
L
Bit 7 (R/W)
REGISTER 0x0A
I
–
EQUAL
BIT ASSIGNMENT
=
PHASE
0 ) L ⁄
PhaseShift[6..0]
L
L
×
EqualPhase
=
=
@ On = ΔI
ΔI
(
(
×
t
PS
L
FPWM
D
⁄
Δt
×
<
t
6 0
S
,
=
⁄
Bit 6 (R/W)
N
PHASE-
SHIFT6
>
(
L
)
V
xt
O
@ Off, therefore:
PHASE SHIFT CONTROL REGISTER
FPWM
–
V
FIGURE 36. DESCRIPTIONS OF PHASE SHIFT CONTROL REGISTER
D
24
–
Note that user must not specify a value that gives >360° shift between first and last
⁄
V
(
Controls phase shift mode - When 0, phase shift is defined by PhaseShift<6:0>.
255
I
)
⁄
When 1, phase shift is 360/N (where N is the number of channels enabled).
L
Bit 5 (R/W)
)
)
×
PHASE-
SHIFT5
D
1 (
is Schottky diode
–
7-bit Phase shift setting - phase shift between each channel is
D )
In direct PWM modes, phase shift between each channel is
×
t
S
FPWM
Bit 4 (R/W)
PHASE-
SHIFT4
(EQ. 13)
(EQ. 14)
(EQ. 16)
is the
(EQ. 15)
FPWM
PhaseShift<6:0>/(255*PWMFreq)
BIT FIELD DEFINITIONS
PhaseShift<6:0>/12.8MHz
ISL97673
is
channels.
Bit 3 (R/W)
Rearranging the terms without accounting for V
the boost ratio and duty cycle respectively as:
Input Capacitor
Switching regulators require input capacitors to deliver
peak charging current and to reduce the impedance of
the input supply. This reduces interaction between the
regulator and input supply, thereby improving system
stability. The high switching frequency of the loop causes
almost all ripple current to flow in the input capacitor,
which must be rated accordingly.
A capacitor with low internal series resistance should be
chosen to minimize heating effects and improve system
efficiency, such as X5R or X7R ceramic capacitors, which
offer small size and a lower value of temperature and
voltage coefficient compared to other ceramic capacitors.
In Boost mode, input current flows continuously into the
inductor; AC ripple component is only proportional to the
rate of the inductor charging, thus, smaller value input
capacitors may be used. It is recommended that an input
capacitor of at least 10µF be used. Ensure the voltage
rating of the input capacitor is suitable to handle the full
supply range.
Inductor
The selection of the inductor should be based on its
maximum current (I
dissipation (DCR), EMI susceptibility (shielded vs
unshielded), and size. Inductor type and value influence
many key parameters, including ripple current, current
limit, efficiency, transient performance and stability.
The inductor’s maximum current capability must be
adequate enough to handle the peak current at the worst
case condition. If an inductor core is chosen with too low
V
D
PHASE-
SHIFT3
O
=
⁄
V
(
V
I
=
O
1
–
⁄
V
(
1 D
I
) V
–
⁄
O
Bit 2 (R/W)
)
PHASE-
SHIFT2
SAT
) characteristics, power
Bit 1 (R/W)
PHASE-
SHIFT1
Bit 0 (R/W)
PHASE-
SHIFT0
June 24, 2010
D
(EQ. 17)
(EQ. 18)
gives
FN7633.0