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L6730B：Adjustable step-down controller with synchronous rectification

The controller is an integrated circuit designed using BiCMOS-DMOS, v5 (BCD5) technology that provides complete control logic and protection for high performance, stepdown DC/DC and niPOL converters.

It is designed to drive N-Channel MOSFETs in a synchronous rectified buck converter topology. The output voltage of the converter can be precisely regulated down to 600 mV, with a maximum tolerance of ±0.8%, or to 1.2 V, when one of the internal references is used.

It is also possible to use an external reference from 0 V to 2.5 V.

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, depending on the number of the external MOSFETs used. The PWM duty cycle can range from 0% to 100% with a minimum on-time (T_ON(MIN)) lower than 100 ns, making conversions with a very low duty cycle and very high switching frequency possible.

The device provides voltage-mode control. It includes a 400 kHz free-running oscillator that is adjustable from 100 kHz to 1 MHz. The error amplifier features a 10 MHz gain-bandwidthproduct 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 highside 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. A leading edge adjustable blanking time is also available to avoid false overcurrent- protection (OCP) intervention in every application condition.

It is possible to select the HICCUP mode or the constant current protection (L6730B) after the soft-start phase.

During this phase constant current protection is provided. It is possible to select the sinksource or the source-only mode capability (before the device powers on) by acting on a multifunction pin (L6730). The L6730 disables the sink mode capability during the soft-start in order to allow a proper start-up also in pre-biased output voltage conditions. The L6730B can always sink current and, so it can be used to supply the DDR memory BUS termination.

Other features include Master-Slave synchronization (with 180° phase shift), Power-Good with adjustable delay, over voltage-protection, feed back disconnection, selectable UVLO threshold (5 V and 12 V Bus), and thermal shutdown. The HTSSOP20 package allows the realization for very compact DC/DC converters.

Key Features

• High current embedded drivers
• Soft-start and inhibit
• Selectable uvlo threshold (5 V or 12 V BUS)
• Predictive anti-cross conduction control
• Switching frequency programmable from 100 kHz to 1 MHz
• Programmable high-side and low-side RDS(on) sense overcurrent protection
• Pre-bias start up capability (L6730)
• Master/slave synchronization with 180° phase shift
• Selectable source/sink or source only capability after soft-start (L6730)
• Power Good output with programmable delay
• Selectable constant current or hiccup mode overcurrent protection after soft-start (L6730B)
• Thermal shut-down
• Overvoltage protection with selectable latched/not-latched mode
• Package: HTSSOP20
• Selectable 0.6 V or 1.2 V internal voltage reference
• 0% to 100% duty cycle
• Input voltage range from 1.8 V to 14 V
• Adjustable output voltage down to 0.6 V with ±0.8% accuracy over line voltage and temperature (0°C~125°C)
• Supply voltage range from 4.5 V to 14 V
• tON lower than 100 ns
• External input voltage reference
• Fixed frequency voltage mode control

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