Datasheet LT8645S, LT8646S (Analog Devices)
| Hersteller | Analog Devices |
| Beschreibung | 65V, 8A Synchronous Step-Down Silent Switcher 2 with 2.5μA Quiescent Current |
| Seiten / Seite | 30 / 1 — FEATURES. DESCRIPTION. Silent Switcher®2 Architecture. Ultralow EMI … |
| Revision | B |
| Dateiformat / Größe | PDF / 2.4 Mb |
| Dokumentensprache | Englisch |
FEATURES. DESCRIPTION. Silent Switcher®2 Architecture. Ultralow EMI Emissions on Any PCB. Eliminates PCB Layout Sensitivity
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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 Emissions on Any PCB
features second generation Silent Switcher architecture n
Eliminates PCB Layout Sensitivity
designed to minimize EMI emissions while delivering high n
Internal Bypass Capacitors Reduce Radiated EMI
efficiency at high switching frequencies. This includes the n
Optional Spread Spectrum Modulation
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. n
Up to 94% Efficiency at 2MHz, 12VIN to 5VOUT
The fast, clean, low-overshoot switching edges enable n
Wide Input Voltage Range: 3.4V to 65V
n high efficiency operation even at high switching frequen-
Ultralow Quiescent Current Burst Mode Operation
n cies, leading to a small overall solution size. Peak current
2.5μA IQ Regulating 12VIN to 3.3VOUT (LT8645S)
n mode control with a 40ns minimum on-time allows high
Output Ripple < 10mVP-P
n step-down ratios even at high switching frequencies. The
External Compensation: Fast Transient Response
LT8646S has external compensation to enable current
and Current Sharing (LT8646S)
n sharing and fast transient response at high switching Fast Minimum Switch On-Time: 40ns n frequencies. Low Dropout Under All Conditions: 60mV at 1A n Adjustable and Synchronizable: 200kHz to 2.2MHz Burst Mode® operation enables ultralow standby current n Peak Current Mode Operation consumption, pulse-skipping mode allows full switching n Output Soft-Start and Tracking frequency at lower output loads, or spread spectrum n Small 32-Lead 6mm × 4mm LQFN Package operation can further reduce EMI emissions. n AEC-Q100 Qualified for Automotive Applications
INTERNAL CAPS VC COMP 150°C GRADE
LT8645S Yes Internal No
APPLICATIONS
LT8646S Yes External No n Automotive and Industrial Supplies LT8645S-2* No Internal Yes n General Purpose Step-Down *See LT8645S-2 Data Sheet n GSM Power Supplies All registered trademarks and trademarks are the property of their respective owners. Protected by U.S. patents, including 8823345.
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 Rev. B Document Feedback For more information www.analog.com 1 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Package Description Revision History Typical Applications Related Parts
FEATURES DESCRIPTION
n
Silent Switcher®2 Architecture
The LT®8645S/LT8646S synchronous step-down regulator n
Ultralow EMI Emissions on Any PCB
features second generation Silent Switcher architecture n
Eliminates PCB Layout Sensitivity
designed to minimize EMI emissions while delivering high n
Internal Bypass Capacitors Reduce Radiated EMI
efficiency at high switching frequencies. This includes the n
Optional Spread Spectrum Modulation
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. n
Up to 94% Efficiency at 2MHz, 12VIN to 5VOUT
The fast, clean, low-overshoot switching edges enable n
Wide Input Voltage Range: 3.4V to 65V
n high efficiency operation even at high switching frequen-
Ultralow Quiescent Current Burst Mode Operation
n cies, leading to a small overall solution size. Peak current
2.5μA IQ Regulating 12VIN to 3.3VOUT (LT8645S)
n mode control with a 40ns minimum on-time allows high
Output Ripple < 10mVP-P
n step-down ratios even at high switching frequencies. The
External Compensation: Fast Transient Response
LT8646S has external compensation to enable current
and Current Sharing (LT8646S)
n sharing and fast transient response at high switching Fast Minimum Switch On-Time: 40ns n frequencies. Low Dropout Under All Conditions: 60mV at 1A n Adjustable and Synchronizable: 200kHz to 2.2MHz Burst Mode® operation enables ultralow standby current n Peak Current Mode Operation consumption, pulse-skipping mode allows full switching n Output Soft-Start and Tracking frequency at lower output loads, or spread spectrum n Small 32-Lead 6mm × 4mm LQFN Package operation can further reduce EMI emissions. n AEC-Q100 Qualified for Automotive Applications
INTERNAL CAPS VC COMP 150°C GRADE
LT8645S Yes Internal No
APPLICATIONS
LT8646S Yes External No n Automotive and Industrial Supplies LT8645S-2* No Internal Yes n General Purpose Step-Down *See LT8645S-2 Data Sheet n GSM Power Supplies All registered trademarks and trademarks are the property of their respective owners. Protected by U.S. patents, including 8823345.
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 Rev. B Document Feedback For more information www.analog.com 1 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Package Description Revision History Typical Applications Related Parts