ISL6528 Intersil Corporation, ISL6528 Datasheet - Page 6

• Manufacturer Part Number: ISL6528
• Description: Dual Regulator - Standard Buck PWM and Linear Power Controller
• Manufacturer: Intersil Corporation

shuts down both regulators simultaneously when the fault
signal triggers a restart.
Figure 2 illustrates the protection feature responding to an
UV event on V
52.5% of the nominal output voltage. Both outputs are
quickly shut down and the internal soft-start function begins
producing soft-start ramps. The delay interval, T0 to T3,
seen by the output is equivalent to three soft-start cycles.
After a short delay interval of 10.5ms, the fourth internal soft-
start cycle initiates a normal soft-start ramp of the output, at
time T3. Both outputs are brought back into regulation by
time T4, as long as the UV event has cleared.
Had the cause of the UV still been present after the delay
interval, the UV protection circuitry becomes active
approximately 875 µ s into the soft-start interval. A fault signal
could then be generated and the outputs once again
shutdown. The resulting hiccup mode style of protection
would continue to repeat indefinitely.
Output Voltage Selection
The output voltage of the PWM converter can be
programmed to any level between V
internal reference, 0.8V. An external resistor divider is used
to scale the output voltage relative to the reference voltage
and feed it back to the inverting input of the error amplifier,
see Figure 3. However, since the value of R1 affects the
values of the rest of the compensation components, it is
advisable to keep its value less than 5k Ω . Depending on the
0V
0V
(1V/DIV)
(0.5V/DIV)
FIGURE 1. SOFT-START INTERVAL
OUT1
T0
. At time T0, VOUT1 has dropped below
T1
+3.3V (UPPER FET DRAIN)
TIME
+5V (VCC)
6
T2
V
V
OUT1
OUT2
IN
(i.e. +3.3V) and the
(1.5V)
(2.5V)
ISL6528
value chosen for R1, R4 can be calculated based on the
following equation:
If the output voltage desired is 0.8V, simply route VOUT1
back to the FB pin through R1, but do not populate R4.
0V
0V
FIGURE 3. OUTPUT VOLTAGE SELECTION OF THE PWM
C
V
FIGURE 2. UNDERVOLTAGE PROTECTION RESPONSE
OUT1
OUT1
(0.5V/DIV)
T0
+
R3
V
OUT2
V
OUT1
Internal Soft-Start Function
L
C3
R1
OUT
(2.5V)
T1
Delay Interval
R4
Delay Interval
R4
(1.5V)
C4
=
------------------------------------- -
V
D2
R2
OUT1
R1 0.8V
Q1
V
+3.3V
TIME
C2
OUT2
T2
×
C1
D1
–
(2.5V)
0.8V
UGATE
BOOT
COMP
FB
T3
(EQ. 1)
ISL6528
VCC
+5V
T4