Datasheet LTC3809-1 (Analog Devices) - 7
| Hersteller | Analog Devices |
| Beschreibung | No RSENSE , Low Input Voltage, Synchronous DC/DC Controller with Output Tracking |
| Seiten / Seite | 24 / 7 — PIN FUNCTIONS. MODE (Pin 1):. IPRG (Pin 6):. Do not. BG (Pin 7):. leave … |
| Dateiformat / Größe | PDF / 267 Kb |
| Dokumentensprache | Englisch |
PIN FUNCTIONS. MODE (Pin 1):. IPRG (Pin 6):. Do not. BG (Pin 7):. leave this pin fl oating. TRACK/SS (Pin 2):. TG (Pin 8):. IN (Pin 9):
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LTC3809-1
PIN FUNCTIONS MODE (Pin 1):
This pin performs two functions: 1) auxiliary
IPRG (Pin 6):
Three-State Pin to Select Maximum Peak winding feedback input, and 2) Burst Mode operation, Sense Voltage Threshold. This pin selects the maximum pulse skipping or forced continuous mode select. allowed voltage drop between the VIN and SW pins (i.e., the maximum allowed drop across the external To select Burst Mode operation at light loads, tie this P-channel MOSFET). Tie to V pin to V IN, GND or fl oat to select IN. Grounding this pin selects forced continuous 204mV, 85mV or 125mV respectively. operation which allows the inductor current to reverse. Tying this pin to VFB selects pulse-skipping mode.
Do not BG (Pin 7):
Bottom (NMOS) Gate Drive Output. This pin
leave this pin fl oating.
drives the gate of the external N-channel MOSFET. This pin has an output swing from PGND to V
TRACK/SS (Pin 2):
Tracking Input for the Controller or IN. Optional External Soft-Start Input. This pin allows the
TG (Pin 8):
Top (PMOS) Gate Drive Output. This pin drives start-up of VOUT to “track” the external voltage at this pin the gate of the external P-channel MOSFET. This pin has using an external resistor divider. Tying this pin to VIN an output swing from PGND to VIN. allows VOUT to start up with the internal 0.74ms soft-start.
V
An external soft-start can be programmed by connecting
IN (Pin 9):
Chip Signal Power Supply. This pin powers the entire chip, the gate drivers and serves as the positive a capacitor between this pin and ground.
Do not leave
input to the differential current comparator.
this pin fl oating. SW (Pin 10):
Switch Node Connection to Inductor. This
VFB (Pin 3):
Feedback Pin. This pin receives the remotely pin is also the negative input to the differential current sensed feedback voltage for the controller from an external comparator and an input to the reverse current comparator. resistor divider across the output. Normally this pin is connected to the drain of the external
ITH (Pin 4):
Current Threshold and Error Amplifi er P-channel MOSFET, the drain of the external N-channel Compensation Point. Nominal operating range on this pin MOSFET and the inductor. is from 0.7V to 2V. The voltage on this pin determines the
GND (Exposed Pad, Pin 11):
Ground connection for threshold of the main current comparator. internal circuits, the gate drivers and the negative input to
RUN (Pin 5):
Run Control Input. Forcing this pin below the reverse current comparator. The Exposed Pad must 1.1V shuts down the chip. Driving this pin to VIN or be soldered to the PCB ground. releasing this pin enables the chip to start-up with the internal soft-start. 38091fc 7
PIN FUNCTIONS MODE (Pin 1):
This pin performs two functions: 1) auxiliary
IPRG (Pin 6):
Three-State Pin to Select Maximum Peak winding feedback input, and 2) Burst Mode operation, Sense Voltage Threshold. This pin selects the maximum pulse skipping or forced continuous mode select. allowed voltage drop between the VIN and SW pins (i.e., the maximum allowed drop across the external To select Burst Mode operation at light loads, tie this P-channel MOSFET). Tie to V pin to V IN, GND or fl oat to select IN. Grounding this pin selects forced continuous 204mV, 85mV or 125mV respectively. operation which allows the inductor current to reverse. Tying this pin to VFB selects pulse-skipping mode.
Do not BG (Pin 7):
Bottom (NMOS) Gate Drive Output. This pin
leave this pin fl oating.
drives the gate of the external N-channel MOSFET. This pin has an output swing from PGND to V
TRACK/SS (Pin 2):
Tracking Input for the Controller or IN. Optional External Soft-Start Input. This pin allows the
TG (Pin 8):
Top (PMOS) Gate Drive Output. This pin drives start-up of VOUT to “track” the external voltage at this pin the gate of the external P-channel MOSFET. This pin has using an external resistor divider. Tying this pin to VIN an output swing from PGND to VIN. allows VOUT to start up with the internal 0.74ms soft-start.
V
An external soft-start can be programmed by connecting
IN (Pin 9):
Chip Signal Power Supply. This pin powers the entire chip, the gate drivers and serves as the positive a capacitor between this pin and ground.
Do not leave
input to the differential current comparator.
this pin fl oating. SW (Pin 10):
Switch Node Connection to Inductor. This
VFB (Pin 3):
Feedback Pin. This pin receives the remotely pin is also the negative input to the differential current sensed feedback voltage for the controller from an external comparator and an input to the reverse current comparator. resistor divider across the output. Normally this pin is connected to the drain of the external
ITH (Pin 4):
Current Threshold and Error Amplifi er P-channel MOSFET, the drain of the external N-channel Compensation Point. Nominal operating range on this pin MOSFET and the inductor. is from 0.7V to 2V. The voltage on this pin determines the
GND (Exposed Pad, Pin 11):
Ground connection for threshold of the main current comparator. internal circuits, the gate drivers and the negative input to
RUN (Pin 5):
Run Control Input. Forcing this pin below the reverse current comparator. The Exposed Pad must 1.1V shuts down the chip. Driving this pin to VIN or be soldered to the PCB ground. releasing this pin enables the chip to start-up with the internal soft-start. 38091fc 7