Datasheet LT8631 (Analog Devices) - 10
| Manufacturer | Analog Devices |
| Description | 100V, 1A Synchronous Micropower Step-Down Regulator |
| Pages / Page | 26 / 10 — BLOCK DIAGRAM. Figure 1. Block Diagram. OPERATION |
| File Format / Size | PDF / 375 Kb |
| Document Language | English |
BLOCK DIAGRAM. Figure 1. Block Diagram. OPERATION
Model Line for this Datasheet
Text Version of Document
LT8631
BLOCK DIAGRAM
VIN VIN – C1 R3 INTVCC VIN INTV + CC UVLO LDO 2.8 C4 FAULT 1.19 BST +UVLO EN/UV COMP S C3 – TSD POR LATCH Q R SW L1 R4 INTVCC S Q SYNC/MODE SWITCH OSCILLATOR SWITCH ON LATCH R QB LOGIC IND INEG + CURRENT ITRIP COMP VOUT VOUT RT + – REF RT RT AMP – R1 C6 R5 SLOPE COMP INTVCC 50mV + PG SS 7.5% + C5 COMP – FB – –7.5% COMP POR + 0.808 BURST DETECT VC ERROR FB – AMP SS VC CLAMP – R2 C2 GND 8631 BD
Figure 1. Block Diagram OPERATION
The LT8631 is a monolithic, constant frequency, current soft-start latch is reset. Once the latch is reset the soft-start mode step-down DC/DC converter. When the voltage on capacitor starts to charge with a typical value of 4.5µA. the EN/UV pin is below its 1.19V threshold, the LT8631 is The error amplifier is a transconductance amplifier that shutdown and draws less than 5µA from the input supply. compares the FB pin voltage to the lowest voltage present When the EN/UV pin is driven above 1.19V, the internal bias at either the TR/SS pin or an internal 0.808V reference. circuits turn on generating an internal regulated voltage, Since the TR/SS pin is driven by a constant current source, 0.808V feedback reference, a 4.5µA soft-start current a single capacitor on the soft-start pin will generate a reference, and a power on reset (POR) signal. controlled linear ramp on the output voltage. The voltage During power-up the POR signal is set and in turn sets the on the output of the error amplifier (internal VC node in soft-start latch. When the soft-start latch is set, the TR/SS Figure 1) sets the peak current of each switch cycle and pin will be discharged to ground to ensure proper start-up also determines when to enable low quiescent current operation. When the TR/SS pin drops below 50mV, the burst mode operation. 8631fb 10 For more information www.linear.com/LT8631
BLOCK DIAGRAM
VIN VIN – C1 R3 INTVCC VIN INTV + CC UVLO LDO 2.8 C4 FAULT 1.19 BST +UVLO EN/UV COMP S C3 – TSD POR LATCH Q R SW L1 R4 INTVCC S Q SYNC/MODE SWITCH OSCILLATOR SWITCH ON LATCH R QB LOGIC IND INEG + CURRENT ITRIP COMP VOUT VOUT RT + – REF RT RT AMP – R1 C6 R5 SLOPE COMP INTVCC 50mV + PG SS 7.5% + C5 COMP – FB – –7.5% COMP POR + 0.808 BURST DETECT VC ERROR FB – AMP SS VC CLAMP – R2 C2 GND 8631 BD
Figure 1. Block Diagram OPERATION
The LT8631 is a monolithic, constant frequency, current soft-start latch is reset. Once the latch is reset the soft-start mode step-down DC/DC converter. When the voltage on capacitor starts to charge with a typical value of 4.5µA. the EN/UV pin is below its 1.19V threshold, the LT8631 is The error amplifier is a transconductance amplifier that shutdown and draws less than 5µA from the input supply. compares the FB pin voltage to the lowest voltage present When the EN/UV pin is driven above 1.19V, the internal bias at either the TR/SS pin or an internal 0.808V reference. circuits turn on generating an internal regulated voltage, Since the TR/SS pin is driven by a constant current source, 0.808V feedback reference, a 4.5µA soft-start current a single capacitor on the soft-start pin will generate a reference, and a power on reset (POR) signal. controlled linear ramp on the output voltage. The voltage During power-up the POR signal is set and in turn sets the on the output of the error amplifier (internal VC node in soft-start latch. When the soft-start latch is set, the TR/SS Figure 1) sets the peak current of each switch cycle and pin will be discharged to ground to ensure proper start-up also determines when to enable low quiescent current operation. When the TR/SS pin drops below 50mV, the burst mode operation. 8631fb 10 For more information www.linear.com/LT8631
