DC1489A - Demo Manual

DEMO C IR C U IT 14 8 9 A
LTC3619EDD/LTC3619BEDD
Q U IC K S TAR T G U IDE
L T C 3 6 19 EDD/ L T C 3 6 19 B EDD
S Y N C H R ON OU S B U C K DU AL R EG U L AT OR
W IT H ADJ U S TAB L E IN P U T C U R R EN T L IMIT
DESCRIPTION
Demonstration circuit 1489A is a synchronous buck dual
regulator w ith adjustable input current limit featuring the
LTC3619EDD/ LTC3619BEDD and is ideally suited for
pulsed load applications w here the input current needs to
be limited. The LTC3619EDD operates in burst mode for
higher light load efficiency, w hile the LTC3619BEDD operates in pulse-skip mode for low er output ripple. The
package style for the LTC3619EDD/ LTC3619BEDD is a
10 lead 3mm x 3mm plastic DFN.
Demonstration circuit 1489A is configured for 500mA
maximum input current limit. The outputs are configured
for a 3.3V / 400mA continuous current output and a 3.4V
output that can handle pulsed load currents of up to 2A,
w ith duty cycles of up to 15% . The input voltage range is
5V ±10% . The fixed input current limit can be adjusted by
replacing one resistor. Please see the datasheets for more
information.
The LTC3619/LTC3619B datasheets gives complete descriptions of these parts, operation and application information and must be read in conjunction w ith this quick
start guide for demo circuit 1489A.
Design files for this circuit board are available. Call the
LTC factory.
Table 1. Perform ance Sum m ary (TA = 25°C)
PAR AM ETER
CON DITIO N S /N O TES
Input Voltage Range VIN
Input Current Limit
Output Voltage VOUT1
Output Voltage VOUT2
Efficiency (Figures 4 and 5)
VIN
VIN
VIN
VIN
VIN
VIN
VALUE
= 4.5V to 5.5V,IOUT1 = 0A to 400mA
= 4.5V to 5.5V,IIN = 0A to 500mA
= 4.5V,IOUT1 = 400mA
= 5.5V,IOUT1 = 400mA
= 4.5V,IOUT2 = 500mA
= 5.5V,IOUT2 = 500mA
4.5V – 5.5V
500mA ± 5%
3.3V ± 3%
3.4V ± 3%
92.6% typical
92.3% typical
93.4% typical
92.6% typical
Q U ICK STA RT PROCEDU RE
Demonstration circuit 1489A is easy to set up to evaluate
the performance of the LTC3619EDD/ LTC3619BEDD.
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 or directly across the capacitor. See Figure 2 for proper
scope probe technique.
1. Place the jumper in the following position:
JP1
On
JP2
On
2. With power off, connect the input power supply to
VIN and GND.
3. Turn on the power at the input.
NOTE: Make sure that the input voltage does not exceed 5.5V.
4. Check for the proper output voltage.
VOUT1 = 3.200 to 3.400V,
V OUT2 = 3.298 to 3.502V
If there is no output, temporarily disconnect the load
to make sure that the load is not set too high.
5. Once the proper output voltages are established,
adjust the loads within the operating range and ob-
1
LTC3619EDD/LTC3619BEDD
serve the output voltage regulation, ripple voltage,
efficiency and other parameters.
+
Optional Circuit for Pulsed Loads
BNC cable to scope
10mV/A
6. The method for evaluating pulsed loads will be discussed in the next section.
VIN supply
VIN
IIN
A
+
V
-
-
Pulse Generator
0-5V +
I OUT2
I OUT1
A
+
VOUT2 Load
-
V OUT2
A
+
VOUT1
+
V
V
-
-
+
VOUT1 Load
-
Figure 1. Proper M easurem ent Equipm ent Setup
Figure 2. M easuring Input or Output R ipple Directly Across Bulk Capacitor
PU L SED L OA D TESTING
Demonstration circuit 1489A can be setup for simple
evaluation of pulse loads – please see optional circuit in
2
Figure 1 for proper setup. The circuit is capable of pulsed
load of up to 2A w ith duty cycles up to 15% on VO U T2.
LTC3619EDD/LTC3619BEDD
Starting from step 5 in the quick start procedure above,
follow the procedure below :
1. Disconnect all loads from VO U T2 as the pulse load circuitry is on board.
2. The pulsed load current is measured by connecting
J1 to the scope using a BNC cable and setting the oscilloscope to 10mV/div
3. Input current and output voltage can be measured on
an oscilloscope for evaluation.
4. A pulse generator w ith adjustable amplitude is connected betw een IOSTEP CLK and GND as indicated in
Figure 1. The pulse generator should be capable of
generating up to 5V pulses. Adjust the period and
duty cycle of this signal to match that of the required
load prior to attaching the pulse generator.
5. Adjust pulse generator amplitude until the required
load current is achieved as measured on J1
(10mV/A).
6. An example result show ing VO U T2, IIN and a pulse load
IO UT2 is given in Figure 3.
Vout2 (100mV/div AC coupled)
Iin (200mA/div)
Iout2 (1A/div)
(IOSTEP at 10mV/div)
Figure 3. Pulse Load W aveform s for 2A pulsed load, 1/8th duty cycle, 4.6m s period
A DJ U STING INPU T CU RRENT L IM IT
It is possible to modify the demonstration circuit for either higher or low er input current limits. This is accomplished by changing resistor R9 to the required value as
suggested in the LTC3619EDD/ LTC3619BEDD data-
sheets. Note that for these different current values, the
inductor may not be optimum and may have to be
changed as w ell. Please refer to the datasheet for more
information.
3
LTC3619EDD/LTC3619BEDD
Figure 4. Typical Efficiency vs. Load Current, CH1, 3.3Vout for A-A and A-B boards
4
LTC3619EDD/LTC3619BEDD
M aximum output current is input current limited
M aximum output current is input current limited
Figure 5. Typical Efficiency vs. Load Current, CH2, 3.4Vout for A-A and A-B boards
5
GND
VOUT2
3.4V / 2A
Pulsed
Load
PGOOD2
RUN2
GND
E9
E7
E5
E3
1000K
R3
E2
COUT3
2200uF
6.3V
R12
0.01
1
CIN2
10uF
6.3V
COUT4
2200uF
6.3V
R2
200K
R13
(OPT)
R11 51
R10 10K
1
E11
OFF
E12
GND
J1
10mV / A
IOSTEP CLK
C1
(OPT)
10
7
8
9
**
R7
215K
1%
L2 1.5uH
JP2
RUN2
ON
2
R5
COUT7 1000K
(OPT) 1%
DYNAMIC LOAD CIRCUIT
COUT2
4.7uF
6.3V
CIN1*
68uF
6.3V
Q1
SUD50N03-10CP-E3
VOUT2
VOUT2
COUT1
(OPT)
3
2
1
3
-B
LTC3619BEDD
LTC3619EDD
-A
L1
R8
221K
1%
3.3uH
C3
2200pF
1
5
4
2
U1
R9
110K
1%
Vfb1
SW1
PGOOD1
Run1
ASSY
Vfb2
SW2
PGOOD2
Run2
U1* *
6
Vin
11 G ND
VIN
E1
4.5V - 5.5V
Up to 500mA
2
3
4
5
R lim
3
6
R6
1000K
1%
OFF
ON
JP1
RUN1
C2
10pF
2
1
3
* FOR DEMO BOARD USE ONLY
COUT6
(OPT)
R1
200K
COUT5
4.7uF
6.3V
E10
E8
E6
E4
1000K
R4
GND
VOUT1
3.3V / 400mA
PGOOD1
RUN1
LTC3619EDD/LTC3619BEDD
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