ISL6557 Datasheet, PDF (9/17 Pages) Intersil Corporation – Multi-Phase PWM Controller for Core-Voltage Regulation

ISL6557
indefinitely as shown in Figure 6 as long as the controller is
enabled or until the overcurrent condition resolves.
OUTPUT CURRENT, 20A/DIV
0A
OUTPUT VOLTAGE,
500mV/DIV
0V
5ms/DIV
FIGURE 6. OVERCURRENT BEHAVIOR IN HICCUP MODE
VOLTAGE REGULATION
The ISL6557 uses a digital to analog converter (DAC) to
generate a reference voltage based on the logic signals at
pins VID4 to VID0. The DAC decodes the a 5-bit logic signal
(VID) into one of the discrete voltages shown in Table 1.
Each VID input offers a 20µA pull-up to 2.5V for use with
open-drain outputs. External pull-up resistors or active-high
output stages can augment the pull-up current sources, but
a slight accuracy error can occur if they are pulled above
2.9V.
._{The DAC-selected reference voltage is connected to the}
non-inverting input of the error amplifier, and the output of
the differential remote-sense amplifier usually gets
connected to the error amplifier as shown in Figure 7. The
remote-sense amplifier eliminates voltage differences
between local and remote ground to provide a more
accurate means of sensing outputvoltage.
EXTERNAL CIRCUIT
R_C
C_C
COMP
FB
R_FB
+
V_DROOP
-
IOUT
VDIFF
ISL6557 INTERNAL CIRCUIT
ERROR AMPLIFIER
-
I_AVG
+
V_COMP
REFERENCE
VOLTAGE
V_OUT
VSEN
+
REMOTE
GROUND
RGND
-
DIFFERENTIAL
REMOTE-SENSE
AMPLIFIER
FIGURE 7. OUTPUT VOLTAGE AND LOAD-LINE
REGULATION
The integrating compensation network shown in Figure 7
assures that the steady-state error in the output voltage is
limited to the error in the reference voltage (output of the
DAC) plus offset errors in the remote-sense and error
amplifiers. Intersil specifies the guaranteed tolerance of the
ISL6557 and all Intersil controllers to include all variations in
the amplifiers and reference so that the output voltage
remains within the specified system tolerance.
TABLE 1. VOLTAGE IDENTIFICATION CODES
VID4
VID3
VID2
VID1
VID0 VDAC
1
1
1
1
1
Off
1
1
1
1
0
1.100
1
1
1
0
1
1.125
1
1
1
0
0
1.150
1
1
0
1
1
1.175
1
1
0
1
0
1.200
1
1
0
0
1
1.225
1
1
0
0
0
1.250
1
0
1
1
1
1.275
1
0
1
1
0
1.300
1
0
1
0
1
1.325
1
0
1
0
0
1.350
1
0
0
1
1
1.375
1
0
0
1
0
1.400
1
0
0
0
1
1.425
1
0
0
0
0
1.450
0
1
1
1
1
1.475
0
1
1
1
0
1.500
0
1
1
0
1
1.525
0
1
1
0
0
1.550
0
1
0
1
1
1.575
0
1
0
1
0
1.600
0
1
0
0
1
1.625
0
1
0
0
0
1.650
0
0
1
1
1
1.675
0
0
1
1
0
1.700
0
0
1
0
1
1.725
0
0
1
0
0
1.750
0
0
0
1
1
1.775
0
0
0
1
0
1.800
0
0
0
0
1
1.825
0
0
0
0
0
1.850
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