Datasheet SC1534CM.TR, SC1534CS.TR Datasheet (Semtech Corporation)

400mA SmartLDO

TM

SC1534

PRELIMINARY - July 26, 2000

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DESCRIPTION

The SC1534 is designed to maintain a glitch-free 3.3V
output when at least one of two inputs, 5V (VIN) and

3.3V (VAUX), is present.
Whenever VIN exceeds a predetermined threshold

value, the internal 3.3V linear regulator is enabled, and
DR is pulled high.

When VIN falls below a lower threshold value, DR is
pulled low and the internal linear regulator is turned off.
DR has been designed to drive the gate of an external
low threshold P-channel MOSFET, which can be used
to connect the 3.3V supply directly to the regulator out­put. This ensures an uninterrupted 3.3V output even if
VIN falls out of specification. A maximum R

DS(ON)

of

200mΩ is recommended.
When both supplies are simultaneously available, the

drive pin (DR) will be pulled High, turning off the exter­nal PMOS switch.

The internal 5V detector has its upper threshold (for
VIN rising) set to 4.22V (typical) while the lower thresh­old (for VIN falling) is at 4.05V (typical) giving a hys­teresis of approximately 170mV.

The SC1534 is available in the popular SO-8 and 5­lead TO-263 surface mount packages.

BLOCK DIAGRAM

FEATURES

•= Glitch-free transition between input sources

•= Internal logic selects input source

•= Gate drive for external PMOS bypass switch

•= 5V detector with hysteresis

•= 1% regulated output voltage accuracy

•= 400mA load current capability

•= SO-8 and TO-263 packages

APPLICATIONS

•= Desktop Computers

•= Network Interface Cards (NICs)

•= PCMCIA/PCI Interface Cards

•= Cardbus

TM

Technology

•= Power supplies with multiple input sources

ORDERING INFORMATION

Part Number

SC1534CM.TR TO-263-5L
SC1534CS.TR SO-8
Note:

(1) Only available in tape and reel packaging.

(1)

Package

ABSOLUTE MAXIMUM RATINGS

Parameter Symbol Maximum Units

Input Supply Voltage VIN -0.5 to +7 V
Auxiliary Supply Voltage VAUX -0.5 to +7 V
LDO Output Current I
Operating Ambient

Temperature Range

O

T

10 to 400 mA

A

-5 to +70 °C

Operating Junction

T

-5 to +125 °C

J

Temperature Range
Storage Temperature

T

-65 to +150 °C

STG

Range
Lead Temperature

T

LEAD

300 °C

(Soldering) 10 Sec
Thermal Impedance

PIN CONFIGURATION

Top View

Junction to Ambient

(1)

SO-8
TO-263

θ

JA

65

°C/W

60

Thermal Impedance

SO-8

TO-263-5L

Junction to Case
SO-8
TO-263

ESD Rating ESD 2 kV

Note:
(1) 1 inch square of 1/16” FR-4, double sided, 1 oz. mini­mum copper weight.

θ

J C

39

°C/W

3

1

© 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320

400mA SmartLDO

TM

PRELIMINARY - July 26, 2000

PIN DESCRIPTION

Pin Name SO-8 Pin # TO-263-5L Pin # Pin Function

DR 4 5 Driver output for external P-channel MOSFET pass element.

GND 5,6,7,8 3/TAB Logic and power ground.

VAUX 1 1 This is the auxiliary input supply, nominally 3.3V.

VIN 2 2 This is the main input supply for the IC, nominally 5V.

VO 3 4 LDO 3.3V output.

APPLICATION CIRCUIT

Q1

SC1534

3.3VAUX
5V

5V

3.3VAUX

C1

0.1uF

C1

0.1uF

C2

4.7uF

C2

4.7uF

C3

0.1uF

C3

0.1uF

C5

0.1uF

3.3V OUT

C5

0.1uF

3.3V OUT

U1 SC1534CS

1

VAUX

2
3
4 5

U1 SC1534CM

2

VIN

1

VAUX

GND

VIN

GND

VO

GND

DR GND

TAB

DR

VO

GND

3

8
7
6

C4
10uF

Q1

5

4

C4
10uF

NOTE:

(1) External switch (Q1): use a low threshold P-channel MOSFET such as Fairchild FDN338P or International
Rectifier IRF7604, or equivalent. (PMOS, typical gate threshold voltage ~

1V, R

< 200mΩ at V

DS(ON)

= 2.7V).

GS

2

© 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320

400mA SmartLDO

TM

SC1534

PRELIMINARY - July 26, 2000

ELECTRICAL CHARACTERISTICS

Unless specified, TA = 25°C, VIN = 5V, VAUX = 3.3V, IO = 400mA, CO = 10µF. Values in bold apply over full operating temperature range.

Parameter Symbol Test Conditions MIN TYP MAX Units
VIN

Supply Voltage VIN VAUX = 0V
Quiescent Current I

Q

VIN = 5V, VAUX = 0V, IO = 0mA 8.0 11.0 mA

VIN = 5V, VAUX = 3.3V, I

Reverse Leakage From VAUX I

VIN

VAUX = 3.6V, VIN = 0V, IO = 0mA -1.5 -3.0 mA

VAUX

Supply Voltage VAUX
Quiescent Current I

Q(AUX)

VAUX = 3.3V, VIN = 0V, IO = 0mA 8.0 11.0 mA

VAUX = 3.3V, VIN = 5V, I

Reverse Leakage From VIN I

5V Detect

(1)(2)(3)

Low Threshold Voltage V

VAUX

TH(LO)

VIN = 5.5V, VAUX = 0V, IO = 0mA -5.0 -50.0 µA

VIN Falling, IO = 20mA 3.92 4.05 4.18 V

4.35 5.00 5.50

13.0

= 0mA 10.0 14.0 mA

O

15.0

-4.0

3.0 3.3 3.6

13.0

= 0mA 1.5 2.5 mA

O

3.0

-100.0

3.90 4.20

V

V

Hysteresis V

HYST

90 170 mV

80

High Threshold Voltage V

TH(HI)

VIN Rising, IO = 20mA

4.35

V

VO

LDO Output Voltage VO I

4.35V ≤ VIN ≤ 5.5V, 0mA ≤ I
Output Current I
Line Regulation REG

O

(LINE)

= 20mA 3.267 3.300 3.333 V

O

≤ 400mA

O

3.234 3.366
400

mA

VIN = 4.35V to 5.5V 0.20 0.60 %

0.80

Load Regulation REG

(LOAD)

IO = 20mA to 400mA 0.20 0.80 %

1.00

3

© 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320

400mA SmartLDO

TM

SC1534

PRELIMINARY - July 26, 2000

ELECTRICAL CHARACTERISTICS

Unless specified, TA = 25°C, VIN = 5V, VAUX = 3.3V, IO = 400mA, CO = 10µF. Values in bold apply over full operating temperature range.

Parameter Symbol Test Conditions MIN TYP MAX Units
Drive Output

Drive Voltage V

Peak Drive Current I

Drive High Delay

Drive Low Delay

(1)(4)

(1)(4)

DR

DR(PK)

t

DH

t

DL

4.35V ≤ VIN ≤ 5.5V, IDR = 200µA

VIN < V

, IDR = -200µA 35 150 mV

TH(LO)

Sinking: VIN = 3.9V, VDR = 1V; 7 mA

Sourcing: VIN = 4.35V, VIN - V

= 2.5V

DR

CDR = 1.2nF, VIN ramping up, measured 0.5 1.0 µs

from VIN = V

to VDR = 2V

TH(HI)

CDR = 1.2nF, VIN ramping down, measured 0.5 1.0 µs

from VIN = V

to VDR = 2V

TH(LO)

NOTES:

(1) Guaranteed by design.
(2) See 5V Detect Thresholds on page 5.
(3) Recommended source impedance for 5V supply: ≤ 0.125Ω. This will ensure that I
avoiding DR toggling during 5V detect threshold transitions.
(4) See Timing Diagram on page 5.

3.4 VIN - 0.8 V

3.3

250

6

2.0

2.0

x R

O

SOURCE

< V

HYST

, thus

4

© 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320

PRELIMINARY - July 26, 2000

5V DETECT THRESHOLDS

400mA SmartLDO

TM

SC1534

NOTE:

(1) VIN rise and fall times (10% to 90%) to be ≥=100µs.

TIMING DIAGRAM

NOTE:

(1) VIN rise and fall times (10% to 90%) to be ≤=100ns.

5

© 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320

PRELIMINARY - July 26, 2000

OUTLINE DRAWING - SO-8

400mA SmartLDO

TM

SC1534

JEDEC

REF: MS-012AA

MINIMUM LAND PATTERN - SO-8

6

© 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320

PRELIMINARY - July 26, 2000

DEVICE OUTLINE - TO-263, 5 PIN

400mA SmartLDO

TM

SC1534

MINIMUM LAND PATTERN - TO-263, 5 PIN

ECN00-1212

7

© 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320