ISL8120IR Datasheet, PDF (31/33 Pages) Intersil Corporation – Full Traceability Through Assembly and Test

ISL8120IR
loading, Channel 1 might drop faster than Channel 2. To solve
this race condition, Channel 2 can either power up from
Channel 1 or bridge the Channel 1 with a high current
Schottky diode. If the system requires to shutdown both
channels when either has a fault, tying EN/FF1 and EN/FF2
will do the job. In DDR mode, Channel 1 delays 60° over
Channel 2.
In Dual mode, depending upon the resistor divider level of
REFIN from VCC, the ISL8120IRZEC operates as a dual
PWM controller for two independent regulators with a phase
shift as shown in Table 2. The phase shift is latched as VCC
raises above POR and cannot be changed on-the-fly.
TABLE 2.
DECODING PHASE for CHANNEL REQUIRED
MODE REFIN RANGE 2 WRT CHANNEL 1
REFIN
DDR <29% of VCC
-60°
0.6V
Dual 29% to 45% of
0°
VCC
37% VCC
Dual 45% to 62% of
90°
VCC
53% VCC
Dual 62% to VCC
180°
VCC
V_{OS_DA} should set to zero when the differential amplifier is
in the loop, the differential amplifier’s input impedance
(R_DIF) is typically 500kΩ with a tolerance of 20% (R_DIF%)
and can be neglected when R_OS is less than 100Ω. To set a
precision setpoint, R_OS can be scaled by two paralleled
resistors.
VDDQ
PHASE-SHIFTED
CLOCK
k*R
CLKOUT/REFIN
VCC VSEN2-
ISL8120IRZEC
STATE
MACHINE
R
k
=
V_-----D_-----D_-----Q_---
0.6 V
–
1
INTERNAL SS
700mV
0.6V
FB2
E/A2
FIGURE 23. SIMPLIFIED DDR IMPLEMENTAION
Internal Reference and System Accuracy
The internal reference is set to 0.6V. Including bandgap
variation and offset of differential and error amplifiers, it has
an accuracy of 0.9% over industrial temperature range.
While the remote sense is not used, its offset (V_{OS_DA})
should be included in the tolerance calculation. Equations 9
and 10 show the worst case of system accuracy calculation.
VOUT (LOCAL)
VSENSE- (REMOTE)
10Ω
VSENSE+ (REMOTE)
GND (LOCAL)
10Ω
C_SEN
R_OS
R_FB
VCC
VSEN-
VSEN+
Z_FB
VMON
Z_COMP
FB
COMP
PGOOD
700mV
GAIN=1
V_REF
OV/UV
COMP
ERROR AMP
PGOOD
FIGURE 24. SIMPLIFIED REMOTE SENSING IMPLEMENTATION
31
FN6763.2
November 11, 2011