DESCRIPTION
The LT®8645S/LT8646S 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 eliminating layout sensitivity.
The fast, clean, low-overshoot switching edges enable
high efficiency operation even at high switching frequencies,
leading to a small overall solution size. Peak current
mode control with a 40ns minimum on-time allows high
step-down ratios even at high switching frequencies. The
LT8646S has external compensation to enable current
sharing and fast transient response at high switching
frequencies.
Burst Mode® operation enables ultralow standby current
consumption, pulse-skipping mode allows full switching
frequency at lower output loads, or spread spectrum
operation can further reduce EMI emissions.

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 95% Efficiency at 1MHz, 12VIN to 5VOUT
- Up to 94% Efficiency at 2MHz, 12VIN to 5VOUT
- Wide Input Voltage Range: 3.4V to 65V
- Ultralow Quiescent Current Burst Mode Operation
- 2.5μA IQ Regulating 12VIN to 3.3VOUT (LT8645S)
- Output Ripple < 10mVP-P
- External Compensation: Fast Transient Response
and Current Sharing (LT8646S)
- Fast Minimum Switch On-Time: 40ns
- Low Dropout Under All Conditions: 60mV at 1A
- Adjustable and Synchronizable: 200kHz to 2.2MHz
- Peak Current Mode Operation
- Output Soft-Start and Tracking
- Small 32-Lead 6mm × 4mm LQFN Package
- AEC-Q100 Qualified for Automotive Applications

APPLICATIONS
- Automotive and Industrial Supplies
- General Purpose Step-Down
- GSM Power Supplies