ISL85033DUALEVAL1Z Datasheet, PDF (1/9 Pages) Intersil Corporation – Wide VIN Dual Standard Buck Regulator With 3A/3A Output Current

Application Note 1574
Author: Paul Orfanu
ISL85033DUALEVAL1Z Wide VIN Dual Standard
Buck Regulator With 3A/3A Output Current
Description
The ISL85033DUALEVAL1Z kit is intended for use by
individuals with requirements for Point-of-Load
applications sourcing from 4.5V to 28V. The
ISL85033DUALEVAL1Z evaluation board is used to
demonstrate the performance of the ISL85033 wide VIN
dual standard buck regulator with 3A/3A output
current converter.
The ISL85033 is offered in a 4mmx4mm 28 Ld TQFN
package with 1mm maximum height. The complete
converter occupies 6.25cm² area.
Key Features
• Wide Input Voltage Range from 4.5V to 28V
• Adjustable Output Voltage with Continuous Output
Current up to 3A
• Current Mode Control
• Adjustable Switching Frequency from 300kHz to 2MHz
• Independent Power-Good Detection
• Selectable In-Phase or Out-of-Phase PWMs Switching
Operation
• Independent, Sequential, Ratiometric or Absolute
Tracking Between Outputs
• Internal 2ms Soft-start Time
• Overcurrent and Hiccup Mode Short Circuit
Protection, Thermal Overload Protection, UVLO
• Boot Undervoltage Detection
• Channels are Out-of-phase, Reducing Voltage Ripple
and Component Size
Recommended Equipment
The following materials are recommended to perform
testing:
• 0V to 30V Power Supply with at least 7A source
current capability or 5V battery
• Electronic Loads capable of sinking current up to 7A
• Digital Multimeters (DMMs)
• 100MHz quad-trace oscilloscope
• Signal generator
Quick Setup Guide
1. Ensure that the circuit is correctly connected to the
supply and loads prior to applying any power.
2. Connect the bias supply to VIN1, the plus terminal
to VIN1 and the negative return to GND2.
3. Verify that the position is ON for S1 and S2.
4. Turn on the power supply.
5. Verify the output voltage is 5V for V_OUT1 and 3.3V
for V_OUT2.
Evaluating the Other Output Voltage
The ISL85033DUALEVAL1Z kit outputs are preset to 5V
for V_OUT1 and 3.3V for V_OUT2; however, output voltages
can be adjusted from 0.8V to 5V. The output voltage
programming resistor, R3 (or R14 in Channel 2), will
depend on the desired output voltage of the regulator
and the value for the feedback resistor R2 (R16
respectively), as shown in Equation 1.
R3 = (V_OUT1 – V_FB ) • R2 ⁄ V_FB
(EQ. 1)
R14 = (V_OUT2 – V_FB ) • R16 ⁄ V_FB
If the output voltage desired is 0.8V, then R3 (R14
respectively) is shorted. The value for R2 (R16
respectively) is typically between 1k and 10k. Please
note that if VOUT is less than 2.5V, the switching
frequency and compensation must be changed for
300kHz operation due to minimum on-time limitation.
Please refer to the data sheet for further information
(FN6676).
Frequency Control
ISL85033 has an FS pin that controls the frequency of
operation. Programmable frequency allows for
optimization between efficiency and external
component size. Default switching frequency is 500kHz
when FS is tied to VCC (R9 = 0). By removing R9 and
connecting R10 to ground, the switching frequency
could be changed from 300kHz (R10 = 383k) to 2MHz
(R10 = 40.2k). Please refer to the data sheet
(FN6676) for calculating the value of R10. Do not leave
this pin floating.
November 29, 2010
AN1574.2
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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