DC1128A - Demo Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1128
2.25MHZ DUAL-OUTPUT, 600MA, MONOLITHIC STEP-DOWN DC/DC REGULATOR
LTC3419EDD
DESCRIPTION
Demonstration circuit 1128A is a Dual channel Synchronous, 2.25MHz Step-Down DC/DC Regulator featuring the LTC3419. The DC1128A has an input voltage range of 2.5V to 5.5V. Both jumper selectable
3.3V/2.5V and 1.2V/1.5V/1.8V output are capable of
delivering up to 600mA of output current. In Burst
Mode operation, the LTC3419 requires only 40uA
of quiescent current. As a result, the DC1128A provides good efficiency at light load currents. In Pulse
Skip mode, the DC1128A provides lower output ripple
voltage at light load currents than in Burst Mode. In
either mode, the DC1128A can provide up to 95%
efficiency and consumes less than 1uA in shutdown.
The LTC3419 comes in a small 10-Pin DFN package,
which has an exposed pad on the bottom-side of the
IC for good thermal performance. These features,
plus the nominal operating frequency of 2.25MHz (allowing the exclusive use of low profile surface mount
components), make the DC1128A demo board an
ideal reference circuit for battery-powered, hand-held
applications.
Design files for this circuit board are available. Call
the LTC factory.
LTC is a trademark of Linear Technology Corporation
Table 1. Performance Summary (TA = 25°C)
PARAMETER
Minimum Input Voltage
CONDITION
Maximum Input Voltage
VALUE
2.5V
5.5V
1.2V ±2%
Output Voltage VOUT1
VIN = 2.5V to 5.5V, IOUT1 = 0A to 600mA
1.5V ±2%
1.8V ±2%
Typical Output Ripple VOUT1
Output Regulation
VIN = 5V, IOUT1 = 600mA (20MHz BW)
20mVP–P
Line
±1%
Load
±1%
3.3V ±2%
Output Voltage VOUT2
VIN = 2.5V to 5.5V, IOUT2 = 0A to 600mA
Typical Output Ripple VOUT2
VIN = 5V, IOUT2 = 600mA (20MHz BW)
20mVP–P
Line
±1%
Load
±1%
Output Regulation
Nominal Switching Frequency
2.5V ±2%
2.25MHz
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1128
2.25MHZ DUAL-OUTPUT, 600MA, MONOLITHIC STEP-DOWN DC/DC REGULATOR
QUICK START PROCEDURE
Demonstration circuit 1128 is easy to set up to evaluate the performance of the LTC3419. Refer to Figure 1
for proper measurement equipment setup and follow
the procedure below.
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 Vin or Vout and GND terminals. See Figure
2 for proper scope probe technique.
1.
2.
Connect the input power supply to the Vin and
GND terminals on the left-side of the board. Connect the loads between the Vout and GND terminals on the right-side of the board. Refer to Figure
1 for the proper measurement equipment setup.
Before proceeding to operation, insert jumpers JP1
and JP2 into the OFF positions, jumper JP3 into
the Vout1 voltage position of choice (1.2V, 1.5V,
and 1.8V), and jumper JP4 into the desired mode
of operation: Pulse Skip or Burst Mode.
3.
Apply 4.0V at Vin. Measure both Vouts; they
should read 0V. The supply current will be less
than 1uA in shutdown mode.
4.
Select Vout2 of 3.3V/2.5V by place one jumper at
JP8 or JP7.
5.
Select Vout1 of 1.8V/1.5V/1.2V by place one
jumper at JP6 or JP5 or JP4.
6.
Turn on Vout1 and Vout2 by changing jumpers JP1
and JP2 from the OFF position(s) to the ON position(s). The burst mode input current should be
less than 115uA* in burst mode when input is at
4.0V. Vary the input voltage from 3.5V to 5.5V and
adjust each load current from 0 to full load. Both
output voltages should be regulating. The regulated
error is less than 2% of rated voltage.
7.
Set the load current of outputs between 25% to
100% load range, and measure both output ripple
voltages; they should measure less than 20mV
each. The switching frequencies should be between
1.8MHz and 2.7MHz (T = 0.555 us and 0.37 us)
8.
Change Vout1 and Vout2 to other desired values.
Repeat 6-7.
9.
Set the jumper to default position after test:
JP3
Burst
Mode
JP2
ON
JP1
ON
JP8
JP6
(3.3V)
(1.8V)
Vout2
Vout1
*Note: The 115uA is due to default load on sensing resistor.
Using larger resistor value for voltage divider if less current is
desired.
2
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1128
2.25MHZ DUAL-OUTPUT, 600MA, MONOLITHIC STEP-DOWN DC/DC REGULATOR
+
Load
V
-
V
A
V
-
+
+
Load
A
Figure 1. Proper Measurement Equipment Setup
Figure 2. Scope Probe Placement for Measuring Input or Output Ripple
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1128
2.25MHZ DUAL-OUTPUT, 600MA, MONOLITHIC STEP-DOWN DC/DC REGULATOR
4
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