ISL6529CR Intersil, ISL6529CR Datasheet - Page 8

• Manufacturer Part Number: ISL6529CR
• Description: IC CTRLR PWM DUAL REG 16-QFN
• Manufacturer: Intersil
• Type: Step-Down (Buck)r

Specifications of ISL6529CR

• Internal Switch(s): No
• Synchronous Rectifier: Yes
• Number Of Outputs: 2
• Voltage - Output: 0.5 ~ 4.5 V
• Frequency - Switching: 600kHz
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 16-VQFN Exposed Pad, 16-HVQFN, 16-SQFN, 16-DHVQFN
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Current - Output: -
• Voltage - Input: -
• Power - Output: -

Undervoltage Protection
The FB and FB2 pins are monitored during converter
operation by two separate undervoltage (UV) comparators. If
the FB voltage drops below 51.5% of the reference voltage
(0.41V), a fault signal is generated. The internal fault logic
shuts down both regulators simultaneously when the fault
signal triggers a restart.
Figure 3 illustrates the protection feature responding to a UV
event on V
51.5% 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.
FIGURE 2. TOP SCOPE TRACES ARE VOLTAGE RAMP AND
OUT1
CAPACITOR CURRENT. LOWER TRACES ARE
TIME AND VOLTAGE EXPANSION OF UPPER
SCOPE TRACES.
. At time t0, VOUT1 has dropped below
CAPACITOR CURRENT
CAPACITOR CURRENT
8
1.5V OUTPUT
1.5V OUTPUT
ISL6529, ISL6529A
Had the cause of the UV still been present after the delay
interval, the UV protection circuitry becomes active
approximately 875ms into the soft-start interval. A fault
signal could then be generated and the outputs once again
shut down. 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
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 4).
0V
0V
FIGURE 3. UNDERVOLTAGE PROTECTION RESPONSE
(0.5V/DIV)
t0
INTERNAL SOFT-START FUNCTION
V
OUT2
DELAY INTERVAL
V
DELAY INTERVAL
t1
OUT1
IN
(2.5V)
(1.5V)
(i.e. +3.3V) and the internal
V
TIME
OUT2
t2
(2.5V)
t3
April 12, 2005
t4
FN9070.5