5/17

L6911D

Table 1. VID Settings

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 1.100V to 1.850V

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/

µs slew rate which permits high convert-

er 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. The device monitors the current by using

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 typically 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 sunk (forced) from (into) the pin.

In particular connecting it to GND the frequency is increased (current is sunk 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

VID3

VID2

VID1

VID0

Output

Voltage (V)

VID4

VID3

VID2

VID1

VID0

Output Voltage

(V)

11111

Output OFF

0111

1

1.475

11110

1.100

0111

0

1.500

11101

1.125

0110

1

1.525

11100

1.150

0110

0

1.550

11011

1.175

0101

1

1.575

11010

1.200

0101

0

1.600

11001

1.225

0100

1

1.625

11000

1.250

0100

0

1.650

10111

1.275

0011

1

1.675

10110

1.300

0011

0

1.700

10101

1.325

0010

1

1.725

10100

1.350

0010

0

1.750

10011

1.375

0001

1

1.775

10010

1.400

0001

0

1.800

10001

1.425

0000

1

1.825

10000

1.450

0000

0

1.850

f

S

200kH z

4.94 10

6

⋅

R

()

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

+

=