DC970A - Demo Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 970A
HIGH EFFICIENCY, 500MA BUCK PLUS 300MA VLDO REGULATOR
LTC3541EDD/LTC3541EDD-1
DESCRIPTION
DC970A-A/B featuring the LTC3541/LTC3541-1 provides a high efficiency, 500mA synchronous buck
plus 300mA VLDO regulator. The DC970A has an input voltage range of 3.0V to 5.5V. The jumper selectable 2.5V/1.8V output is capable of delivering up to
500mA of output current; the jumper selectable
0.8V/1.2V/1.5V/1.8V output is capable of delivering
up to 300mA of current. The synchronous buck converter provides a high efficiency output, typically 90%
while switching at 2.25MHz, allowing the use of small
surface mount inductor and capacitors. In Burst
Mode operation, the LTC3541 /LTC3541-1’s low quiescent current results in high efficiency at light load
currents. In Pulse Skip mode, the DC970A provides
lower output ripple voltage at light load currents than
in Burst Mode. In either mode, the DC970A can provide up to 95% efficiency and consumes less than
3uA in shutdown. The LTC3541 comes in a small 10Pin DFN package, which has an exposed pad on the
bottom-side of the IC for good thermal performance.
These features make the DC970 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
DC970A-A
CONDITION
Buck output Vout1 rise ahead of LDO Vout2
VALUE
IC: LTC3541
DC970A-B
LDO output Vout2 rise ahead of Buck Vout1
IC: LTC3541-1
Input Voltage range
VIN • Vout2 + 1.4V
3V-5.5V
Output Voltage VOUT1
VIN = 3V to 5.5V, IOUT1 = 0A to 500mA
1.8V / 2.5V ±2%
Typical Output Ripple VOUT1
VIN = 4.5V, IOUT1= 500mA (20MHz BW)
20mVP–P
0.8V ±2%
Output Voltage VOUT2
VIN = 3V to 5.5V, IOUT2 = 0A to 300mA
1.2V ±2%
1.5V ±2%
1.8V ±2%
Typical Output Ripple VOUT2
Nominal Switching Frequency
VIN = 4.5V, IOUT2 = 300mA (20MHz BW)
10mVP–P
2.25MHz
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 970A
HIGH EFFICIENCY, 500MA BUCK PLUS 300MA VLDO REGULATOR
QUICK START PROCEDURE
Demonstration circuit 970A is easy to set up to evaluate the performance of the LTC3541. Refer to Figure 1
for proper measurement equipment setup and follow
the procedure below.
4.
Set JP9 in VOUT1 position. In some rare applications,
if external input for VLDO is desired, set JP9 to
LVIN_EXT. Check datasheet for more detailed usage of external input for VLDO.
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.
5.
Apply 3.3V at Vin. Measure both Vouts; they
should read 0V. The supply current will be less
than 3uA in shutdown condition.
6.
Turn on Vout1 and Vout2 by changing jumpers JP5
and JP7 from the OFF position(s) to the ON position(s). Vary the input voltage from 3V to 5.5V and
check output voltage. Both output voltages should
be regulating. The regulated error should be less
than 2% of rated voltage. In non load burst mode
with both Buck (Vout1) and VLDO (Vout2) enabled
the input current should be less than 70uA.
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. Please note, the maximum load on Vout1 is
500mA minus load on Vout2. The switching frequencies should be between 1.8MHz and 2.7MHz.
8.
Jumper default position: (total of 6 jumpers
needed)
1.
2.
Connect the input power supply to the Vin and
GND terminals on the left-side of the board. Do
not hot-plug Vin or increase Vin over the rated
maximum supply voltage of 5.5V. 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.
Minimum operating VIN voltage required for VLDO
regulator and linear regulator regulation is:
VIN • Vout2 + 1.4V and VIN • 3.0V.
3.
Before proceeding to operation, insert jumpers JP5
and JP7 into the OFF positions, jumper JP1-JP4
into the Vout2 voltage position of choice (0.8V,
1.2V, 1.5V, and 1.8V), jumper JP8 into the Vout1
voltage position of choice (1.8V and 2.5V) and
jumper JP6 into the desired mode of operation:
Pulse Skip or Burst Mode.
JP9
JP8
JP7
JP6
JP5
JP1JP4
Vout1
1.8V
ON
BURST ON
1.2V
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 970A
HIGH EFFICIENCY, 500MA BUCK PLUS 300MA VLDO REGULATOR
-
V
Load
+
A
V
V
+
+
-
Power
supply
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 970A
HIGH EFFICIENCY, 500MA BUCK PLUS 300MA VLDO REGULATOR
4
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