DC488A - Demo Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 488
HIGH EFFICIENCY, LOW NOISE, INDUCTOR-LESS STEP DOWN DC/DC CONVERTER
LTC3250-1.5
DESCRIPTION
Demonstration circuit 488 is a high efficiency, inductorless step-down converter featuring the LTC3250-1.5.
The circuit produces a fixed 1.5V output from a 3.1V to
5.5V input.
Design files for this circuit board are available. Call
the LTC factory.
Table 1. Performance Summary
PARAMETER
CONDITION
VALUE
Minimum Input Voltage
3.1V
Maximum Input Voltage
5.5V
VOUT
VIN = 3.5V to 5.5V, IOUT = 0A to 250mA
1.5V ±4%
Burst Mode Operation Output Ripple
(Not including ESR spike)
10mVP–P
Continuous Mode Output Ripple
(Not including ESR spike)
4mVP–P
Nominal Switching Frequency
1.5MHz
QUICK START PROCEDURE
Demonstration circuit 488 is set up to easily evaluate the
performance of the LTC3250-1.5 low noise charge
pump. Refer to Figure 1 for proper measurement
equipment setup, and follow the procedure outlined below:
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. Connect jumper JP1 to the ON position.
2. With power off, connect a 3.6V, 200mA power supply
to the Vin and GND terminals.
3. Turn on the power at the input. Attach desired load
(up to 250mA) from Vout to GND
4. Check for the proper output voltage. Vout = 1.44V to
1.56V.
–
+
+
–
+
–
+
+
–
–
+
LOAD
–
GND
VIN
Figure 1. Proper Measurement Equipment Setup
Figure 2. Scope Probe Placement for
Measuring Input or Output Ripple
1
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 488
HIGH EFFICIENCY, LOW NOISE, INDUCTOR-LESS STEP DOWN DC/DC CONVERTER
Cfly
1.0uF
Vin
3.1V to 5.5V
GND
E3
Cin
1.0uF
1
C1
0.1uF
ON
OFF
6
C-
C+
Vin
Vout
U1
LTC3250ES6-1.5
5
JP1
2
3
SHDN
GND
E5
3
E1
1
4
SHDN
R1
4.7M
2
Cout
4.7uF
C2
0.1uF
Vout
1.5V
< 250mA
E2 Iout _
GND
E4
Figure 3. Schematic
2
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