L6725TR datasheet(10/27 Pages) STMICROELECTRONICS

No de pièce	L6725TR

Description	Low cost adjustable step-down controller

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Fabricant	STMICROELECTRONICS [STMicroelectronics]

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L6725

Device description

10/27

5

Device description

The controller

provides complete control logic and protection for flexible and cost-effective DC-

DC 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 600mV with a

maximum tolerance of ±0.8%, when the internal reference is used. The device allows also

using an external reference (0V to 2.5V) for the regulation. The device provides voltage-mode

control. The switching frequency can be set at two different values: 250KHz or 500KHz. The

error amplifier features a 10MHz gain-bandwidth-product and 5V/µs slew-rate that permits to

realize high converter bandwidth for fast transient response. The PWM duty cycle can range

from 0% to 100%. The device protects against over current conditions providing a constant-

current-protection during the soft-start phase and entering in HICCUP mode in all the other

conditions. 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. Other features are over-

voltage-protection and thermal shutdown. The device is available in SO16N package.

5.1

Oscillator

The switching frequency can be fixed to two values: 250KHz or 500KHz by setting the proper

voltage at the EAREF pin (see Table 3. Pins function and section 4.3 Internal and external

reference).

5.2

Internal LDO

An internal LDO supplies the internal circuitry of the device. The input of this stage is the VCC

pin and the output (5V) is the VCCDR pin. The LDO can be by-passed, providing directly a 5V

voltage to VCCDR. In this case VCC and VCCDR pins must be shorted together as shown in

Figure 3. VCCDR pin must be filtered with a 1uF capacitor to sustain the internal LDO during the

recharge of the bootstrap capacitor.

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