QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 516
LOW OUTPUT VOLTAGE, SYNCHRONOUS BOOST CONVERTER
1
LTC3423 and LTC3424
DESCRIPTION
Demonstration circuit 516 is a low
output voltage, synchronous boost
converter featuring LTC3423 (DC516A-
A) or LTC3424 (DC516A-B).
The LTC3423/LTC3424 is ideal for ap-
plications that require an output
voltage between 1.5V to 2.6V from a
single alkaline or NiCd/NiMH cell. A
bias voltage of 2.7V to 5.5V is re-
quired to power the internal cir-
cuitry. The output voltage is set at
1.8V. For 1V minimum battery voltage,
the LTC3423 can provide up to 350mA,
and the LTC3424 can provide up to
600mA.
The switching frequency is set at
1MHz, which gives a good trade-off
between efficiency and size. See data
sheet for efficiency data at differ-
ent frequencies.
Design files for this circuit board
are available. Call the LTC factory.
Table 1. Performance Summary
PARAMETER CONDITION VALUE
Maximum Load Current, Min (LTC3423) V
IN
= 1V 350mA
Maximum Load Current, Min (LTC3424) V
IN
= 1V 600mA
Typical Output Ripple V
OUT
(LTC3423) V
IN
= 1V, I
OUT
= 350mA 18mV
P–P
Typical Output Ripple V
OUT
(LTC3424) V
IN
= 1V, I
OUT
= 600mA 34mV
P–P
Nominal Switching Frequency 1MHz
Typical Efficiency (LTC3423) V
IN
= 1.5V, I
OUT
= 300mA 90%
Typical Efficiency (LTC3424) V
IN
= 1.5V, I
OUT
= 600mA 85%
QUICK START PROCEDURE
Demonstration circuit 516 is easy to
set up to evaluate the performance of
the LTC3423 and LTC3424. Refer to
Figure 1 for proper measurement
equipment setup and follow the proce-
dure below:
NOTE:
When measuring the input or out-
put voltage ripple, care must be
taken to avoid a long ground lead on
the oscilloscope probe. Measure the
input or output voltage ripple by
touching the probe tip directly
across the Vin or Vout and GND termi-
nals. See Figure 2 for proper scope
probe technique.
NOTE:
The board should be connected to
the bench power supply with short,
thick wires. If long connection wires
are used, electrolytic capacitors are
recommended between VIN and GND, also
VDD and GND to damp the voltage over-
shoot during plug-in. Refer to appli-
cation note 88 for details.
1.
Place jumper JP2 in the FIXED FREQ.
position.
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 516
LOW OUTPUT VOLTAGE, SYNCHRONOUS BOOST CONVERTER
2
2.
With power off, connect the input
power supply to VIN and GND. This
voltage is less than 1.8V.
3.
With power off, connect the bias
voltage to VDD and GND. This volt-
age is between 2.7V to 5.5V.
4.
Turn on both power supplies. The
voltage applied at VDD has to be
higher than VIN and VOUT.
5.
Place jumper JP1 in the RUN posi-
tion.
6.
Check for the proper output volt-
age. Vout = 1.746V to 1.854V.
7.
Once the proper output voltage is
established, adjust the load within
the operating range and observe the
output voltage regulation, ripple
voltage, efficiency and other pa-
rameters.
+
–
+
–
+
–
+
–
+
–
LOAD
BENCH
SUPPLY
+
–
+
–
+
–
BENCH
SUPPLY
+
–
Figure 1. Proper Measurement Equipment Setup
VIN
GND
Figure 2. Scope Probe Placement for
Measuring Input or Output Ripple
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 516
LOW OUTPUT VOLTAGE, SYNCHRONOUS BOOST CONVERTER
3
Figure 3. LTC3423 Transient Response
(V
IN
=1.2V, I
OUT
from 50mA to 350mA; Top
Trace:V
OUT
, 50mV/DIV AC coupled; Bottom
Trace: I
O
, 500mA/DIV)
Figure 4. LTC3423 Transient Response
(V
IN
=1.5V, I
OUT
from 50mA to 350mA; Top
Trace:V
OUT
, 50mV/ DIV AC coupled; Bottom
Trace: I
O
, 500mA/ DIV)
Figure 5. LTC3424 Transient Response
(V
IN
=1.2V, I
OUT
from 50mA to 500mA; Top
Trace:V
OUT
, 50mV/ DIV AC coupled; Bottom
Trace: I
O
, 500mA/ DIV)
Figure 6. LTC3424 Transient Response
(V
IN
=1.5V, I
OUT
from 50mA to 500mA; Top
Trace:V
OUT
, 50mV/ DIV AC coupled; Bottom
Trace: I
O
, 500mA/ DIV)
