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L6911E

Table 1. VID Setting

Device Description

The device is an integrated circuit realized in BCD technology. It provides complete control logic and protections

for a high performance step-down DC-DC converter optimized for microprocessor power supply. It is designed

to drive N Channel Mosfets in a synchronous-rectified buck topology. The device works properly with Vcc rang-

ing from 5V to 12V and regulates the output voltage starting from a 1.26V power stage supply voltage (Vin). The

output voltage of the converter can be precisely regulated, programming the VID pins, from 1.050V to 1.825V

with 25mV binary steps, with a maximum tolerance of

±1% over temperature and line voltage variations. The

device provides voltage-mode control with fast transient response. It includes a 200kHz free-running oscillator

that is adjustable from 50kHz to 1MHz. The error amplifier features a 15MHz gain-bandwidth product and 10V/

ms slew rate which permits high converter bandwidth for fast transient performance. The resulting PWM duty

cycle ranges from 0% to 100%. The device protects against over-current conditions entering in HICCUP mode.

rent sensing resistor.

The device is available in SO20 package.

Oscillator

The switching frequency is internally fixed to 200kHz. The internal oscillator generates the triangular waveform

for the PWM charging and discharging with a constant current an internal capacitor. The current delivered to the

oscillator is tipically 50

RT pin and GND or VCC. Since the RT pin is maintained at fixed voltage (typ. 1.235V), the frequency is varied

proportionally to the current sinked (forced) from (into) the pin.

In particular connecting it to GND the frequency is increased (current is sinked from the pin), according to the

following relationship:

Connecting RT to VCC=12V or to VCC=5V the frequency is reduced (current is forced into the pin), according

to the following relationships:

VID4

(25mV)

VID3

VID2

VID1

VID0

Outp ut

Voltage (V)

VID4

(25mV)

VID3

VID2

VID1

VID0

Outpu t

Voltage (V)

0

0

100

1.050

01

1

0

0

1.450

1

0

100

1.075

11

1

0

0

1.475

0

0

011

1.100

01

0

1

1

1.500

1

0

011

1.125

11

0

1

1

1.525

0

0

010

1.150

01

0

1

0

1.550

1

0

010

1.175

11

0

1

0

1.575

0

0

001

1.200

01

0

0

1

1.600

1

0

001

1.225

11

0

0

1

1.625

0

0

000

1.250

01

0

0

0

1.650

1

0

000

1.275

11

0

0

0

1.675

0

1

111

1.300

00

1

1

1

1.700

1

1

111

1.325

10

1

1

1

1.725

0

1

110

1.350

00

1

1

0

1.750

1

1

110

1.375

10

1

1

0

1.775

0

1

101

1.400

00

1

0

1

1.800

1

1

101

1.425

10

1

0

1

1.825

f

S

200kH z

4.94 10

6

⋅

R

()

-------------------------

+

=