ISL85033EVAL2Z Datasheet, PDF (1/2 Pages) Intersil Corporation – Wide VIN Dual Standard Buck Regulator With 3A/3A Output Current - Short Form

Application Note 1585
Author: Paul Orfanu
ISL85033EVAL2Z (Small Form) Wide VIN Dual
Standard Buck Regulator With 3A/3A Output
Current - Short Form
Description
The ISL85033EVAL2Z kit demonstrates performance of
the ISL85033 switching regulator IC. An input range of
4.5V to 28V and 3A output per channel (connect in
parallel to 6A) allows the ISL85033 to meet a wide
variety of POL requirements.
The ISL85033 is offered in a 4mmx4mm 28 Ld TQFN
package with 1mm maximum height. The complete
converter occupies 6.25cm² area.
100
90
80
12V_OUT 1MHz
9V_OUT 1MHz
70
5V_OUT 500kHz
60
3.3V_OUT 500kHz
50
1.8V_OUT 300kHz
40
0.0
0.5
1.0
1.5
2.0
2.5
3.0
OUTPUT LOAD (A)
FIGURE 1. EFFICIENCY vs LOAD, T_A = +25°C,
V_IN = 28V
1.629’
FIGURE 2. ISL85033EVAL2Z TOP LAYER COMPONENTS
Key Features
• Wide Input Voltage Range from 4.5V to 28V
• Adjustable Output Voltage with Continuous Output
Current up to 3A per channel
• 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
Quick Setup Guide
1. Ensure correct board connection to the supply (“+”
to VIN1 and “-” to GND2) and loads prior to applying
power, then turn on the power supply.
2. Verify the output voltage is 5V for V_OUT1 and 3.3V
for V_OUT2.
Frequency Control
ISL85033 has an FS pin that controls the frequency of
operation. Programmable frequency allows for
optimization between efficiency and external
component size. ISL85033EVAL2Z has the switching
frequency set to 500kHz (FS is tied to VCC).
SYNC Control
The ISL85033 has a SI pin for external synchronization.
Default board configuration has R8 = 0 to GND, which
defaults to the internally selected switching frequency.
Removing R8 allows the synchronization to be external
between 600kHz to 4MHz. Do not leave this pin floating.
Output Voltage Selection
ISL85033EVAL2Z board has V_OUT1 set to 5V and V_OUT2 set
to 3.3V. The output voltage programming resistor, R₃ (R₁₀
respectively), will depend on the value chosen for the
feedback resistor, R₂ (R₁₂ respectively), and the desired
output voltage, V_OUT, see Equation 1. The value for R₂ (R₁₂
respectively) is typically between 1k and 10k.
R₃ = (V_OUT1 – V_FB ) • R₂ ⁄ 0.8
R₁₀ = (V_OUT2 – V_FB ) • R₁₂ ⁄ 0.8
(EQ. 1)
Please note that if V_OUT is less than 2.5V, switching
frequency and compensation must be changed for
300kHz operation due to minimum on-time limitation.
Please refer to data sheet FN6676 for further information.
November 29, 2010
1
AN1585.1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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