DC326B - Demo Manual

DEMO MANUAL DC326B
NO-DESIGN SWITCHER
OPERATION
How to Measure Voltage Regulation and Efficiency
When measuring voltage regulation or efficiency, voltage measurements should be made directly across the VOUT and GND terminals, not at
the end of test leads at the load. Similarly, input voltage should be measured directly at the VIN and GND terminals of the LT1766 demo board.
Input and output current should be measured by placing an ammeter in series with the input supply and load. Refer to figure 2 for proper
monitoring equipment setup.
How to Measure Output Voltage Ripple
When measuring output voltage ripple, care must be taken to avoid a long ground lead on the oscilloscope probe. A sturdy wire should be
soldered to the output side of the GND terminal. The other end of the wire is looped around the ground side of the probe and should be kept
as short as possible. The tip of the probe is touched directly to VOUT (see Figure 3). Bandwidth is generally limited to 20MHz for ripple
measurements. Also, if multiple pieces of line-powered test equipment are used, be sure to use isolation transformers on their power lines
to prevent ground loops, which can cause erroneous results. Figure 4 shows the output voltage ripple with a steady-state load of 1A for the
LT1766.
Heat Dissipation Issues
Since the LT1766 includes a 1.5A onboard power switch, care must be taken not to exceed the 125c maximum operating junction temperature
for the part. A simple technique is to use the PC board as a heat sink. On the LT1766 demo board, the power IC is surrounded by ground plane
on both sides of the PC board. The two sides are connected through vias to better handle the power dissipation. If the LT1766 is laid out on a
multilayer board, there should be metal on the inner layers directly underneath the LT1766. This helps in spreading heat and improves the
power dissipation capability of the PCB. Note: See 'Thermal Calculations' section in the Applications Information of the LT1766 datasheet.
DEMO MANUAL DC326B
NO-DESIGN SWITCHER
OPERATION
Efficiency vs. Load Current
100
Vout = 5V
L = 47uH
Vin=12V
90
Efficiency (%)
Introduction
The LT1766 is a 1.5A 200kHz Step-Down switching regulator capable of
operation at input voltages as high as 60V. The demonstration circuit shown
in the schematic allows for output selection of 3.3V or 5V using the jumper J1.
The board comes equipped with input (VIN), output (VOUT), GND, SYNC and
S/D terminals to simplify bench testing. The demonstration circuit highlights the
ability of the LT1766 to achieve excellent efficiencies at both high and low
input voltages. The efficiency curves in Figure 1 illustrate both 42V to 5V and
12V to 5V conversions with peak efficiencies of greater than 80% and 90%.
80
Vin=42V
70
60
50
0.00
0.25
0.50
0.75
1.00
1.25
Load Current (A)
Figure 1. LT1766 efficiency vs. Load Current
Shutdown Pin
For normal operation, the S/D pin can be left floating. S/D has two output-disable modes, lockout and shutdown.
When the pin is taken below the 2.38V lockout threshold, switching is disabled. This is typically used for input undervoltage lockout.
Grounding the S/D pin places the LT1766 in shutdown mode. This reduces total board supply current to typically 25uA.
Synchronization Pin
To synchronize switching to an external clock, apply a logic-level signal to the SYNC pin. Amplitude must be from a logic
low level to greater than 2.2V with a duty cycle from 10% to 90%. Synchronization frequency is possible from 228kHz
up to 700kHz.
Quick Start Guide
A list of procedures for getting started, including the basic set-up for measurement equipment, are provided in the 'quick start guide'
attached.
NOTE: The LT1766 datasheet should be read in conjunction with the demonstration board information provided.
DEMO MANUAL DC326B
NO-DESIGN SWITCHER
QUICK START GUIDE
Refer to Figure 2 for proper measurement
setup and follow the procedure outlined below :
1. Connect the input power supply to the VIN and GND
terminals. The input voltage must be between 5.5V and 60V.
6. Set the output voltage with the jumper J1,
as shown in the table below.
2. Connect an ammeter in series with the input supply to
measure input current.
7. After all connections are made, turn on input
power and verify that the output voltage is correct.
3. Connect either power resistors or an electronic load
to the VOUT and GND terminals.
4. Connect an ammeter in series with the output load to
measure output current.
5. The S/D pin should be left floating for normal operation
and tied to GND for shutdown.
POSITION
Jumper J1 open
Jumper J1 inserted
OUTPUT VOLTAGE
5.0V
3.3V
1
2
REVISION HISTORY
LTC CONFIDENTIAL - For Customer Use Only
ECO
REV
1
DESCRIPTION
DATE
DEMO BOARD RELEASE
APPROVED
11/29/00
D2
FMMD914
1
D3
Opt.
C4
0.33uF
E1
3
VIN
L1
E5
VOUT
1
+ C3
4.7uF
100V
6
Opt.
E2
GND
4
VIN
E3
S/D
+ C5
100uF
10V
U1
LT1766CGN
+ C7
Opt.
R2
15.4K
1%
R4
19.1K
1%
C6
0.47uF
25V
D1
SW
E4
JP1
2
GND
10MQ060N
15
SHDN
BIAS
10
14
SYNC
FB
12
5V/3.3V
LINK
VC
E6
C9
Opt.
11
SYNC
A
68uH
BOOST
A
3
C1
1000pF
R6
Opt.
3
R1
Opt.
Q1
Opt.
1
R5
Opt.
2
C2
Opt.
R3
4.99K
1%
NOTE: UNLESS OTHERWISE SPECIFIED
1. FUSED CORNER PINS 1, 8, 9 ,16 (GND) - U1.
B
B
UNLESS OTHERWISE SPECIFIED
DIMENSIONS ARE IN INCHES
TOLERANCE ON ANGLE - - 2 PLACES - - - 3 PLACES - - INTERPRET DIM AND TOL
PER ASME Y14.5M -1994
THIRD ANGLE PROJECTION
CONTRACT NO.
APPROVALS
DATE
DRAWN L.SANTOS
7/14/00
TECHNOLOGY
1630 McCarthy Blvd.
Milpitas, CA 95035
Phone: (408)432-1900
Fax: (408)434-0507
TITLE
CHECKED
SCH, 1.5A 200KHz HIGH VOLTAGE BUCK CONVERTER PCB
APPROVED
ENGINEER
DESIGNER
SIZE CAGE CODE
DWG NO
A
DO NOT SCALE DRAWING
1
Wednesday, November 29, 2000
SCALE: NONE
REV
DC326B
FILENAME:326Br1.DSN
2
SHEET
1
1
OF
1
Linear Technology Corporation
LT1766CGN (SSOP16)
Item Qty Reference
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
1
1
0
1
1
1
1
0
0
0
0
1
0
1
0
6
1
1
0
1
0
0
1
1
1
0
0
1
1
4
4
C1
C3
C3 (Option2)
C4
C5
C6
C2
C7 (Option 1)
C7 (Option 2)
C9 (Option)
C12 (Option)
D1
D1 (Option)
D2
D3 (Option)
E1-E6
J1
J1
L1 (Option 3)
L1
L1 (Option 2)
Q1 (Option)
R2
R3
R4
R5 (Option)
R6 (Option)
R1
U1
MH1-MH4
MH1-MH4
Printed: 6/16/2005
Rev. 2
Bills Of Material
Demo DC326B
Part Description
Capacitor, X7R 220pF 50V 10%
Capacitor, chip 4.7uF 100V
Capacitor, chip 150uF 63V AL ELECT
Capacitor, X7R 0.33uF 16V 10%
Capacitor, Tant. 100uF 10V 20%
Capacitor, Y5V 0.47uF 25V 80%
Capacitor, X7R .022uF 16V 10%
Capacitor, Tant. 100uF 10V 20%
Capacitor, X5R, 47uF, 6.3V
CAP, .1UF, 25V Y5V, 0603
Capacitor, X7R, 1000pF, 50V, 10%
Diode Schottky,1.5A, 60V
Diode Schottky,3A, 60V
Diode, 200mA, 100V
Diode, 200mA, 100V
Test Point,
Header, 2pin, 1 Row, .079CC
Shunt, .079" center
Inductor, 68uH
Inductor, 33uH
Inductor, 47uH
Xstr, NPN, SOT23
Resistor, Chip 15.4K 1%
Resistor, Chip 4.99K 1%
Resistor, Chip 19.1K 1%
Resistor, Chip XXK 1%
Resistor, Chip 2K 1%
Resistor, Chip, 2.2K, 5%, 1/8W
I.C. LT1766
STAND-OFF, NYLON HEX #4-40x1/4"
SCREW, #4-40 x 1/4
Page 1 - of - 1
Manufacture / Part #
AVX 08055A221KAT
MARCON THCR70E2A475ZT
PANASONIC ECA63FQ150L
AVX 0805YC334KAT1A
AVX TPSD107M010R0100
AVX 08053G474ZAT1A
AVX 0805YC223KAT
AVX TPSD107M010R0100
TAIYO YUDEN JMK432BJ476MM
AVX 06033G104ZAT
AVX 08055C102KAT
IR 10MQ060N
OPT:MOTOROLA MBRS360T4
ZETEX FMMD914TA
MILL MAX 2501-2
COMM-CON 2802S-02-G1
COMM CON CCIJ2MM-138G
COOPER ELECTRONICS UP2-680
SUMIDA CDRH125-330MC
COOPER ELECTRONICS UP2-470
AAC CR10-1542FM
AAC CR10-4991FM
AAC CR10-1912FM
AAC
AAC
AAC CR10-222JM
LINEAR TECHNOLOGY LT1766EGN or LT1766IGN
MICRO PLASTICS #14HTSP101
ANY
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