ISL6557A 데이터 시트보기 (PDF) - Renesas Electronics
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ISL6557A Datasheet PDF : 18 Pages
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ISL6557A
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 ISL6557A uses a digital to analog converter (DAC) to gen-
erate 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 20A pull up to 2.5V for use with open-drain out-
puts. 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 differ-
ential remote-sense amplifier usually gets connected to the
error amplifier as shown in Figure 7. The remote-sense ampli-
fier eliminates voltage differences between local and remote
ground to provide a more accurate means of sensing output
voltage.
EXTERNAL CIRCUIT
RC
CC
COMP
ISL6557A INTERNAL CIRCUIT
RFB
+
VDROOP
-
FB
IOUT
VDIFF
ERROR AMPLIFIER
-
IAVG
+
VCOMP
REFERENCE
VOLTAGE
VOUT
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 ISL6557A 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
0.800
1
1
1
0
1
0.825
1
1
1
0
0
0.850
1
1
0
1
1
0.875
1
1
0
1
0
0.900
1
1
0
0
1
0.925
1
1
0
0
0
0.950
1
0
1
1
1
0.975
1
0
1
1
0
1.000
1
0
1
0
1
1.025
1
0
1
0
0
1.050
1
0
0
1
1
1.075
1
0
0
1
0
1.100
1
0
0
0
1
1.125
1
0
0
0
0
1.150
0
1
1
1
1
1.175
0
1
1
1
0
1.200
0
1
1
0
1
1.225
0
1
1
0
0
1.250
0
1
0
1
1
1.275
0
1
0
1
0
1.300
0
1
0
0
1
1.325
0
1
0
0
0
1.350
0
0
1
1
1
1.375
0
0
1
1
0
1.400
0
0
1
0
1
1.425
0
0
1
0
0
1.450
0
0
0
1
1
1.475
0
0
0
1
0
1.500
0
0
0
0
1
1.525
0
0
0
0
0
1.550
FN9068 Rev 3.00
July 2004
Page 9 of 18
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