DC1353A - Demo Manual

DEMO CIRCUIT 1353A
LTC3601
QUICK START
GUIDE
LTC3601
1.5A, 15V, MONOLITHIC SYNCHRONOUS
STEP-DOWN REGULATOR
DESCRIPTION
Demonstration circuit 1353 is a step-down converter,
using the LTC3601 monolithic synchronous buck
regulator. The DC1353A has a maximum input voltage 15V, and is capable of delivering up to 1.5A of
output current at a minimum input voltage of 4V. The
output voltage of the DC1353A can be set as low as
0.6V, the reference voltage of the LTC3601. At low
load currents, the DC1353A operates in discontinuous
mode, and during shutdown, it consumes less than 40
uA of quiescent current. In continuous mode operation, the DC1353A is a high efficiency circuit - over
80%. The DC1353A can track another voltage with
the LTC3601 track function. Because of the high
switching frequency of the LTC3601, which is programmable up to 4 MHz, the DC1353A uses low profile surface mount components. All these features
make the DC1353A an ideal circuit for use in Lithium-Ion Battery applications and distributed power
systems. Gerber files for this circuit are available.
Call the LTC Factory.
Design files for this circuit board are available. Call the
LTC factory.
As Shipped Performance Summary
PARAMETER
CONDITIONS
VALUE
Minimum Input Voltage
4V
Maximum Input Voltage
15V
GND = Shutdown
Run/Shutdown
VIN = 4V to 15V, IOUT = 0A to 1.5A
VIN = Run
1.2V ±4% (1.152V – 1.248V)
VIN = 4V to 15V, IOUT = 0A to 1.5A
1.8V ±4% (1.728V – 1.872V)
VIN = 4.5V to 15V, IOUT = 0A to 1.5A
3.3V ±4% (3.168V – 3.432V)
Typical Output Ripple Voltage
VIN = 12V, VOUT = 1.8V, IOUT = 1.5A (20 MHz BW)
< 20mVP–P
Burst Mode
VIN = 12V, VOUT = 1.8V
< 400 mA
Nominal Switching Frequency
RT = 324k
1 MHz ± 20%
Output Voltage
Regulation
Table 1. Jumper Description
JUMPER FUNCTION
JP1
Vout Setting.
JP5
Tracking or Soft-Start (SS)
JP6
Mode: Forced Continuous Mode (FCM), Burst Mode, or External Synchronization (SYNC)
JP7
Run
JP8
Frequency
JP9
ITH: Compensation
RANGE/SETTING (DEFAULT)
1.2V
(SS) - TRACK
(FCM) – SYNC – Burst Mode
(ON) - OFF
(1 MHz) - 2 MHz
INT – (EXT)
1
LTC3601
QUICK START PROCEDURE
Demonstration Circuit 1353 is easy to set up to evaluate the performance of the LTC3601. For proper
measurement equipment configuration, set up the circuit according to the diagram in Figure 1. Before proceeding to test, insert shunts into the 1.2V position of the
output voltage header JP1, into the SS (soft-start) position of Track/SS header JP5, into the FCM (Forced Continuous Mode) position of MODE header JP6, into the OFF
position of RUN header JP7, into the 1 MHz position of
FREQ header JP8, and into the EXT position of ITH header
JP9.
Vary the input voltage from 4V to 15V and adjust the
load current from 0 to 1.5A. Vout should set the input
voltage to 15V and the output current to 1.5A. Measure the output ripple voltage; it should measure less
than 20 mVAC.
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
Vin or Vout and GND terminals. See Figure 2 for
proper scope probe measurement technique.
Change the JP6 shunt from forced continuous mode to
Burst Mode. Also set the input voltage to 12V and the
output current to any current less than 400 mA. Observe the discontinuous mode of operation at the
switch node, and measure the output ripple voltage. It
should measure less than 150 mV.
With the DC1353 set up according to the proper
measurement configuration and equipment in Figure
1, apply 6.3V at Vin (Do not hot-plug Vin or increase
Vin over the rated maximum supply voltage of 15V, or
the part may be damaged.). Measure Vout; it should
read 0V. Turn on the circuit by inserting the shunt in
header JP7 into the ON position. The output voltage
should be regulating. Measure Vout - it should measure 1.2V +/- 2% (1.176V to 1.224V).
Insert the JP7 shunt into the OFF position and move
the shunt in the 1.2V output JP1 header into any of the
two remaining output voltage option headers: 1.8V
(JP2) or 3.3V (JP3). Just as in the 1.2V Vout test, the
output voltage should read Vout +/- 2% tolerance under static line and load conditions and +/- 1% tolerance under dynamic line and load conditions (+/- 2%
total). Also, the circuit operation in discontinuous
mode will be the same.
Observe the voltage waveform at the switch pins (the
other side of the inductor from the output). Verify the
switching frequency is between 800 kHz and 1.2 MHz
(T = 1.25 us and 0.833 us), and that the switch node
waveform is rectangular in shape.
When finished, turn off the circuit by inserting the
shunt in header JP7 into the OFF position.
2
LTC3601
Figure 1. Proper Equipment Measurement Set-Up
Figure 2. Measuring Input or Output Ripple
3
LTC3601
Normal Switching Frequency & Output Ripple Voltage
Waveforms
Figure 3. Switch Node & Output Ripple Voltage Waveforms
VIN = 12V, VOUT = 1.8V, IOUT = 1.5A, FSW = 2 MHz
Trace 2: Output Ripple Voltage (20 mV/div AC)
Trace 1: Switch Voltage (10 V/div)
4
LTC3601
Load Step Response Waveform
Figure 4. Load Step Response
VIN = 12V, VOUT = 1.8V, 1.5A Load Step (0A <-> 1.5A)
Forced Continuous Mode FSW = 2 MHz
Trace 2: Output Voltage (50mV/div AC)
Trace 3: Output Current (0.5A/div)
5
LTC3601
6
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