LT8643S

RECOMMENDED FOR NEW DESIGNS

42V, 6A Synchronous Step-Down Silent Switcher 2 with 2.5μA Quiescent Current

Analog Devices LT8643S Product Info

10 February 2026 4

Features

Silent Switcher ^®2 Architecture
- Ultralow EMI Emissions on Any PCB
- Eliminates PCB Layout Sensitivity
- Internal Bypass Capacitors Reduce Radiated EMI
- Optional Spread Spectrum Modulation
High Efficiency at High Frequency
- Up to 96% Efficiency at 1MHz, 12V_IN to 5V_OUT
- Up to 95% Efficiency at 2MHz, 12V_IN to 5V_OUT
Wide Input Voltage Range: 3.4V to 42V
Output Voltage Range: 0.97V to 10V(LT8640S/LT8643S); 0.97V to (V_IN – 0.5V) (LT8640SA/LT8643SA)
6A Maximum Continuous, 7A Peak Output
Ultralow Quiescent Current Burst Mode^® Operation
- 2.5µA IQ Regulating 12V_IN to 3.3V_OUT (LT8640S/LT8640SA)
- Output Ripple < 10mV_P-P

External Compensation: Fast Transient Response and Current Sharing (LT8643S)
Robust High V_OUT Operation (LT8640SA/LT8643SA)
- Safely Tolerates High Reverse Current
Fast Minimum Switch On-Time: 30ns
Low Dropout Under All Conditions: 100mV at 1A
Forced Continuous Mode
Adjustable and Synchronizable: 200kHz to 3MHz
Output Soft-Start and Tracking
Small 24-Lead 4mm × 4mm LQFN Package
AEC-Q100 Qualified for Automotive Applications

Part details & applications

The LT^®8640S/LT8643S/LT8640SA/LT8643SA synchronous step-down regulator features second generation Silent Switcher architecture designed to minimize EMI emissions while delivering high efficiency at high switching frequencies. This includes the integration of bypass capacitors to optimize all the fast current loops inside and make it easy to achieve advertised EMI performance by reducing layout sensitivity. This performance makes the LT8640S/LT8643S/LT8640SA/LT8643SA ideal for noise-sensitive applications and environments.

Peak current mode control with a 30ns minimum on-time allows high step-down ratios even at high switching frequencies. The LT8643S/LT8643SA has external compensation to enable current sharing and fast transient response at high switching frequencies.

Burst Mode operation enables ultralow standby current consumption, forced continuous mode can control frequency harmonics across the entire output load range, or spread
spectrum operation can further reduce EMI emissions.

Applications

Automotive and Industrial Supplies

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