Obsolete Product(s) - Obsolete Product(s)
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/
µ
s 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 r
DS(ON)
of the upper MOSFET which eliminates the need for a current 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 typically 50
µ
A (Fsw=200KHz) and may be varied using an external resistor (R
T
) connected between
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
01111
1.475
11110
1.100
01110
1.500
11101
1.125
01101
1.525
11100
1.150
01100
1.550
11011
1.175
01011
1.575
11010
1.200
01010
1.600
11001
1.225
01001
1.625
11000
1.250
01000
1.650
10111
1.275
00111
1.675
10110
1.300
00110
1.700
10101
1.325
00101
1.725
10100
1.350
00100
1.750
10011
1.375
00011
1.775
10010
1.400
00010
1.800
10001
1.425
00001
1.825
10000
1.450
00000
1.850
f
S
200kHz
4.94 10
6
⋅
R
T
k
Ω()
-------------------------+=
Obsolete Product(s) - Obsolete Product(s)
