ISL85403

2.5A Regulator with Integrated High-Side MOSFET for Synchronous Buck or Boost Buck Converter

OVERVIEW

The ISL85403 is a 40V, 2.5A synchronous buck or boost buck controller with a high-side MOSFET and low-side driver integrated. In buck mode, the ISL85403 supports a wide input range of 3V to 40V. In boost-buck mode, the input range can be extended down to 2.5V and output regulation can be maintained when VIN drops below VOUT , enabling sensitive electronics to remain on in low input voltage conditions.

The ISL85403 has a flexible selection of operation modes of forced PWM mode and PFM mode. In PFM mode, the quiescent input current is as low as 180μA (AUXVCC connected to VOUT). The load boundary between PFM and PWM can be programmed to cover wide applications.

The low-side driver can be either used to drive an external low-side MOSFET for a synchronous buck or left unused for a standard non-synchronous buck. The low-side driver can also be used to drive a boost converter as a preregulator followed by a buck controlled by the same IC, which greatly expands the operating input voltage range down to 2.5V or lower (Refer to “Typical Application Schematic III - Boost Buck Converter” on page 6).

The ISL85403 offers the most robust current protections. It uses peak current mode control with cycle-by-cycle current limiting. It is implemented with frequency foldback under current limit condition; also, the hiccup overcurrent mode is also implemented to guarantee reliable operations under harsh short conditions. The ISL85403 has comprehensive protections against various faults including overvoltage and over-temperature protections, etc.

KEY FEATURES

  • Buck mode: input voltage range 3V to 40V
  • Boost mode expands operating input voltage lower than 2.5V
  • Selectable forced PWM mode or PFM mode
  • 300μA IC quiescent current (PFM, no load); 180μA input quiescent current (PFM, no load, VOUT tied to AUXVCC)
  • Less than 5μA (MAX) shutdown input current (IC disabled)
  • Operational topologies
  • Synchronous buck
  • Non-synchronous buck
  • Two-stage boost buck
  • Non-inverting single inductor buck boost
  • Programmable frequency from 200kHz to 2.2MHz and frequency synchronization capability
  • ±1% tight voltage regulation accuracy
  • Reliable overcurrent protection
  • Temperature compensated current sense
  • Cycle-by-cycle current limiting with frequency foldback
  • Hiccup mode for worst case short condition
  • 20 Ld 4x4 QFN package
  • Pb-free (RoHS compliant)

BLOCK DIAGRAM

 Block Diagram

PARAMETRICS

Parameters
ISL85403
Topology
Buck or Boost
Max Duty Cycle (%)
-
# of Outputs
1
Qualification Level
Standard
Input Voltage Min (V)
3
Peak Efficiency (%)
96
Input Voltage Max (V)
40
POR
Yes
Output Voltage Min (V)
0.8
SYNCH Capability
Yes
Output Voltage Max (V)
36
Control Type
Current Mode
Output Current Max (A)
2.5
Switching Frequency Range (MHz)
0.2 to 2.2MHz
IQ
300 µA
Can Sample
YES
Switching Freq. (max) (MHz)
2.2
Temperature Range
-40 to +105
Switching Freq. (min) (MHz)
0.2

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