Datasheet LT8645S, LT8646S (Analog Devices)
| Manufacturer | Analog Devices |
| Description | 65V, 8A Synchronous Step-Down Silent Switcher 2 with 2.5μA Quiescent Current |
| Pages / Page | 30 / 1 — Silent Switcher®2 Architecture. Ultralow EMI/EMC Emissions on Any PCB. … |
| File Format / Size | PDF / 457 Kb |
| Document Language | English |
Silent Switcher®2 Architecture. Ultralow EMI/EMC Emissions on Any PCB. Eliminates PCB Layout Sensitivity
Text Version of Document
LT8645S/LT8646S 65V, 8A Synchronous Step-Down Silent Switcher 2 with 2.5µA Quiescent Current FEATURES DESCRIPTION n
Silent Switcher®2 Architecture
The LT®8645S/LT8646S synchronous step-down regulator n
Ultralow EMI/EMC Emissions on Any PCB
features second generation Silent Switcher architecture n
Eliminates PCB Layout Sensitivity
designed to minimize EMI/EMC emissions while delivering n
Internal Bypass Capacitors Reduce Radiated EMI
high efficiency at high switching frequencies. This includes n
Optional Spread Spectrum Modulation
the integration of bypass capacitors to optimize all the fast n
High Efficiency at High Frequency
current loops inside and make it easy to achieve advertised n
Up to 95% Efficiency at 1MHz, 12VIN to 5VOUT
EMI performance by eliminating layout sensitivity. This n
Up to 94% Efficiency at 2MHz, 12VIN to 5VOUT
performance makes the LT8645S/LT8646S ideal for noise n
Wide Input Voltage Range: 3.4V to 65V
sensitive applications and environments. n
Ultralow Quiescent Current Burst Mode Operation
n The fast, clean, low-overshoot switching edges enable
2.5μA IQ Regulating 12VIN to 3.3VOUT (LT8645S)
n high efficiency operation even at high switching frequen-
Output Ripple < 10mVP-P
n cies, leading to a small overall solution size. Peak current
External Compensation: Fast Transient Response
mode control with a 40ns minimum on-time allows high
and Current Sharing (LT8646S)
n step-down ratios even at high switching frequencies. The Fast Minimum Switch On-Time: 40ns n LT8646S has external compensation via the VC pin to en- Low Dropout Under All Conditions: 60mV at 1A n able current sharing and fast transient response at high Adjustable and Synchronizable: 200kHz to 2.2MHz n switching frequencies. A CLKOUT pin enables synchroniz- Peak Current Mode Operation n ing other regulators to the LT8645S/LT8646S. Output Soft-Start and Tracking n Small 32-Lead 6mm × 4mm LQFN Package Burst Mode® operation enables ultralow standby current consumption, pulse-skipping mode allows full switching APPLICATIONS frequency at lower output loads, or spread spectrum n operation can further reduce EMI/EMC emissions. Automotive and Industrial Supplies All registered trademarks and trademarks are the property of their respective owners. Protected n General Purpose Step-Down by U.S. patents, including 8823345. n GSM Power Supplies TYPICAL APPLICATION
12VIN to 5VOUT Efficiency 5V 8A Step-Down Converter
100 4.0 2.2µH 95 3.5 V VOUT IN VIN SW 5.5V TO 65V 5V 90 EFFICIENCY 3.0 8A 4.7µF POWER LOSS (W) EN/UV BIAS 85 2.5 LT8645S 2.2pF 1M 80 2.0 100µF 75 1.5 RT FB EFFICIENCY (%) POWER LOSS 70 1.0 41.2k GND 243k 65 1MHz, L = 2.2µH 0.5 8645S TA01a 2MHz, L = 1µH fSW = 1MHz 60 0 1 2 3 4 5 6 7 8 LOAD CURRENT (A) 8645S TA01b 8645Sfa For more information www.linear.com/LT8645S 1
Silent Switcher®2 Architecture
The LT®8645S/LT8646S synchronous step-down regulator n
Ultralow EMI/EMC Emissions on Any PCB
features second generation Silent Switcher architecture n
Eliminates PCB Layout Sensitivity
designed to minimize EMI/EMC emissions while delivering n
Internal Bypass Capacitors Reduce Radiated EMI
high efficiency at high switching frequencies. This includes n
Optional Spread Spectrum Modulation
the integration of bypass capacitors to optimize all the fast n
High Efficiency at High Frequency
current loops inside and make it easy to achieve advertised n
Up to 95% Efficiency at 1MHz, 12VIN to 5VOUT
EMI performance by eliminating layout sensitivity. This n
Up to 94% Efficiency at 2MHz, 12VIN to 5VOUT
performance makes the LT8645S/LT8646S ideal for noise n
Wide Input Voltage Range: 3.4V to 65V
sensitive applications and environments. n
Ultralow Quiescent Current Burst Mode Operation
n The fast, clean, low-overshoot switching edges enable
2.5μA IQ Regulating 12VIN to 3.3VOUT (LT8645S)
n high efficiency operation even at high switching frequen-
Output Ripple < 10mVP-P
n cies, leading to a small overall solution size. Peak current
External Compensation: Fast Transient Response
mode control with a 40ns minimum on-time allows high
and Current Sharing (LT8646S)
n step-down ratios even at high switching frequencies. The Fast Minimum Switch On-Time: 40ns n LT8646S has external compensation via the VC pin to en- Low Dropout Under All Conditions: 60mV at 1A n able current sharing and fast transient response at high Adjustable and Synchronizable: 200kHz to 2.2MHz n switching frequencies. A CLKOUT pin enables synchroniz- Peak Current Mode Operation n ing other regulators to the LT8645S/LT8646S. Output Soft-Start and Tracking n Small 32-Lead 6mm × 4mm LQFN Package Burst Mode® operation enables ultralow standby current consumption, pulse-skipping mode allows full switching APPLICATIONS frequency at lower output loads, or spread spectrum n operation can further reduce EMI/EMC emissions. Automotive and Industrial Supplies All registered trademarks and trademarks are the property of their respective owners. Protected n General Purpose Step-Down by U.S. patents, including 8823345. n GSM Power Supplies TYPICAL APPLICATION
12VIN to 5VOUT Efficiency 5V 8A Step-Down Converter
100 4.0 2.2µH 95 3.5 V VOUT IN VIN SW 5.5V TO 65V 5V 90 EFFICIENCY 3.0 8A 4.7µF POWER LOSS (W) EN/UV BIAS 85 2.5 LT8645S 2.2pF 1M 80 2.0 100µF 75 1.5 RT FB EFFICIENCY (%) POWER LOSS 70 1.0 41.2k GND 243k 65 1MHz, L = 2.2µH 0.5 8645S TA01a 2MHz, L = 1µH fSW = 1MHz 60 0 1 2 3 4 5 6 7 8 LOAD CURRENT (A) 8645S TA01b 8645Sfa For more information www.linear.com/LT8645S 1
