DC734A - Demo Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 734
DUAL SYNCHRONOUS, 800MA, 2.25 MHZ STEP-DOWN DC/DC REGULATOR
LTC3407-2
DESCRIPTION
Demonstration circuit 734 is a Dual Synchronous,
800mA, 2.25MHz Step-Down DC/DC Regulator featuring the LTC 3407-2. The DC734 has an input
voltage range of 2.5V to 5.5V, and either output is
capable of delivering up to 800mA of output current.
In Burst Mode operation, the LTC3407-2 requires
only 40uA of quiescent current, and the DC734 provides higher efficiency at light load currents. In Pulse
Skip mode, the DC734 provides lower output ripple
voltage at light load currents. In either mode, the
DC734 can provide up to 96% efficiency on either
channel and consumes less than 1uA in shutdown.
The LTC3407-2 comes in a small 10-Pin DFN package, which has an exposed pad on the bottom-side of
the IC for better thermal performance. These features,
plus the nominal operating frequency of 2.25MHz (allowing the exclusive use of low profile surface mount
components), make the DC734 demo board an ideal
circuit for use in 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
Minimum Input Voltage
CONDITION
Maximum Input Voltage
VALUE
2.5V
5.5V
1.2V ±2%
Output Voltage VOUT1
VIN = 2.5V to 5.5V, IOUT1 = 0A to 800mA
1.5V ±2%
1.8V ±2%
Typical Output Ripple VOUT1
VIN = 5V, IOUT1 = 800mA (20MHz BW)
20mVP–P
Line
±1%
Load
±1%
Output Voltage VOUT2
VIN = 2.5V to 5.5V, IOUT2 = 0A to 800mA
2.5V ±2%
Typical Output Ripple VOUT2
VIN = 5V, IOUT2 = 800mA (20MHz BW)
20mVP–P
Line
±1%
Load
±1%
Output Regulation
Output Regulation
Nominal Switching Frequency
2.25MHz
1
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 734
DUAL SYNCHRONOUS, 800MA, 2.25 MHZ STEP-DOWN DC/DC REGULATOR
QUICK START PROCEDURE
Demonstration circuit 734 is easy to set up to evaluate the performance of the LTC3407-2. 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. See Figure
2. for proper scope probe technique.
Note: Capacitor C5 is an optional part. It was inserted on the DC734 to dampen the (possible) ringing
voltage due to the use of long input leads. On a normal, typical PCB, with short traces, the capacitor is
not needed.
1.
2.
3.
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, or the part may
be damaged. 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.
Before proceeding to operation, insert jumpers JP1
and JP2 into the OFF positions, jumper JP3 into
the Vout1 voltage position of choice (1.2V, 1.5V,
and 1.8V), and jumper JP4 into the desired mode
of operation: Pulse Skip or Burst Mode.
Apply 3.3V at Vin. Measure both Vouts; they
should read 0V. If desired, one can measure the
shutdown supply current at this point. The supply
current will be approximately 33uA in shutdown,
with roughly 32uA due to the optional 100kΩ pullup resistor of the Power-On Reset (POR) feature.
This resistor can be removed, and the actual shutdown supply current (of approx. 1uA) can be
measured, if the POR feature is not required.
4.
Turn on Vout1 and Vout2 by changing jumpers JP1
and JP2 from the OFF position(s) to the ON position(s). Vary the input voltage from 2.5V to 5.5V
and adjust each load current from 0 to 800mA.
Both output voltages should be regulating.
5.
Set the load current of both outputs between
200mA and 800mA, and measure both output ripple voltages; they should measure less than 20
mVAC each. Also, observe the voltage waveform
at the switch node (pin 3) of each regulator. The
switching frequencies should be between 1.8MHz
and 2.7MHz (T = 0.555 us and 0.37 us), and each
switch node waveform should be rectangular in
shape.
6.
To change the mode of operation, change jumpers
JP1 and JP2 from the ON position(s) to the OFF
position(s). Then change jumper JP4 to the alternative position. Re-insert jumpers JP1 and JP2
into the ON position(s). Observe the voltage waveform at both switch nodes.
When finished, insert jumpers JP1 and JP2
OFF position(s) and disconnect the power.
to the
If more efficiency is desired from the Demo Circuit, replace the stock inductor, a Taiyo Yuden part #
LQLBC2518M2R2M, with a Murata inductor, # LQH32CN2R2M11. Due to its large size, the Murata inductor has
lower DCR than the Taiyo Yuden inductor, thus has less power dissipation.
2
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 734
DUAL SYNCHRONOUS, 800MA, 2.25 MHZ STEP-DOWN DC/DC REGULATOR
Figure 1. Proper Measurement Equipment Setup
Figure 2. Scope Probe Placement for Measuring Input or Output Ripple
3
5
4
3
2
1
* Capacitor C5 is an optional part. It was inserted on the DC734 to dampen the (possible) ringing voltage
due to the use of long input leads. On a normal, typical PCB, with short traces, the capacitor is not
needed.
Vin
Vin
2.5V-5.5V
JP1
CH.1
On
2
Off
Gnd
On
2
R1
4.7M
5%
U1
LTC3407-2EDD
R2
100K
R3
4.7M
5%
Off
VIN
1
E5
JP2
CH.2
1
Cin
10uF
6.3V
3
D
C5*
+ 47uF
10V
(Opt.)
3
E1
3
D
Vout1
1.2V/1.5V/1.8V
@ 800mA
R4
604K
RUN2
9
R5
604K
R8
402K
SW2
1
FBK1
11
GND
R9
301K
5
2
4
6
+
+
+
Vin
1
3
5
7
C2
22pF
FBK2
C
Vout2
2.5V @ 800mA
R6
887K
Cout2
10uF
6.3V
C4
(Opt.)
10
E3
Gnd
R7
280K
E6
R10
4.7M
5%
B
2
JP3
Vout1
E7
L2
2.2uH
C1
22pF
+
+
+
B
POR
MODE/SYNC
Cout1
10uF
6.3V
1.2V
1.5V
1.8V
E4
SW1
L1
2.2uH
C3
(Opt.)
Gnd
4
POR
8
6
E2
RUN1
GND
C
2
3
JP4
1
Burst Pulse
Mode Skip
LTC CONFIDENTIAL - FOR CUSTOMER USE ONLY
Customer Notice
A
5
4
LINEAR TECHNOLOGY CORPORATION
1630 McCARTHY BLVD.
MILPITAS, CA. 95035
408-432-1900
408-434-0507 FAX
Linear Technology Has Made A Best Effort To Design A
Circuit That Meets Customer-Supplied Specifications;
However, It Remains The Customer's Responsibility To
Verify Proper And Reliable Operation In The Actual
Application. Component Substitution And Printed
Circuit Board Layout May Significantly Affect Circuit
Performance Or Reliability. Contact Linear Technology
Applications Engineering For Assistance.
Size
Document Number
This Circuit Is Proprietary To Linear Technology And
Supplied For Use With Linear Technology Parts.
Date:
Wednesday, June 23, 2004
3
Title
A
Dual Synchronous Step-Down DC/DC Converter
Rev
Demo Circuit 734A LTC3407-2EDD
2
Sheet
1
1
of
1
Item
Qty
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
3
2
0
1
7
3
1
4
2
3
1
2
1
1
1
1
1
Reference
COUT1,COUT2,CIN
C2,C1
C3,C4 (Optional)
C5
E1,E2,E3,E4,E5,E6,E7
JP1,JP2,JP4
JP3
JP1,JP2,JP3,JP4
L1,L2
R1,R3,R10
R2
R4,R5
R6
R7
R8
R9
U1
Description
CAP, X5R 10uF 6.3V 20% 0805
CAP, NPO 22pF 50V 10% 0402
CAP, 0805
CAP, TANT 47uF 10V 20% 6032
TURRETS
HEADER, 3PIN 2mm
HEADER, 3X2 2mm
SHUNT,
INDUCTOR, 2.2uH
RES, 4.7M OHMS 5% 1/16W 0402
RES, 100K OHMS 1% 1/16W 0402
RES, 604K OHMS 1% 1/16W 0402
RES, 887K OHMS 1% 1/16W 0402
RES, 280K OHMS 1% 1/16W 0402
RES, 402K OHMS 1% 1/16W 0402
RES, 301K OHMS 1% 1/16W 0402
IC, LTC3407-2EDD
Part Number
TAIYO YUDEN JMK212BJ106MG
AVX 04025A220KAT
TBD
AVX TAJW476M010R
MILL-MAX 2501-2
COMM CON 2802S-03-G1
COMM CON 2202S-06G1
COMM CON, CCIJ2MM-138G
SUMIDA, CDRH2D18/LD2R2NC
AAC CR05-475JM
AAC CR05-1003FM
AAC CR05-6043FM
AAC CR05-8873FM
AAC CR05-2803FM
AAC CR05-4023FM
AAC CR05-3013FM
LINEAR TECH. LTC3407-2EDD
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