ISL6521EVAL1 Intersil, ISL6521EVAL1 Datasheet - Page 2

• Manufacturer Part Number: ISL6521EVAL1
• Description: EVALUATION BOARD 1 ISL6521
• Manufacturer: Intersil

Specifications of ISL6521EVAL1

• Main Purpose: DC/DC, Step Down with LDO
• Outputs And Type: 4, Non-Isolated
• Power - Output: 13.5W
• Voltage - Output: 1.5V, 2.5V, 3.3V, 1.8V
• Current - Output: 5A, 1A, 1A, 120mA
• Voltage - Input: 4.5 ~ 5.5V
• Regulator Topology: Buck
• Frequency - Switching: 300kHz
• Board Type: Fully Populated
• Utilized Ic / Part: ISL6521
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

ISL6521EVAL1 Performance
Enabling the Controller
Once the bias voltage applied to the PWM controller reaches
the rising Power-On Reset (POR) threshold, the ISL6521
initiates a soft-start interval. The point at which the ISL6521
reaches the rising POR threshold is indicated as Soft-start
Begins in Figure 3. After a short delay, the four outputs
begin ramping to the output levels set by external resistor
dividers to the FB pins. The controlled voltage ramp of all
four outputs charges the output capacitors of each output
slowly and softens the initial current drawn from the bias
supply. Reducing the soft-start interval lasts about 3ms and
ends just after all four output reach their programmed output
levels. The point soft-start ends is indicated as Soft-start
Ends in Figure 3.
Load
Load
FIGURE 2. EXTERNAL POWER SUPPLY AND LOAD
Soft-start Begins
CONNECTIONS
FIGURE 3. SOFT-START INTERVAL
VCC, 2V/div
Power
Indicator
Soft-start Ends
1ms/div
2
Input Power
Supply
VOUT2, 1V/div
VOUT3, 1V/div
VOUT4, 1V/div
VOUT1, 1V/div
Application Note 1247
Load
Load
Output Voltage Ripple
The evaluation platform is designed to meet a core voltage
ripple specification of 20mV. Board performance is shown in
Figure 4, under room temperature conditions and light
loading. The output voltage ripple measures less than 18mV.
Adjustment of output voltage ripple is addressed in the
Adapting Circuit Performance section.
Protection Features
The ISL6521 features overcurrent protection on the PWM
controller. The linear controllers feature undervoltage
protection which doubles as overcurrent protection.
The PWM controller uses the upper MOSFET’s on-resistance,
r
current level is then compared internally to the overcurrent trip
point set externally. The overcurrent protection monitors these
conditions on a cycle by cycle basis. When the overcurrent
trip level is exceeded, the PWM controller removes gate drive
to the MOSFETs. The ISL6521 then enters a wait period
equivalent to three soft-start intervals. A soft-start interval
follows and if the overcurrent condition remains, the controller
will trip off again. This results in the hiccup mode response to
a sustained short shown in Figure 5. The PWM controller exits
this mode once the output voltage soft-starts successfully or
bias is removed from the controller.
DS(on)
FIGURE 5. HICCUP MODE OVERCURRENT PROTECTION
, to monitor the current flow through the device. This
VOUT1, 20mV/div
PHASE, 5V/div
FIGURE 4. CORE VOLTAGE RIPPLE (VOUT1)
OC Event Occurs
20ms/div
5µs/div
IOUT1, 5A/div
VOUT1, 0.5V/div
July 10, 2006
AN1247.0