OVERVIEW

The ISL78235 is a highly efficient, monolithic, synchronous step-down DC/DC converter that can deliver 5A of continuous output current from a 2.7V to 5.5V input supply. The device uses peak current mode control architecture to achieve very low duty cycle operation at high frequency with fast transient response and excellent loop stability.

The ISL78235 integrates a low ON-resistance P-channel (35mΩ, typical) high-side FET and N-channel (11mΩ, typical) low-side FET to maximize efficiency and minimize external component count. The 100% duty cycle operation allows less than 250mV dropout voltage at 5A output current. The operating frequency of the Pulse-Width Modulator (PWM) is adjustable from 500kHz to 4MHz. The default switching frequency of 2MHz is set by connecting the FS pin high.

The ISL78235 can be configured for discontinuous (PFM) or forced continuous (PWM) operation at light load. Forced continuous operation reduces noise and RF interference; discontinuous mode provides higher efficiency by reducing switching losses at light loads.

Fault protection is provided by internal hiccup mode current limiting during short-circuit and overcurrent conditions. The device also integrates output overvoltage and over-temperature protections. A power-good monitor indicates when the output is in regulation. The ISL78235 features a 1ms Power-Good (PG) timer at power-up. When in shutdown, the ISL78235 discharges the output capacitor through an internal 100Ω soft-stop switch. Other features include internal fixed or adjustable soft-start and internal/external compensation.

The ISL78235 is available in a 3mm x 3mm 16 Ld Thin Quad Flat No-lead (TQFN) Pb-free package and in a 5mmx5mm 16 Ld Wettable Flank Quad Flat No-Lead (WFQFN) package with an exposed pad for improved thermal performance. The ISL78235 is rated to operate across the temperature range of -40°C to +105°C in the 3mmx3mm package and -40°C to +125°C in the 5mmx5mm package.

KEY FEATURES

    • 2.7V to 5.5V input voltage range
    • 2MHz default switching frequency
    • 100ns guaranteed phase minimum on time for wide output regulation
    • Adjustable switching frequency from 500kHz to 4MHz
    • External synchronization from 1MHz to 4MHz
    • Optional PFM mode for light-load efficiency improvement
    • Very low ON-resistance HS/LS switches: 35mΩ/11mΩ
    • Internal 1ms or adjustable external soft-start
    • Soft-stop output discharge during disable
    • OTP, OCP, output OVP, and input UVLO protections
    • 1% reference accuracy over-temperature
    • Up to 95% efficiency
    • AEC-Q100 qualified
    • ISL78233 pinout family allows migration from 3A without PCB change
    • ISL78234 pinout family allows migration from 4A without PCB change
    • ISL78235 pinout family allows migration from 5A without PCB change

BLOCK DIAGRAM

 Block Diagram

PARAMETRICS

Parameters
ISL78235
Production Status
Mass Production
iSim Model
YES
Topology
Buck
# of Outputs
1
Input Voltage Min (V)
2.7
Input Voltage Max (V)
5.5
Output Voltage Min (V)
0.6
Output Voltage Max (V)
5.5
Output Current Max (A)
5
IQ
47 µA
Switching Freq. (max) (MHz)
4
Switching Freq. (min) (MHz)
0.5
Max Duty Cycle (%)
100
Qualification Level
Automotive
Peak Efficiency (%)
95
POR
Yes
SYNCH Capability
Yes
Control Type
Current Mode
Switching Frequency Range (MHz)
0.5 to 4
Can Sample
YES
Temperature Range
-40 to +125

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