Datasheet LTC3458 (Analog Devices) - 8
| Fabricante | Analog Devices |
| Descripción | 1.4A, 1.5MHz Synchronous Step-Up DC/DC Converter with Output Disconnect |
| Páginas / Página | 16 / 8 — BLOCK DIAGRA. APPLICATIO S I FOR ATIO. Detailed Description. LTC3458 … |
| Formato / tamaño de archivo | PDF / 320 Kb |
| Idioma del documento | Inglés |
BLOCK DIAGRA. APPLICATIO S I FOR ATIO. Detailed Description. LTC3458 Programmable Functions. Current Limit/Peak Burst Current
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LTC3458
W BLOCK DIAGRA
BURST SW VCC 11 1 2 VCC ANTIRING SYNC 3 OSC/SYNC SLOPE UNDER VSELECT – MAX BURST MODE N-DRIVE P-DRIVE R CONTROL T 6 DUTY + MODE V SW1 BEST IZERO IZERO CLOCK DETECT PWM P-DRIVE 12 VOUT AND BURST MODE N-DRIVE P-DRIVE DRIVE LOGIC 4% UNDER UNDERVOLTAGE PGND SLEEP TO ERROR AMPLIFIER/ SLEEP SLEEP BURST COMPARATOR ALL BLOCKS CONTROL BURST ACTIVE MODE – 7 FB I PEAK VCC (DISABLED IN + FIXED I PEAK CURRENT COMP/LIMIT_PEAK BURST MODE) FREQUENCY COMPARATOR MODE BIAS I BURST MODE BURST_PEAK CURRENTS REFERENCE/ I MUX COMP, ILIMIT, I_SENSE BIAS SLOPE IBURST_PEAK, UVLO SLOPE COMP TSD VBEST SOFT-START THERMAL SD SD N-DRIVE SDB TO ALL BLOCKS PGND 9 5 13 10 8 4 3458 BD GND ILIM PGND SS COMP SHDN
U U W U APPLICATIO S I FOR ATIO Detailed Description LTC3458 Programmable Functions
The LTC3458 provides high efficiency, low noise power
Current Limit/Peak Burst Current.
The programmable for boost applications with output voltages up to 7.5V. The current limit circuit sets the maximum peak current in the true output disconnect feature eliminates inrush current, internal N-channel MOSFET switch. This clamp level is and allows VOUT to go to zero during shutdown. The programmed using a resistor to ground on ILIM. In Burst current mode architecture with adaptive slope compensa- Mode operation, the current limit is automatically set to tion provides ease of loop compensation with excellent ~1/4 of the programmed current limit for optimal effi- transient load response. The low RDS(ON), low gate charge ciency. A 124k RILIM resistor is recommended in most synchronous switches eliminate the need for an external applications unless a lower limit is needed to prevent the Schottky rectifier, and provide efficient high frequency external inductor from saturating. pulse width modulation (PWM) control. High efficiency is achieved at light loads when Burst Mode operation is ILIM = 200 entered, where the IC’s quiescent current is a low 15μA R typical on VIN. The LTC3458 is designed to provide custom I is in amps and R is in kΩ. performance in a variety of applications with program- mable feedback, current limit, oscillator frequency, soft- start, and Burst Mode threshold. I ≈ 1 •I BURSTPEAK LIM 4 3458fa 8
W BLOCK DIAGRA
BURST SW VCC 11 1 2 VCC ANTIRING SYNC 3 OSC/SYNC SLOPE UNDER VSELECT – MAX BURST MODE N-DRIVE P-DRIVE R CONTROL T 6 DUTY + MODE V SW1 BEST IZERO IZERO CLOCK DETECT PWM P-DRIVE 12 VOUT AND BURST MODE N-DRIVE P-DRIVE DRIVE LOGIC 4% UNDER UNDERVOLTAGE PGND SLEEP TO ERROR AMPLIFIER/ SLEEP SLEEP BURST COMPARATOR ALL BLOCKS CONTROL BURST ACTIVE MODE – 7 FB I PEAK VCC (DISABLED IN + FIXED I PEAK CURRENT COMP/LIMIT_PEAK BURST MODE) FREQUENCY COMPARATOR MODE BIAS I BURST MODE BURST_PEAK CURRENTS REFERENCE/ I MUX COMP, ILIMIT, I_SENSE BIAS SLOPE IBURST_PEAK, UVLO SLOPE COMP TSD VBEST SOFT-START THERMAL SD SD N-DRIVE SDB TO ALL BLOCKS PGND 9 5 13 10 8 4 3458 BD GND ILIM PGND SS COMP SHDN
U U W U APPLICATIO S I FOR ATIO Detailed Description LTC3458 Programmable Functions
The LTC3458 provides high efficiency, low noise power
Current Limit/Peak Burst Current.
The programmable for boost applications with output voltages up to 7.5V. The current limit circuit sets the maximum peak current in the true output disconnect feature eliminates inrush current, internal N-channel MOSFET switch. This clamp level is and allows VOUT to go to zero during shutdown. The programmed using a resistor to ground on ILIM. In Burst current mode architecture with adaptive slope compensa- Mode operation, the current limit is automatically set to tion provides ease of loop compensation with excellent ~1/4 of the programmed current limit for optimal effi- transient load response. The low RDS(ON), low gate charge ciency. A 124k RILIM resistor is recommended in most synchronous switches eliminate the need for an external applications unless a lower limit is needed to prevent the Schottky rectifier, and provide efficient high frequency external inductor from saturating. pulse width modulation (PWM) control. High efficiency is achieved at light loads when Burst Mode operation is ILIM = 200 entered, where the IC’s quiescent current is a low 15μA R typical on VIN. The LTC3458 is designed to provide custom I is in amps and R is in kΩ. performance in a variety of applications with program- mable feedback, current limit, oscillator frequency, soft- start, and Burst Mode threshold. I ≈ 1 •I BURSTPEAK LIM 4 3458fa 8