DC1389A - Demo Manual

QUICK START GUIDE FOR DEMONSTRATION
CIRCUIT 1389A
1389A
DEMO CIRCUIT
QUICK START GUIDE
LTC3521EUF
Synchronous 1A Buck-Boost DC/DC Converter and
Dual 600mA Buck DC/DC Converters
DESCRIPTION
Demonstration circuit 1389A is high efficiency triple output DC/DC power supply featuring the LTC3521. The IC
includes a 4-switch synchronous Buck-Boost DC/DC
converter with 1A switch ratings and two synchronous
600mA Buck converters. The board will accept an input
voltage between 2.4V and 5V, and provide fixed output
voltages of 3.3V @800mA for the Buck-Boost converter
and 1.2V & 1.8V @600mA for the Buck converters.
The board includes jumpers for shutdown for each converter, one jumper for PWM or BURST operation and
terminals to monitor each converter’s Power Good output signal. Other features are; 1µA shutdown current,
integrated soft start, thermal and over current protection,
under voltage lockout, 100% duty cycle for the Buck
converter and a 1MHz switching frequency that allows
small L and C components to be used.
With BURST mode selected, the buck converters operate
in BURST mode at low load current and automatically
switch to PWM mode at higher loads. The Buck-Boost
converter will also operate in burst mode but the available load current is reduced considerably, to approximately 50mA. No load BURST mode quiescent current is
approximately 50µA. When all three converters are shutdown, the quiescent current drops to less than 1µA.
The Power Good output terminals pull low if the output
voltage is 8% or more below the regulation voltage.
The LTC3521 datasheet gives a complete description of
the part, operation and application information. The datasheet must be read in conjunction with this quick start
guide.
Design files for this circuit board are available. Call
the LTC factory.
, LTC and LT are registered trademarks of Linear Technology Corporation. ThinSOT and
PowerPath are trademarks of Linear Technology Corporation.
Performance Summary ( TA = 25oC )
PARAMETER
Input Voltage Range
Buck-Boost Output Voltage (Vout 1)
Buck Output Voltage (Vout 2)
Buck Output Voltage (Vout 3)
Maximum Output Current (Buck-Boost)
Maximum Output Current (Buck)
Input Supply Current
Input Supply Current (no load)
Input Supply Current (no load)
CONDITION
Vin = 2.4V, Vout Load = 100mA
Vin = 2.4V, Vout Load = 100mA
Vin = 2.4V, Vout Load = 100mA
Vin = 2.4V, PWM mode
Vin = 2.4V
All Converters Shutdown, Vin = 2.4V
All Converters Enabled, BURST Mode, Vin = 2.4V, No Load
All Converters Enabled, PWM Mode, Vin = 2.4V, No Load
VALUE
2.4V to 5V
3.3V +/- 2.5%
1.2V +/- 2.5%
1.8V +/- 2.5%
800mA
600mA
<1µA
50µA, typ.
8.5mA, typ.
Table 1. Circuit Specifications
QUICK START PROCEDURE
This Demonstration circuit 1389A can be evaluated using the setup
shown in Figure 1.
1. Place all Shutdown jumpers in the ON position and the
MODE jumper to the PWM position.
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1389A
2. With AC power off, connect the input power supply to Vin and
GND.
current is limited to approximately 50mA if the Mode jumper is
set for BURST.
3. Connect voltmeters to Vin and ground terminals and each
Vout and Ground terminals.
8. 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.
4. With the input voltage turned down, switch on the input power
supply and raise the input voltage to 1.8V.
5. Verify that each output voltage meets the values as shown in
Table 1.
9. The Power Good terminals can be monitored with a voltmeter
or an oscilloscope. The Power Good outputs pull low if the
output voltage is 8% or more below the regulation voltage,
otherwise they are pulled up to their respective output voltage
through a 1MΩ pull-up resistor.
6. Increase the input voltage to 2.5V and connect suitable load
resistors between each output and ground.
7. Verify each output voltage. If an output is low, temporarily disconnect the load to make sure that the load current is not set
too high. Also, monitor the input voltage at the board terminals
to verify that the input voltage has not dropped due to the increased input current. Note: The Buck-Boost converter output
Shutdown
Power
Supply
10. To measure no load input current, connect a mA/µA meter in
series with the input supply, adjust for 2.4V and read meter.
Both BURST and PWM quiescent current can be verified by
moving JP1 to the appropriate position.
Power
Mode Good
Outputs
+
+
RL2 Vout2
+
RL2 Vout3
+
-
RL1
Vout1
Figure 1. Proper Measurement Equipment Setup
Figure 2. Measuring Input or Output Voltage Ripple
2
PGOOD3
PGOOD2
PGOOD1
GND
VOUT1
3.3V / 1A
GND
E11
E10
E9
E4
E3
E2
VOUT1
CIN1
47uF
10V
PGOOD3
PGOOD2
PGOOD1
C8
0.1uF
+
OFF
ON
OFF
ON
OFF
ON
JP4
SHDN3
JP3
3
2
1
3
2
SHDN2
1
JP2
3
2
SHDN1
1
C3
22uF
6.3V
1206
R5
221K
1%
R4
1.00M
1%
8
C10
(Opt)
C9
(Opt)
16
14
2
3
4.7uH
CDRH5D16NP-4R7NC
Sumida
PGOOD3
PGOOD2
4
9
1
10
CIN4
4.7uF
10V
15
R3
1M
R2
1M
PGOOD1
CIN3
4.7uF
10V
1M
VOUT3
L1
VOUT2
VOUT1
R1
CIN2
4.7uF
10V
F B1
V O UT1
SW1B
SW1A
P G O O D3
P G O O D2
P G O O D1
SH DN 3
SH DN 2
SH DN 1
GND
25
5
VIN
GND
6
11
PVIN1
21
PGND1A
22
PVIN2
PGND1B
12
E1
F B3
SW3
F B2
SW2
23
17
24
20
7
CDRH2D18/HP-3R3NC
Sumida
L3
3.3uH
CDRH2D18/HP-3R3NC
Sumida
L2
3.3uH
U1
LTC3521EUF
P WM
PGND2
18
VIN
2.4V - 5V
C5
10uF
6.3V
0805
C2
10uF
6.3V
0805
VIN
JP1
MODE
C4
22pF
VOUT3
C1
22pF
VOUT2
3
2
1
R9
100K
1%
R8
102K
1%
R7
68.1K
1%
R6
137K
1%
BURST
PWM
C7
0.1uF
C6
0.1uF
E8
E7
E6
E5
GND
VOUT3
1.2V / 600mA
GND
VOUT2
1.8V / 600mA
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1389A
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