ltc3711 Linear Technology Corporation, ltc3711 Datasheet - Page 15

• Manufacturer Part Number: ltc3711
• Description: 5-bit Adjustable, Wide Operating Range, No Rsense? Step-down Controller
• Manufacturer: Linear Technology Corporation

APPLICATIO S I FOR ATIO
Output Voltage Programming
The output voltage is digitally set to levels between 0.900V
and 2.000V using the voltage identification (VID) inputs
VID0-VID4. An internal 5-bit DAC configured as a preci-
sion resistive voltage divider sets the output voltage in
increments according to Table 1. The VID codes are
compatible with Intel Mobile Pentium III processor speci-
fications. Each VID input is pulled up by an internal 2.5 A
current source from the INTV
series diode to prevent damage from VID inputs that
exceed the supply.
INTV
An internal P-channel low dropout regulator produces the
5V supply that powers the drivers and internal circuitry
within the LTC3711. The INTV
50mA RMS and must be bypassed to ground with a
minimum of 4.7 F low ESR tantalum capacitor. Good
bypassing is necessary to supply the high transient cur-
rents required by the MOSFET gate drivers. Applications
using large MOSFETs with a high input voltage and high
frequency of operation may cause the LTC3711 to exceed
its maximum junction temperature rating or RMS current
rating. Most of the supply current drives the MOSFET
gates unless an external EXTV
tinuous mode operation, this current is I
+ Q
from the equations given in Note 2 of the Electrical
Characteristics. For example, the LTC3711CGN is limited
to less than 14mA from a 30V supply:
For larger currents, consider using an external supply with
the EXTV
T
g(BOT)
J
CC
= 70 C + (14mA)(30V)(130 C/W) = 125 C
Regulator
CC
). The junction temperature can be estimated
pin.
U
U
CC
CC
CC
source is used. In con-
supply and includes a
W
pin can supply up to
GATECHG
U
= f(Q
g(TOP)
Table 1. VID Output Voltage Programming
Note: *, ** represent codes without a defined output voltage as specified by
Intel. The LTC3711 interprets these codes as valid inputs and produces output
voltages as follows: [01111] = 1.250V, [11111] = 0.900V.
VID4
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
VID3
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
VID2
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
VID1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
VID0
LTC3711
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
V
2.000V
1.950V
1.900V
1.850V
1.800V
1.750V
1.700V
1.650V
1.600V
1.550V
1.500V
1.450V
1.400V
1.350V
1.300V
1.275V
1.250V
1.225V
1.200V
1.175V
1.150V
1.125V
1.100V
1.075V
1.050V
1.025V
1.000V
0.975V
0.950V
0.925V
15
OUT
**
*
(V)
3711f