Linear Technology LTC3718 User manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 464
DDR, HSTL, STTL TERMINATION POWER SUPPLY
LTC3718
DESCRIPTION
Demonstration circuit 464 is a termination power supply
that sinks or sources up to 12A current. Typical applica-
tions include termination power supplies for DDR or
QDR memories. DC464 utilizes the LTC3718, a constant
on-time, valley current mode synchronous buck control-
ler with an integrated monolithic boost switcher that
produces 5V bias for driving logic level MOSFETs. The
demo circuit provides additional footprints for paralleling
more MOSFETs and input/output capacitors for higher
current applications. The output voltage (V
OUT
) equals
half of the reference voltage (V
REF
). The default refer-
ence voltage is the input voltage, V
IN
. An external refer-
ence can be provided to program the output voltage di-
rectly.
SPECIFICATIONS
• V
IN
2.5V typical, 1.5V–5V
• V
OUT
V
IN
/2
• I
OUT
± 10A continuous, ± 12A
MAX
with air flow at
100LFM
SETUP NOTES
JUMPER SETTINGS
JP1: BOOST at ON position
JP2: VIN2 at ON position
EXTERNAL REFERENCE
The output of this demo board can be programmed by
the external reference at the VREF pin.
NOTE: R4 must be removed before applying V
REF
.
QUICK START PROCEDURE
Refer to Figure 1 and Figure 2 for proper measurement
equipment setup and follow the procedure below:
1. Connect the input 2.5V power source to the VIN and
GND pins using wires capable of handling 6A current.
2. Turn on the input power supply. VOUT should read
about V
IN
/2 ± 0.05V. If V
IN
is fixed at 2.5V, V
OUT
=1.25V ± 0.05V
SOURCING CURRENT TEST (FIGURE 1)
3. Turn off the input power supply VIN first.
4. Connect the load to the VOUT and GND pins with the
positive terminal of the load connecting to VOUT.
5. Turn on VIN.
6. Increase the load current to 10A. V
OUT
should always
equal to V
IN
/2 ± 0.05V. If V
IN
is fixed at 2.5V, V
OUT
should read about 1.25V
± 0.05V.
SINKING CURRENT TEST (FIGURE 2)
7. Turn off the input power supply VIN first.
8. Connect the load to the VIN and VOUT pins with the
positive terminal of the load connecting to VIN and
the negative terminal of load connecting to VOUT.
9. Turn on VIN.
10. Increase the load current to 10A. If VREF is fixed at
2.5V, VOUT should read about 1.25V
± 0.05V.
1

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 464
DDR, HSTL, STTL TERMINATION POWER SUPPLY
+
–
LOAD
+
–
–
+
+
–
+–
I
OUT
I
IN
V
IN
(1.5V–5V)
+–
Figure 1. Proper Measurement Equipment Setup for Output Sourcing Current
_
+
+
–+
–
+–
LOAD
+
–
I
IN
I
OUT
V
IN
(1.5V–5V)
+–
Figure 2. Proper Measurement Equipment Setup for Output Sinking Current
2