Linear LTC1474, LTC1475, LTC1474-3.3, LTC1474-5, LTC1475-3.3 Demo Manual

DEMO MANUAL DC143

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DESCRIPTIO

This demonstration circuit is a step-down (buck) regulator
using the LTC®1474/LTC1475. The exclusive use of surface
mount components and the LTC1474/LTC1475 in the tiny
MSOP package results in a highly efficient application in a
small board space. This demo board highlights the
capabilities of the LTC1474/LTC1475, which use a current
mode, constant off-time architecture to switch an internal
P-channel power MOSFET. This results in a power supply
that has low ripple and fast transient response. At low
output currents the LTC1474/LTC1475 automatically
switch to Burst ModeTM operation to maintain high operating
efficiencies and minimize supply current. At no load,only

DEMO MANUAL DC143

NO DESIGN SWITCHER

LTC1474/LTC1475

10µA I

, High Efficiency,

Q

Step-Down DC/DC

Converter

10µA (typical) is required to regulate the output. The parts
can be shut down to further reduce the supply current to
6µA (typical). In dropout, the internal P-channel MOSFET
is turned on continuously (100% duty cycle), providing
low dropout operation with V
battery detector allows the user to monitor the input
supply through an external resistive divider. This board is
intended for applications such as cellular phones, GSM
systems, 4mA to 20mA current-loop pirate supplies or any
portable battery-powered application. Gerber files for this

circuit board are available. Call the LTC factory.

, LTC and LT are registered trademarks of Linear Technology Corporation.

Burst Mode is a trademark of Linear Technology Corporation.

≅ VIN. An onboard low-

OUT

UW

WW

PERFORmANCE SU ARY

SYMBOL PARAMETER CONDITIONS BOARD SUFFIX VALUE

V

V

I

I

IN

OUT

OUT

Q

Input Voltage Range V

Output Voltage LTC1474/LTC1475 A, D 3.3V ± 0.10V

Maximum Output Current R

Typical Supply Current VIN = 10V, I

U

W

= 3.3V A, B, D, E 3.3V to 18V

OUT

= 5V C, F 5V to 18V

V

OUT

LTC1474-3.3/LTC1475-3.3 B, E 3.3V ± 0.10V
LTC1474-5/LTC1475-5 C, F 5V ± 0.15V

= 0Ω ALL 300mA

SENSE

= 0.25Ω ALL 150mA

R

SENSE

= 0 A, B, C 10µA

LOAD

V

IN

= 10V, I

= 0 D, E, F 15µA

LOAD

U

TYPICAL PERFOR A CE CHARACTERISTICS A D BOARD PHOTO

Board A, B, D, E Efficiency Demo Board A

100

VIN = 5V

90

80

VIN = 10V

VIN = 15V

Demo Board D

70

EFFICIENCY (%)

60

50

0.03 3 30 300

0.3
LOAD CURRENT (mA)

L = 100µH

= 3.3V

V

OUT

R

= 0Ω

SENSE

DM143 TPC

DM143 DB A

DM143 DB D

1

DEMO MANUAL DC143

1
2
3
4

V

OUT

(VFB*)

LBO

LBI

GND

8
7
6
5

RUN
V

IN


SENSE
SW

TOP VIEW

MS8 PACKAGE

8-LEAD PLASTIC MSOP



*ADJUSTABLE OUTPUT VERSION

UW

WW

PERFORmANCE SU ARY

SYMBOL PARAMETER CONDITIONS BOARD SUFFIX VALUE

V

RIPPLE

∆V

V

LBI

OUT

Typical Output Ripple I
Typical Line Regulation 4V < VIN < 18V, R

Typical Load Regulation 0 < I

= 100mA All 50mV

OUT

< 18V, R

4V < V

IN

4V < VIN < 18V, R
4V < VIN < 18V, R

6V < VIN < 18V, R

< 18V, R

6V < V

IN

< 300mA, R

LOAD

0 < I

< 150mA, R

LOAD

SENSE
SENSE

SENSE
SENSE

SENSE
SENSE

= 0Ω, I
= 0.25Ω, I

= 0Ω, I
= 0.25Ω, I

= 0Ω, I
= 0.25Ω, I

SENSE
SENSE

= 100mA A, D 35mV

LOAD

= 100mA 25mV

LOAD

= 100mA B, E 20mV

LOAD

= 100mA 10mV

LOAD

= 100mA C, F 20mV

LOAD

= 100mA 10mV

LOAD

= 0Ω, VIN = 10V All 10mV
= 0.25Ω, VIN = 10V 10mV

Low-Battery Trip Threshold All 1.23V

W UW

PACKAGE A D SCHE ATIC DIAGRA SM

VIN

4V* TO 18V

LBI

*3.3V AT NO LOAD

4.7µF

35V

C3

+

C1



R6
0Ω

JP1

RUN

R1

0.25Ω

R7

100k

C2
1000pF

6

3

8

SENSE

LBI

RUN

7

V

IN

LTC1474

GND

4

V

LBO

SW

0.1µF

FB

C5

1

2

5

10pF

R5

R4

THIS NETWORK
IS PRESENT IN
BOARD A ONLY

+

L1 
100µH

D1
MBR0530

C4
100µF

6.3V

V

OUT

3.3V
300mA

LBO

DM143 F01

LTC1474CMS8
LTC1474CMS8-3.3
LTC1474CMS8-5

Figure 1. LTC1474 Demo Board Schematic

VIN

4V* TO 18V

4.7µF

LBI

*3.3V AT NO LOAD

35V

+

C1



3.01M

1M

R3

R2

R6
0Ω

SHDN

R1

0.25Ω

R7

100kRUN

C2
1000pF

Figure 2. LTC1475 Demo Board Schematic

2

6

3

8

SENSE

LBI/OFF

ON

7

V

IN

LTC1475

GND

4

V

LBO

SW

0.1µF

FB

C3

C5

1

2

5

10pF

R5

R4

THIS NETWORK
IS PRESENT IN
BOARD D ONLY

+

L1 
100µH

D1
MBR0530

C4
100µF

6.3V

V

OUT (VFB

LBO

LBI/OFF

GND

V

OUT

3.3V
300mA

*ADJUSTABLE OUTPUT VERSION

TOP VIEW

1

*)

2
3
4

MS8 PACKAGE

8-LEAD PLASTIC MSOP



LTC1475CMS8
LTC1475CMS8-3.3

8
7
6
5

ON
V



IN

SENSE
SW

LTC1475CMS8-5

LBO

DM143 F02

DEMO MANUAL DC143

PARTS LIST

REFERENCE
DESIGNATOR QUANTITY PART NUMBER DESCRIPTION VENDOR TELEPHONE

C1 1 TPSC475M035 4.7µF 35V 20% Tantalum Capacitor AVX [phone]
C2 1 080553102KAT2A 1000pF 25V 10% X7R Capacitor AVX [phone]
C3 1 08055310KAT1A 10pF 25V 10% NPO Capacitor (Boards B, C, E, F Only) AVX [phone]
C4 1 TPSC107M006R0150 100µF 6.3V 20% Tantalum Capacitor (Boards A, B, D, E) AVX [phone]

TPSC336M010R0375 33µF 6.3V 20% Tantalum Capacitor (Boards C, F)

C5 1 08053E104ZAT1A 0.1µF 25V +80% to –20% Y5V Capacitor AVX [phone]
D1 1 MBR0530 0.5A 30V Schottky Diode Motorola [phone]
E1 to E6 6 2501-02 Terminal Turret Mill Max [phone]
JP1 1 2802S-02-G2 Connector Pin Header (Boards A, B, C) Comm Con [phone]
L1 1 CDRH73-101 100µH Inductor Sumida [phone]
R1 1 LR1206 01 R250 F0 0.25Ω 0.25W 1% Resistor IRC [phone]
R2 1 CR21-105J-T 1M 0.1W 5% Resistor (Boards D, E, F Only) AVX [phone]
R3 1 CR21-225J-T 2.2M 0.1W 5% Resistor (Boards D, E, F Only) AVX [phone]
R4 1 WCR0805-1474-F-P-LT 1.47M 0.1W 1% Resistor (Boards B, C, E, F Only) IRC [phone]
R5 1 CJ21-000J-T 0805 Shunt Resistor (Boards B, C, E, F) AVX [phone]

WCR0805-2494-F-P-LT 2.49M 0.1W 1% Resistor (Boards A, D) IRC [phone]
R6 1 CJ21-000J-T 0805 Shunt Resistor AVX [phone]
R7 1 CR21-104J-T 100k 0.1W 5% Resistor AVX [phone]
S1, S2 2 EVQ PJS05K Momentary Switch (Boards D, E, F) Panasonic [phone]
U1 1 LTC1474CMS8 8-Pin MSOP IC, LTC1474 (Board A) LTC [phone]

LTC1474CMS8-3.3 8-Pin MSOP IC, LTC1474-3.3 (Board B)

LTC1474CMS8-5 8-Pin MSOP IC, LTC1474-5 (Board C)

LTC1475CMS8 8-Pin MSOP IC, LTC1475 (Board D)

LTC1475CMS8-3.3 8-Pin MSOP IC, LTC1475-3.3 (Board E)

LTC1475CMS8-5 8-Pin MSOP IC, LTC1475-5 (Board F)

Table 1. Demo Board Version Cross Reference

BOARD SUFFIX PART NUMBER OUTPUT VOLTAGE ON/OFF CONTROL

A LTC1474 3.3V (Adjustable) Jumper
B LTC1474-3.3 3.3V Jumper

C LTC1474-5 5V Jumper
D LTC1475 3.3V (Adjustable) Pushbutton
E LTC1475-3.3 3.3V Pushbutton

F LTC1475-5 5V Pushbutton

3