ISL78171 Datasheet, PDF (27/29 Pages) Intersil Corporation – 6-Channel, 50mA Automotive LED Driver with Ultra-high Dimming Ratio and Phase Shift Control

ISL78171
VIN = 3V~21V
ISL78171
1 FAULT
2 VIN
4 _VDC
LX 20
OVP 16
PGND 19
7 SMBCLK/SCL
6 SMBDAT/SDA
5 PWM
3 EN
CH0 10
CH1 11
CH2 12
CH3 13
17 _RSET
CH4 14
8 FPWM
CH5 15
9 AGND
COMP 18
26.5V, 6 x 50mA*
*VIN > 12V
FIGURE 43. SINGLE SUPPLY 3V OPERATION
VIN = 2.7~26.5V
Q1 (OPTIONAL)
VBIAS = 5V~12V
ISL78171
1 FAULT
2 VIN
4 _VDC
LX 20
OVP 16
PGND 19
7 SMBCLK/SCL
6 SMBDAT/SDA
5 PWM
3 EN
CH0 10
CH1 11
CH2 12
CH3 13
17 _RSET
CH4 14
8 FPWM
CH5 15
9 AGND
COMP 18
40V, 6 x 50mA*
*VIN > 12V
16-Bit Dimming
The SMBus/I²C controlled PWM and DC dimming can be
combined to effectively provide 16 bits of dimming capability,
which can be valuable for automotive and avionics display
applications.
Field Sequential RGB LED Backlighting
The ISL78171 allows to turn each channel ON and OFF
independently. In field sequential RGB LED application, it is
possible to have different DC current and PWM duty cycle for
different channels as long as only one channel is active at a time.
This is achieved by continuously setting a new DC current and/or
PWM duty cycle each time a channel is turned ON. ISL78171
does not allow to have different DC currents or PWM duty cycles
for channels that are ON at the same time.
Compensation
The ISL78171 incorporates a transconductance amplifier in its
feedback path to allow the user to optimize boost stability and
transient response. The ISL78171 uses current mode control
architecture, which has a fast current sense loop and a slow
voltage feedback loop. The fast current feedback loop does not
require any compensation, but for stable operation, the slow
voltage loop must be compensated. The compensation is a
series of Rc, Cc1 network from COMP pin to ground, with an
optional Cc2 capacitor connected between the COMP pin and
ground. The Rc sets the high-frequency integrator gain for fast
transient response, and the Cc1 sets the integrator zero to
ensure loop stability. For most applications, the component
values in Figure 45 can be used: Rc is 10kΩ and Cc1 is 3.3nF.
Depending upon the PCB layout, for stability, a Cc2 of 390pF may
be needed to create a pole to cancel the output capacitor ESR’s
zero effect.
Rc 10k
Cc1
3.3nF
Cc2
390pF
COMP
FIGURE 44. DUAL SUPPLIES 2.7V OPERATION
FIGURE 45. COMPENSATION CIRCUIT
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FN8602.0
June 15, 2015