DEMO MANUAL DC1596A
LTC3607EUD
Dual 600mA 15V Monolithic
Synchronous Step-Down Regulator
DESCRIPTION
Demonstration circuit DC1596 is a dual output regulator
consisting of two constant-frequency step-down convert-
ers, based on the
LTC
®
3607
monolithic dual channel
synchronous buck regulator. The DC1596 has an input
voltage range of 4.5V to 15V, with each regulator capable of
delivering up to 600mA of output current. The DC1596 can
operate in either Burst Mode
®
operation or pulse-skipping
mode. In shutdown, the DC1596 quiescent current is less
than 1µA. The DC1596 is a very efficient circuit attaining
up to 90%. The DC1596 uses the LTC3607’s16-lead QFN
package, which has an exposed pad on the bottom side
of the IC for better thermal performance. These features,
plus a set operating frequency range of 2.25MHz, make
the DC1596 demo board an ideal circuit for industrial or
distributed power applications.
Design files for this circuit board are available at
http://www.linear.com/demo
L,
LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners.
PERFORMANCE SUMMARY
PARAMETER
Minimum Input Voltage
Maximum Input Voltage
Run
Output Voltage V
OUT1
Regulation
Typical Output Ripple V
OUT1
Output Voltage V
OUT2
Regulation
Typical Output Ripple V
OUT2
Mode Setting
Burst Mode Operation Output Current Thresholds
Pulse-Skipping Operation Output Current
Thresholds
Switching Frequency
Specifications are at T
A
= 25°C
VALUE
4.5V
15V
CONDITIONS
RUN Pin = GND
RUN Pin = V
IN
V
IN1
= 4.5V to 15V, I
OUT1
= 0A to 600mA
V
IN1
= 12V, I
OUT1
= 600mA (20MHz BW)
V
IN2
= 4.5V to 15V, I
OUT2
= 0A to 600mA
V
IN2
= 12V, I
OUT2
= 600mA (20MHz BW)
Mode Pin Floating
Mode Pin Grounded
Channel 1: PV
IN1
= 12V, V
OUT1
= 1.8V
Channel 2: PV
IN2
= 12V, V
OUT2
= 3.3V
Channel 1: PV
IN1
= 12V, V
OUT1
= 1.8V
Channel 2: PV
IN2
= 12V, V
OUT2
= 3.3V
Shutdown
Operating
1.2V ±4% (1.152V-1.148V)
1.5V ±4% (1.44V-1.56V)
1.8V ±4% (1.728V-1.872V)
<20mV
P-P
2.5V ±4% (2.425V-2.6V)
3.3V ±4% (3.168V-3.432V)
5V ±4% (4.8V-5.2V)
<20mV
P-P
Burst Mode Operation
Pulse-Skipping
I
OUT1
< 480mA
I
OUT2
< 360mA
I
OUT1
< 330mA
I
OUT2
< 240mA
2.25MHz ±20%
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DEMO MANUAL DC1596A
QUICK START PROCEDURE
The DC1596 is easy to set up to evaluate the performance
of the LTC3607. For a proper measurement equipment
configuration, set up the circuit according to the diagram
in Figure 1.
Note:
When measuring the input or output 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 V
IN
or V
OUT
and GND terminals. See the proper scope probe
technique in Figure 2.
Please follow the procedure outlined below for proper
operation.
1. Connect the input power supply to the PVIN1/PVIN2 and
GND terminals (V
IN1
and V
IN2
are separate nodes but
are connected). Connect the loads between the VOUT
and GND terminals. Refer to Figure 1 for the proper
measurement equipment setup.
Before proceeding to operation, insert jumper shunts
XJP1 and XJP2 into the OFF positions of headers JP1
and JP2, shunt XJP3 into the pulse-skip position of
MODE header JP3, and shunt XJP4 into the VOUT1
voltage options of choice of header JP4: 1.2V, 1.5V, or
1.8V, and shunt XJP5 into the VOUT2 voltage options
of choice of header JP5: 2.5V, 3.3V, or 5V.
2. Apply 5.5V at PVINs 1, 2. Measure both VOUTs; they
should read 0V. If desired, one can measure the shut-
down supply current at this point. The supply current
will be less than 1µA in shutdown.
3. Turn on VOUT1 and VOUT2 by shifting shunts XJP1
and XJP2 from the OFF positions to the ON positions.
Both output voltages should be within a tolerance of
±2%.
4. Vary the input voltages from 5.8V (the minimum V
IN
is
dependent on V
OUT
) to 15V, and the load currents from
0A to 600mA. Both output voltages should be within
±4% tolerance.
5. Set the load current of both outputs to 600mA and the
input voltages to 12V, and then measure each output
ripple voltage (refer to Figure 2 for proper measure-
ment technique); they should each measure less than
20mVAC. Also, observe the voltage waveform at either
switch node (Pin 5 for reg.1 and Pin 8 for reg.2) of each
regulator. The switching frequencies should be about
2.25MHz ±20% (T = 555ns and 370ns). Both switch
node waveforms should be rectangular in shape, and
180° out-of-phase with each other.
6. To operate the ckt.s in Burst Mode operation, change
the shunt position of header JP3 to BURST MODE.
7. Regulators 1 (PVIN1) and 2 (PVIN2) are completely
separated from each other; thus, they can be powered
from different individual input supplies (if R11 is re-
moved), as can the signal input supply, SVIN. However,
SVIN must powered for either regulator to function
(SVIN is connected to PVIN1 through a filter on the
demo board.).
8. When finished, insert shunts XJP1 and XJP2 to the OFF
position(s) and disconnect the power.
Warning:
If the power for the demo board is carried in
long leads, the input voltage at the part could “ring”, which
could affect the operation of the circuit or even exceed the
maximum voltage rating of the IC. To eliminate the ring-
ing, a small tantalum capacitor (for instance, AVX part #
TPSY226M035R0200) is inserted on the pads between
the input power and return terminals on the bottom of the
demo board. The (greater) ESR of the tantalum capacitor
will dampen the (possible) ringing voltage caused by the
long input leads. On a normal, typical PCB, with short
traces, this capacitor is not needed.
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