Linear Technology DEMO CIRCUIT 1672A, Quick Start Manual

Page: 1 / 13

1
DESCRIPTION
Demonstration circuit 1672A is a high efficiency,
single phase, synchronous buck converter for Intel
IMVP-6/IMVP-6.5 CPUs. It can supply 25A maxi-
mum load current at up to 1.5V output with 4.5V to
28V input range. The demo board features the
LTC®3816EUHF controller. The LTC3816 is a sin-
gle-phase synchronous buck controller in a con-
stant-frequency voltage mode architecture. The con-
troller’s leading edge modulation topology allows
extremely low output voltages and supports a phase-
lockable switching frequency up to 550kHz. The
output voltage is programmed using a 7-bit VID
code. The default VID jumpers (VID6 to VID0) are
set to be 0110000 for 0.9V output. The LTC3816
features all of the IMVP-6/IMVP-6.5 requirements,
including start-up to a preset boot voltage, differen-
tial remote output voltage sensing with programma-
ble active voltage positioning, Imon output current
reporting, power optimization during sleep state, and
slow slew rate sleep state exit. Fault protection fea-
tures include input undervoltage lockout, cycle-by-
cycle current limit, output overvoltage protection,
and power-good (PWRGD) and overtemperature
flags. The LTC3816 supports wide input range (4.5V
to 36V) with optional line feedforward compensation,
temperature compensated inductor DCR or sense
resistor output current monitoring. The LTC3816
can provide high efficiency, high power density and versatile power solutions for embedded computing,
mobile computers, internet devices and navigation
displays. The controller is available in 38-pin ther-
mally enhanced eTSSOP and 5mm × 7mm QFN
packages.
The VRON pin (JP15) provides enable feature. To
shut down the converter, one simple way is to force
the VRON pin below 0.65V (JP15: OFF). Use JP19
jumper to select pulse-skipping or forced continuous
mode operation. Switching frequency is pre-set at
about 400KHz, and it can be easily modified from
150KHz to 550KHz. JP20~JP26 (VID0~VID7) are
used to set the output voltage based on the IMVP-
6/IMVP-6.5 VID code, as shown in table 2. JP1 and
JP18 are used to select either IMVP6 or IMVP6.5
specification. For detailed information, please see
LTC3816 data sheet and Intel IMVP-6/IMVP-6.5 spe-
cification.
Design files for this circuit board are available. Call
the LTC factory.
DEMO CIRCUIT 1672A
QUICK START GUIDE
LTC3816EUHF
HIGH EFFICIENCY SINGLE PHASE BUCK CONVERTER
FOR INTEL IMVP-6/IMVP-6.5 CPUs
Table 1.
Performance Summary (T
A
= 25°C)
PARAMETER CONDITION VALUE
Input Voltage Range 4.5V to 28V
Output Voltage, V
OUT
V
IN
= 4.5-28V, I
OUT
= 0A to 23A, VID6-0=0110000 0.9V ±1.5%
Maximum Output Current, I
OUT
V
IN
= 4.5-28V, V
OUTMAX
= 1.5V 25A
Typical Efficiency V
IN
= 12V, V
OUT
= 1.5V, I
OUT
= 23A
86.7%
Typical Switching Frequency 400kHz