DC378A - Demo Manual

DC378 INTRODUCTION
Description
Demonstration circuit DC378 is a synchronous step-down buck regulator using the
LTC1778 No RSENSE switching regulator controller. The controller uses a valley
current control architecture to deliver very low duty cycles without requiring a sense
resistor. It provides high efficiency operation at light loads by means of discontinuous
mode operation. Noise and RF interference are reduced by a forced continuous control
pin. With a wide operating range of VIN = 4V to 36V and duty cycles of 2% to 90% at
200kHz, the LTC1778 is ideal for the applications such as notebook and palmtop
computers, PDAs, battery chargers and distributed power systems.
+
–
+
–
+
–
JP2
SD
RUN/SS
PGND
ON
VIN
5V–25V
GND
+
VOUT
2.5V/10A
JP1
DISC
CONT
–
+
–
LOAD
GND
LTC1778CGN
GND
No Rsense™ Wide Operating Range
DC/DC/Converter
EXTVCC
Figure 1. DC378A Test and Measurement Setup
Quick Start Guide
This demonstration board is easily set up to evaluate the performance of the LTC1778.
Please consult Figure 1 and follow the procedure outlined below for proper operation.
1.
Connect input power to the VIN and GND terminals. Input voltage is limited to
between 5V to 28V.
2.
Connect the load between the VOUT and GND terminals.
3.
Set the FCB Jumper JP1 to the lower position (CONT) to force continuous
synchronous operation at low loads, or to the upper position (DISC) to enable
discontinuous mode operation at low loads.
4.
To shut down the circuit, connect the RUN/SS pin to ground by setting jumper
JP2 to the SD position. Set JP2 to the ON position to enable normal operation.
5.
When measuring input or output ripple, see Figure 2 for proper scope probe
technique.
GND
Vout
Figure 2. Scope Probe Placement for Measuring Output Ripple
5
4
3
2
1
D
D
5 6 7 8
4
1
C
2
3
BOOST
16
PGOOD
TG
15
VRNG
SW
14
PGND
13
BG
12
RUN/SS
4
FCB
5
ITH
6
SGND
INTVcc
11
7
ION
VIN
10
8
VFB
EXTVcc
1 2 3
C
5 6 7 8
4
1 2 3
9
B
B
A
A
5
4
3
2
1
Bill Of Material
Demo Bd. #378A
Linear Technology Corporation
LTC1778CGN
6/16/2005
3:52 PM
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
32
33
34
35
36
1
1
1
1
3
0
2
1
1
0
1
1
1
1
1
8
2
1
1
1
1
1
1
1
1
1
1
1
1
1
2
4
4
1
2
1
CB1
CC1
CC2
CF
CIN1,CIN2,CIN3
CON (Optional)
COUT1,COUT2
CSS
CVCC
C1,C2,C3 (Optional)
C4
C5
C6
DB
D1
E1-E8
JP1,JP2
L2
M1
M2
RF1
RON
RPG1
RSS1
R1
R2
R3
R4
R5
U1
XJP2,XJP1
Part Description
Capacitor, X7R 0.22uF 16V 10%
Capacitor, X7R 560pF 25V 10%
Capacitor, NPO 100pF 50V 10%
Capacitor, Y5V 0.1uF 25V 80%
Capacitor, X5R 10uF 25V 20%
Capacitor, X7R 0.01uF 25V 10%
Capacitor, Spcl. Poly. 180uF 4V 20%
Capacitor, X7R 0.1uF 16V 10%
Capacitor, X5R 4.7uF 6.3V 20%
Capacitor, X7R TBD 50V 10%
Capacitor, X7R 0.01uF 25V 10%
Capacitor, X5R 22uF 6.3V 20%
Capacitor, Alum 10uF 35V 10%
Schottky Diode, Super-Mini
Schottky Rect., 40V/3Amp
Turret
Headers, 3 Pins 2mm Ctrs.
Inductor, 1uH, D104C
Mosfet., N-Chan. Red. Qg
Mosfet., N-Chan. Red. Qg
Resistor, Chip 1 OHM 0.06W 5%
Resistor, Chip 715K 0.06W 1%
Resistor, Chip 100K 0.06W 5%
Resistor, Chip 510K 0.06W 5%
Resistor, Chip 14K 0.06W 1%
Resistor, Chip 30.1K 0.06W 1%
Resistor, Chip 11K 0.06W 5%
Resistor, Chip 39K 0.06W 5%
Resistor, Chip 20K 0.06W 5%
I.C., NO Rsense Stepdown Controller
SHUNT, CCIJ2MM-138-G
STAND-OFF, NYLON HEX #4-40 1/4"
SCREW, #4-40, 1/4"
PRINTED CIRCUIT BOARDS
STENCIL
SOLDER FRAME
Page 1 - of - 1
Manufacture / Part #
AVX 0805YC224KAT1A
AVX 06033C561MAT2A
AVX 06035A101KAT1A
AVX 06033G104ZAT2T
Taiyo Yuden TMK432BJ106MM
AVX 06033C103KAT2A
PANASONIC EEFUE0G181R
AVX 0603YC104KAT1A
Taiyo Yuden JMK212BJ475MD-T
AVX 06035C101KAT1A
AVX 06033C103KAT2A
Taiyo Yuden JMK325BJ226MM-T
SANYO 35CV10gX
Central Semi. Corp CMDSH-3
B340A Diodes Inc.
Mill Max 2501-2
CommConn Con Inc. 2802S-03G2
Toko 919AS-1R0N
Siliconix Si4884DY
Siliconix Si4874DY
AAC CR16-1R0JM
AAC CR16-7153FM
AAC CR16-104JM
AAC CR16-514JM
AAC CR16-1402FM
AAC CR16-3012FM
AAC CR16-113JM
AAC CR16-393JM
AAC CR16-203JM
Linear Technology Corp. LTC1778CGN
COMM CON. CCIJ2MM-138-G
MICRO PLASTICS 14HTSP101
ANY
DEMO BOARD DC378A
STENCIL DC378A
FRAME S/N# 10695