Abstract
This article introduces a small, powerful, and quiet monolithic synchronous boost converter. It highlights several features of this integrated circuit that enhance its performance and offer customization to meet the requirements of various applications.
Introduction
Traditional synchronous boost converters offer little to no protec- tion against short-circuit events at the output. Due to the boost converter’s topology, when the output is shorted to ground, a direct path from input to ground is created, resulting in a large cur- rent draw that can be catastrophic to the device. In contrast, this monolithic synchronous boost converter features a short-circuit protection function that can monitor and disconnect the input in the event of a short-circuit, thus protecting the device from poten- tial damage.
The LT8342 integrates 40 V, 9 A power switches with a program- mable output voltage of up to 36 V. It also supports a wide 2.8 V to 40 V input voltage range and includes PassThruTM mode opera- tion for conditions when VIN ≥ VOUT. This integrated circuit (IC) has low VIN pin quiescent current in Burst Mode operation and can be programmed or synchronized up to 3 MHz, reducing the size of external components and core solution size. The device utilizes Silent Switcher architecture to minimize electromagnetic interfer- ence (EMI) emissions while delivering high efficiency, and it comes in a compact 4 mm × 4 mm LQFN package.
High Performance 24 V, 3 A Supply
Figure 1 shows a 24 V boost application with output short-circuit protection implemented. It can supply a maximum load current of 3 A when the input voltage is above 12 V, and the switching frequency is set to 2 MHz when a 15 kΩ resistor is placed at the RT pin.
short-circuit protection.
By configuring the SYNC/MODE pin, this boost converter can operate in either Burst Mode or pulse-skipping mode, depending on the application’s needs. Burst Mode provides higher efficiency during light-load conditions, while pulse-skipping mode reduces output ripple. Figure 2 shows the efficiency of the 24 V applica- tion operating in Burst Mode when SYNC/MODE = 0 V. Efficiency remains above 70% under light-load conditions and can reach a peak of over 95% at 3 A when the input voltage is 20 V.
(SYNC/MODE = 0 V).
Low IQ Current
In Burst Mode operation, the LT8342 delivers small single pulses of current to maintain the output voltage, followed by a sleep period. During this sleep period, the VIN pin consumes only 9 μA without short-circuit protection enabled, or 28 μA when short- circuit protection is active. As the load decreases, the device spends a greater percentage of time in sleep mode, improving efficiency at lighter loads. Additionally, when the IC is in shut- down mode, it consumes just 350 nA of input quiescent current.
CISPR 25 Class 5 Emissions Results
This IC features an optional spread spectrum frequency modula- tion (SSFM) mode, along with the Silent Switcher architecture, to further minimize EMI emissions. When SSFM is enabled by con- figuring the SYNC/MODE pin, the internal oscillator frequency varies between its programmed value and a value approximately 13% higher. Conducted and radiated EMI results, in accordance with the CISPR 25 Class 5 standards, are shown in figures 3 and 4, respectively. SSFM can also be activated in Burst Mode or pulse-skipping modes to provide both low EMI and high efficiency.
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