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dc1839af

DEMO MANUAL DC1839A

QUICK START PROCEDURE

The DC1839A is easy to set up to evaluate the performance 
of the LTC3634. For a proper measurement equipment 
configuration, set up the circuit according to the diagram 
in Figure 1.

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 V

IN

 

or V

OUT

 and GND terminals. See the proper scope probe 

technique in Figure 2.

Please follow the procedure outlined below for proper 
operation.

1. Connect the input power supply to the V

IN

 and GND 

terminals. Connect the loads between the V

OUT

 and GND 

terminals. Refer to Figure 1 for the proper measurement 
equipment setup.

  Before proceeding to operation, insert jumper shunts 

XJP1 and XJP2 into the OFF positions of headers JP1 
and JP2, shunt XJP3 into the forced continuous mode 
(FCM) position of MODE header JP3, shunt XJP4 into 
the 180° (out-of-phase) position of PHASE header JP4, 
shunt XJP5 into the soft-start positions of TRACK/SS 
header JP5, and shunt XJP6 into the V

OUT1

 voltage 

options of choice of header JP6: 1.2V, 1.5V, or 1.8V. 

2.  Apply 5V at V

IN

. Measure both V

OUT

s; they should read 

0V. If desired, one can measure the shutdown supply 
current at this point. The supply current should be less 
than 30μA in shutdown. 

3.  Turn on V

OUT1

, V

DDQ

, and V

OUT2

, V

TT

, by shifting shunts 

XJP1 and XJP2 from the OFF positions to the ON posi-
tions. Both output voltages should be within a tolerance 
of ±1%.

4. Vary the input voltage from 3.6V to 15V, the channel 1 

load current from 0 to 3A, and the channel 2 load cur-
rent from 0 to ±3A (The V

TT

 channel sinks as well as 

sources current. An easy way to test this capability is 
shown in the test set-up diagram; connect a variable 

resistor from V

IN

 to V

OUT

, along with an ampmeter. The 

current will be V

IN

 minus V

OUT

 divided by the variable 

resistor value). V

DDQ

 output voltage tolerance should 

be within ±2%, whereas the output voltage tolerance 
of V

TT

 should be within ±3%.

5.  Set the load current of both outputs to 3A and the input 

voltage to 12V, then measure each output ripple voltage 
(refer to Figure 2 for proper measurement technique); 
they should each measure less than 20mVAC. Also, 
observe the voltage waveform at either switch node 
(pins 16 and 17 for channel 1, and 23 and 24 for chan-
nel 2) of each regulator. (Both switch node waveforms 
should be rectangular in shape and 180°out-of-phase 
with each other). The switching frequencies should be 
between 800kHz and 1.2MHz (T = 1.25μs and 0.833μs).

6.  With the board under proper operation, observe the load 

regulation, efficiency, in-phase operation (by changing 
jumper XJP4 to the 90° position), or Burst Mode op-
eration (by changing jumper XJP3 to the Burst Mode 
position).

7. (Optional) Moving the zero ohm resistor at RV

DDQ

inserting it into R

DDQIN

, and applying a voltage to turret 

V

DDQIN

 allows channel 2 output voltage (VTTR) to be 

adjusted to any desired voltage (to one-half the voltage 
at VDDQIN).

When finished, insert shunts XJP1 and XJP2 to the OFF 
position(s) and disconnect the power.

Warning: If the power for the demo board is carried in 
long leads, the input voltage at the part could ring, which 
could affect the operation of the circuit or even exceed 
the maximum voltage rating of the IC. To eliminate the 
ringing, a small Poscap capacitor (for instance, AVX part 
number TPSY226M035R0200) is inserted on the pads 
between the input power and return terminals on the bot-
tom of the demo board. The (greater) ESR of the Poscap 
will dampen the (possible) ringing voltage due to the use 
of long input leads. On a normal, typical PCB, with short 
traces, this capacitor is not needed.

Summary of Contents for DC1839A

Page 1: ...wners PERFORMANCE SUMMARY forced continuous mode In Burst Mode operation which isthepreferredmodeoflowloadcurrentoperation theDC supply current is typically only 1 3mA both channels at no load sleep m...

Page 2: ...hown in the test set up diagram connect a variable resistor from VIN to VOUT along with an ampmeter The current will be VIN minus VOUT divided by the variable resistor value VDDQ output voltage tolera...

Page 3: ...3 dc1839af DEMO MANUAL DC1839A VS VARIABLE RESISTOR QUICK START PROCEDURE Figure 1 Proper Measurement Equipment Setup...

Page 4: ...LTC3634 DC1839A Efficiency Figure 2 Measuring Input or Output Ripple GND VIN LOAD CURRENT A 0 EFFICIENCY 100 10 90 70 50 30 80 60 40 20 0 dc1839a F03 3 0 1 5 2 5 1 0 2 0 0 5 VIN 12V VDDQ 2 5V VTT 1 25...

Page 5: ...0pF TRACE 3 OUTPUT VOLTAGE 50mV DIV AC TRACE 4 OUTPUT CURRENT 1A DIV dc1839a F04 VIN 12V VTT 0 9V 3A LOAD STEP 3A TO 3A FORCED CONTINUOUS MODE fSW 1MHz EXTERNAL COMPENSATION RITH2 15k CITH2 1000pF TRA...

Page 6: ...Board Circuit Components 1 0 CC1 CC2 OPTION CAP 0402 10pF 5 25V NPO NIC NMC0402NPO100J25TRPF 2 0 CDDQIN OPTION CAP 0805 10 F 10 6 3V X5R OPTION NIC NMC0805X5R106K6 3TRPLP3KF 3 0 CIN3 CIN4 OPTION CAP 1...

Page 7: ...GNIFICANTLY AFFECT CIRCUIT PERFORMANCE OR RELIABILITY CONTACT LINEAR TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND SCHEMATIC SUPPLIED FOR USE...

Page 8: ...DING ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE EXCEPT TO THE EXTENT OF THIS INDEMNITY NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR ANY INDIRECT SPECIAL INCIDENTAL OR CONS...

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