L6731D Adjustable step-down controller with synchronous rectification dedicated to DDR memory

The controller is an integrated circuit realized in BCD5 (BiCMOS-DMOS, version 5) fabrication that provides complete control logic and protect on for high performance step-down DC-DC and niPoL converters.

It is designed to drive N-channel MOSFETs in a synchronous rectified buck topology. The output voltage of the converter can be precisely regulated down to 600 mV with a maximum tolerance of ±0.8 %. If an external reference is used, it will be transferred divided by 2 to the N.I. input of the error-amplifier, in accordance to the DDR memory specifications.

An internal resistor divider and a voltage buffer allow to achieve an accuracy of 1 % on both Vtt and Vttref. It's possible to provide an external reference from 0V to 2.5 V in order to meet the specification for DDRI and DDRII. The input voltage can range from 1.8 V to 14 V, while the supply voltage can range from 4.5 V to 14 V. High peak current gate drivers provide for fast switching to the external power section, and the output current can be in excess of 20 A.

The PWM duty cycle can range from 0 % to 100 % with a minimum on-time (TON, MIN) lower than 100 ns making possible conversions with very low duty cycle at high switching frequency. The device provides voltage-mode control that includes a selectable frequency oscillator (250 kHz or 500 kHz).

The error amplifier features a 10 MHz gain-bandwidth-product and 5 V/µs slew-rate that permits to realize high converter bandwidth for fast transient response. The device monitors the current by using the RDS(on) of both the high-side and low-side MOSFET(s), eliminating the need for a current sensing resistor and guaranteeing an effective over-current-protection in all the application conditions.

When necessary, two different current limit protections can be externally set through two external resistors. During the soft-start phase a constant current protection is provided while after the soft-start the device enters in hiccup mode in case of over-current. The converter can always sink current. Other features are power good, not latched over-voltage-protection, feed-back disconnection and thermal shutdown. The HTSSOP16 package allows the realization of really compact DC/DC converters

技术特性

Input voltage range from 1.8V to 14V
Supply voltage range from 4.5V to 14V
Adjustable output voltage down to 0.6V with ±0.8% Accuracy over line voltage and temperature (0˚C~125˚C)
Fixed frequency voltage mode control
TON lower than 100ns
0% to 100% duty cycle
VDDR input sense
Regulates V TT and VTTREF within 1% of VDDQ
Soft-start and inhibit
High current embedded drivers
Predictive anti-cross conduction control
Programmable high-side and low-side R DS(on) sense over-current-protection
Selectable switching frequency 250KHz/500KHz
Power good output
Sink/source capability for ddr memory and termination supply
Over voltage protection
Thermal shut-down
Package: HTSSOP16

功能框图

L6731D 订购信息

订购型号	产品状态	美金价格	数量	封装	包装形式	温度范围	材料声明
L6731DTR	Active		1000	HTSSOP16	Tape And Reel
L6731D	Active		1000	HTSSOP16	Tube

DATASHEET

描述	版本	大小
L6731D : DS4565: Adjustable step-down controller with synchronous rectification dedicated to DDR memory	3	381KB