LTC7871

Six-Phase, Synchronous Bidirectional Buck or Boost Controller

Manufacturer

adi

Overview

Part: LTC7871 from Analog Devices

Type: Six-Phase, Synchronous Bidirectional Buck or Boost Controller

Key Specs:

V_HIGH Supply Voltage Range: 6V to 100V
V_LOW Supply Voltage Range: 1.2V to 60V
Efficiency: Up to 98%
Voltage Regulation Accuracy: ±1% Overtemperature
Phase-Lockable Frequency: 60kHz to 750kHz
Operating Junction Temperature Range: -40°C to 150°C

Features:

Unique Architecture Allows Dynamic Regulation of Input Voltage, Output Voltage or Current
Operates with External Gate Drivers and MOSFETs
Synchronous Rectification: Up to 98% Efficiency
ADI-Proprietary Advanced Current Mode Control
±1% Voltage Regulation Accuracy Overtemperature
Accurate, Programmable Inductor Current Monitoring and Bidirectional Regulation
SPI Compliant Serial Interface
Phase-Lockable Frequency: 60kHz to 750kHz
Optional Spread Spectrum Modulation
Multiphase/Multi-ICs Operation Up to 24 Phases
Selectable CCM/DCM/Burst Mode Operation
Thermally Enhanced 64-Lead LQFP Package
AEC-Q100 Qualification in Progress

Applications:

Automotive 48V/12V Dual Battery Systems
Backup Power Systems

Package:

64-Lead (10mm × 10mm) Plastic LQFP

Features

Unique Architecture Allows Dynamic Regulation of Input Voltage, Output Voltage or Current
Operates with External Gate Drivers and MOSFETs
V_HIGH Voltages Up to 100V; V_LOW Voltages Up to 60V
Synchronous Rectification: Up to 98% Efficiency
ADI-Proprietary Advanced Current Mode Control
±1% Voltage Regulation Accuracy Overtemperature
Accurate, Programmable Inductor Current Monitoring and Bidirectional Regulation
SPI Compliant Serial Interface
- Operation Status and Fault Report
- Programmable V_HIGH, V_LOW Margining
Phase-Lockable Frequency: 60kHz to 750kHz
Optional Spread Spectrum Modulation
Multiphase/Multi-ICs Operation Up to 24 Phases
Selectable CCM/DCM/Burst Mode Operation
Thermally Enhanced 64-Lead LQFP Package
AEC-Q100 Qualification in Progress

Applications

Automotive 48V/12V Dual Battery Systems
Backup Power Systems

DESCRIPTION

The LTC®7871 is a high performance bidirectional buck or boost switching regulator controller that operates in either buck or boost mode on demand. It regulates in buck mode from V_HIGH -to- V_LOW and boost mode from V_LOW -to- V_HIGH depending on a control signal, making it ideal for 48V/12V automotive dual battery systems. An accurate current programming loop regulates the maximum current that can be delivered in either direction. The LTC7871 allows both batteries to supply energy to the load simultaneously by driving energy from either battery to the other.

Its proprietary constant frequency current mode architecture enhances the signal-to-noise ratio enabling low noise operation and provides excellent current matching between phases. Additional features include an SPI-compliant serial interface, discontinuous or continuous mode of operation, OV/UV monitors, independent loop compensation for buck and boost operation, accurate inductor current monitoring and overcurrent protection.

The LTC7871 is available in a 64 pin 10mm × 10mm LWE package.

All registered trademarks and trademarks are the property of their respective owners.

TYPICAL APPLICATION

High Voltage Bidirectional Controller with Programming and Monitoring Functions

Boost-to-Buck Transition

Rev. B

Pin Configuration

Electrical Characteristics

SYMBOL	PARAMETER	CONDITIONS		MIN	TYP	MAX	UNITS
Main Contro	l Loops		-
V _HIGH	V _HIGH Supply Voltage Range			6		100	V
overline{V_LOW}	V _LOW Supply Voltage Range	V _HIGH > 6V		1.2		60	V
	V _LOW Regulated Feedback Voltage	(Note 4); ITH _LOW Voltage = 1.5V	•	1.188	1.200	1.212	V
	V _HIGH Regulated Feedback Voltage	(Note 4); ITH _HIGH Voltage = 0.5V	•	1.188	1.200	1.212	V
	V _LOW EA Feedback Current	(Note 4)			-10	-40	nA
	V _HIGH EA Feedback Current	(Note 4)			-10	-40	nA
	Reference Voltage Line Regulation	(Note 4); V _HIGH = 7V to 80V			0.02	0.2	%
	V _HIGH /V _LOW Voltage Load Regulation	Measured in Servo Loop, Δ ITH Voltage = 1.0V to 1.5V Measured in Servo Loop, Δ ITH Voltage = 1.0V to 0.5V			0.01 -0.01	0.2 -0.2	% %
g _m-buck	Buck Mode Transconductance Amplifier g _m-buck	(Note 4) ITH _LOW = 1.5V, Sink/Source 5μA			2		mmho
g _m-boost	Boost Mode Transconductance Amplifier g _m-boost	(Note 4) ITH _HIGH = 0.5V, Sink/Source 5μA			1		mmho
IQ	V _HIGH DC Supply Current Shutdown Mode, V _HIGH Supply Current Shutdown Mode, V _LOW Supply Current	(Note 5) V _RUN = 0V; V _HIGH = 48V V _RUN = 0V; V _LOW = 12V			10 30 20	16	mA μA μA
UVLO	DRV _CC Undervoltage Lockout Threshold	DRV _CC Ramping Down, V _DRVSET = V _V5 DRV _CC Ramping Down, V _DRVSET = Float DRV _CC Ramping Down, V _DRVSET = 0V		6.9 4.8 3.9	7.2 5.0 4.1	7.5 5.2 4.3	V V V
	DRV _CC Undervoltage Hysteresis	V _DRVSET = Float, V _V5 V _DRVSET = 0V			0.8 0.5		V
	V5 Undervoltage Lockout Threshold	V5 Ramping Down, V _DRVSET = Float, V _V5 V5 Ramping Down, V _DRVSET = 0V		4.2 3.9	4.4 4.1	4.6 4.3	V
	V5 Undervoltage Hysteresis	V _DRVSET = Float, V _V5 V _DRVSET = 0V			0.2 0.5		V
	RUN Pin On Threshold	V _RUN Rising		1.1	1.22	1.35	V
	RUN Pin On Hysteresis				80		mV
	RUN Pin Source Current	V _RUN < 1.1V	•	0.6	2		μA
	RUN Pin Hysteresis Current	V _RUN > 1.3V	•	2	6		μA
I _SS	Soft-Start Charging Current	V _SS = 1.2V		0.8	1.0	1.2	μA
	BUCK Pin Input Threshold	V _BUCK Rising V _BUCK Falling			2.2 1.7		V
	BUCK Pin Pull-Up Resistance	BUCK Pin to V5			200		kΩ
	Maximum Duty Cycle	Buck Mode Boost Mode		96	98 92		% %
Current Mon	nitoring and Regulation Functions					_
I _SNSA +	SNSA+ Pins Input Current				±0.05	±1	μA
I _SNSD +	SNSD+ Pins Input Current				±0.05	±1	μA
I _SNS -	SNS ^- Pins Input Current				1		mA
	ILIM Pin Input Resistance				100		kΩ
I _SETCUR	SETCUR Pin Sourcing Current	MFR_IDAC_SETCUR = 0x00	•	15.0	16.0	17.0	μA
	IMON Current Proportional to V _LOW at Max Current	V_ILIM = Float, R_SENSE = 3mΩ				±10	%
	I _MON Zero Current Voltage			1.240	1.250	1.260	V

Thermal Information

The LTC7871 has a temperature sensor integrated on the IC, to sense the die temperature. When the die temperature exceeds 180°C, all switching actions stop, and all PWM pins become Hi-Z, thus turning off all external MOSFETs. At the same time, all the channels are disconnected from the IMON pins, and the SS and ITHHIGH/ ITHLOW pins continue to function normally, so as not to interfere with other LTC7871 chips that may reference the common pins. When the temperature drops 15°C below the trip threshold, normal operation resumes.

The Typical Application on the first page of this data sheet is a basic LTC7871 application circuit. In general, external component selection is driven by the load requirements, and begins with the DCR or RSENSE and inductor value. Next, power MOSFETs are selected. Finally, VHIGH and VLOW capacitors are selected.

Data on this page is extracted from publicly available manufacturer datasheets using automated tools including AI. It may contain errors or omissions. Always verify specifications against the official manufacturer datasheet before making design or purchasing decisions. See our Terms of Service. Rights holders can submit a takedown request.

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