Datasheet LTC3891 (Analog Devices) - 9
| Fabricante | Analog Devices |
| Descripción | Low IQ, 60V Synchronous Step-Down Controller |
| Páginas / Página | 32 / 9 — PIN FUNCTIONS (QFN/eTSSOP). PLLIN/MODE (Pin 1/Pin 3):. PGOOD (Pin 9/Pin … |
| Formato / tamaño de archivo | PDF / 691 Kb |
| Idioma del documento | Inglés |
PIN FUNCTIONS (QFN/eTSSOP). PLLIN/MODE (Pin 1/Pin 3):. PGOOD (Pin 9/Pin 11):. TG (Pin 10/Pin 12):. SW (Pin 11/ Pin 13):
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LTC3891
PIN FUNCTIONS (QFN/eTSSOP) PLLIN/MODE (Pin 1/Pin 3):
External Synchronization
PGOOD (Pin 9/Pin 11):
Open-Drain Logic Output. PGOOD Input to Phase Detector and Forced Continuous Mode is pulled to ground when the voltage on the VFB pin is not Input. When an external clock is applied to this pin, the within 10% of its set point. phase-locked loop will force the rising TG signal to be
TG (Pin 10/Pin 12):
High Current Gate Drives for Top synchronized with the rising edge of the external clock, N-channel MOSFET. This is the output of floating driver and the regulator operates in forced continuous mode. with a voltage swing equal to INTV When not synchronizing to an external clock, this input CC superimposed on the switch node voltage SW. determines how the LTC3891 operates at light loads. Pull- ing this pin to ground selects Burst Mode operation. An
SW (Pin 11/ Pin 13):
Switch Node Connection to Induc- internal 100k resistor to ground also invokes Burst Mode tor. operation when the pin is floated. Tying this pin to INTVCC
BOOST (Pin 12/Pin 14):
Bootstrapped Supply to the Top- forces continuous inductor current operation. Tying this side Floating Driver. A capacitor is connected between the pin to a voltage greater than 1.2V and less than INTVCC BOOST and SW pin and a Schottky diode is tied between –1.3V selects pulse-skipping operation. the BOOST and INTVCC pins. Voltage swing at the BOOST
SGND (Pins 2, 3, Exposed Pad Pin 21/Pins 4, 5,
pin is from INTVCC to (VIN + INTVCC).
Exposed Pad Pin 21):
Small-signal ground, must be routed
BG (Pin 13/Pin 15):
High Current Gate Drive for Bottom separately from high current grounds to the common (Synchronous) N-channel MOSFET. Voltage swing at this (–) terminals of the CIN capacitor. Pins 2, 3/4, 5, must pin is from ground to INTV both be electrically connected to small signal ground for CC. proper operation.The exposed pad must be soldered to
INTVCC (Pin 14/Pin 16):
Output of the Internal Linear PCB ground for rated thermal performance. Low Dropout Regulator. The driver and control circuits are powered from this voltage source. Must be decoupled
RUN (Pin 4/Pin 6):
Digital Run Control Input. Forcing this to PGND with a minimum of 2.2µF ceramic or other low pin below 1.16V shuts down the controller. Forcing this ESR capacitor. Do not use the INTV pin below 0.7V shuts down the entire LTC3891, reducing CC pin for any other purpose. quiescent current to approximately 14µA.
EXTV SENSE– (Pin 5/Pin 7):
The (–) Input to the Differential
CC (Pin 15/Pin 17):
External Power Input to an Internal LDO Connected to INTV Current Comparator. When greater than INTV CC. This LDO supplies CC – 0.5V, the INTV SENSE– pin supplies power to the current comparator. CC power, bypassing the internal LDO powered from VIN whenever EXTVCC is higher than 4.7V. See EXTVCC
SENSE+ (Pin 6/Pin 8):
The (+) input to the differential Connection in the Applications Information section. Do current comparator is normally connected to DCR sensing not float or exceed 14V on this pin. network or current sensing resistor. The ITH pin voltage and
PGND (Pin 16/Pin 18):
Driver Power Ground. Connects to control ed offsets between the SENSE– and SENSE+ pins in the source of bottom (synchronous) N-channel MOSFET conjunction with RSENSE set the current trip threshold. and the (–) terminal of CIN.
VFB (Pin 7/Pin 9):
Receives the remotely sensed feed-
V
back voltage from an external resistive divider across
IN (Pin 17/Pin 19):
Main Supply Pin. A bypass capacitor should be tied between this pin and the SGND pins. the output.
I ITH (Pin 8/Pin 10):
Error Amplifier Outputs and Switching
LIM (Pin 18/Pin 20):
Current Comparator Sense Voltage Range Inputs. Tying this pin to SGND, FLOAT or INTV Regulator Compensation Point. The current comparator CC sets the maximum current sense threshold to one of three trip point increases with this control voltage. different levels for the comparator. 3891fa 9 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions FUNCTIONAL Diagram Operation Applications Information Package Description Revision History Typical Application Related Parts
PIN FUNCTIONS (QFN/eTSSOP) PLLIN/MODE (Pin 1/Pin 3):
External Synchronization
PGOOD (Pin 9/Pin 11):
Open-Drain Logic Output. PGOOD Input to Phase Detector and Forced Continuous Mode is pulled to ground when the voltage on the VFB pin is not Input. When an external clock is applied to this pin, the within 10% of its set point. phase-locked loop will force the rising TG signal to be
TG (Pin 10/Pin 12):
High Current Gate Drives for Top synchronized with the rising edge of the external clock, N-channel MOSFET. This is the output of floating driver and the regulator operates in forced continuous mode. with a voltage swing equal to INTV When not synchronizing to an external clock, this input CC superimposed on the switch node voltage SW. determines how the LTC3891 operates at light loads. Pull- ing this pin to ground selects Burst Mode operation. An
SW (Pin 11/ Pin 13):
Switch Node Connection to Induc- internal 100k resistor to ground also invokes Burst Mode tor. operation when the pin is floated. Tying this pin to INTVCC
BOOST (Pin 12/Pin 14):
Bootstrapped Supply to the Top- forces continuous inductor current operation. Tying this side Floating Driver. A capacitor is connected between the pin to a voltage greater than 1.2V and less than INTVCC BOOST and SW pin and a Schottky diode is tied between –1.3V selects pulse-skipping operation. the BOOST and INTVCC pins. Voltage swing at the BOOST
SGND (Pins 2, 3, Exposed Pad Pin 21/Pins 4, 5,
pin is from INTVCC to (VIN + INTVCC).
Exposed Pad Pin 21):
Small-signal ground, must be routed
BG (Pin 13/Pin 15):
High Current Gate Drive for Bottom separately from high current grounds to the common (Synchronous) N-channel MOSFET. Voltage swing at this (–) terminals of the CIN capacitor. Pins 2, 3/4, 5, must pin is from ground to INTV both be electrically connected to small signal ground for CC. proper operation.The exposed pad must be soldered to
INTVCC (Pin 14/Pin 16):
Output of the Internal Linear PCB ground for rated thermal performance. Low Dropout Regulator. The driver and control circuits are powered from this voltage source. Must be decoupled
RUN (Pin 4/Pin 6):
Digital Run Control Input. Forcing this to PGND with a minimum of 2.2µF ceramic or other low pin below 1.16V shuts down the controller. Forcing this ESR capacitor. Do not use the INTV pin below 0.7V shuts down the entire LTC3891, reducing CC pin for any other purpose. quiescent current to approximately 14µA.
EXTV SENSE– (Pin 5/Pin 7):
The (–) Input to the Differential
CC (Pin 15/Pin 17):
External Power Input to an Internal LDO Connected to INTV Current Comparator. When greater than INTV CC. This LDO supplies CC – 0.5V, the INTV SENSE– pin supplies power to the current comparator. CC power, bypassing the internal LDO powered from VIN whenever EXTVCC is higher than 4.7V. See EXTVCC
SENSE+ (Pin 6/Pin 8):
The (+) input to the differential Connection in the Applications Information section. Do current comparator is normally connected to DCR sensing not float or exceed 14V on this pin. network or current sensing resistor. The ITH pin voltage and
PGND (Pin 16/Pin 18):
Driver Power Ground. Connects to control ed offsets between the SENSE– and SENSE+ pins in the source of bottom (synchronous) N-channel MOSFET conjunction with RSENSE set the current trip threshold. and the (–) terminal of CIN.
VFB (Pin 7/Pin 9):
Receives the remotely sensed feed-
V
back voltage from an external resistive divider across
IN (Pin 17/Pin 19):
Main Supply Pin. A bypass capacitor should be tied between this pin and the SGND pins. the output.
I ITH (Pin 8/Pin 10):
Error Amplifier Outputs and Switching
LIM (Pin 18/Pin 20):
Current Comparator Sense Voltage Range Inputs. Tying this pin to SGND, FLOAT or INTV Regulator Compensation Point. The current comparator CC sets the maximum current sense threshold to one of three trip point increases with this control voltage. different levels for the comparator. 3891fa 9 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions FUNCTIONAL Diagram Operation Applications Information Package Description Revision History Typical Application Related Parts