Datasheet SC1537CM.TR, SC1537CS.TR Datasheet (Semtech Corporation)

700mA SmartLDO

TM

SC1537

PRELIMINARY - July 25, 2000

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DESCRIPTION

The SC1537 is designed to m aintain 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 tur ned of f .
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 s pecification. A maximum R
100mΩ is recommended.

When both supplies are simultaneously available, the
drive pin (DR) will be pulled High, turning off the exter ­nal 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 SC1537 is available in the popular SO-8 and
5-lead TO-263 surface mount packages.

DS(ON)

Q1

of

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

•= 700mA 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

SC1537CSTR SO-8
SC1537CMTR TO-263-5L

Note:
(1) Only available in tape and reel packaging. A reel con­tains 2500 devices for SO-8 and 800 devices for TO-263.

(1)

Package

APPLICATION CIRCUIT

C5

0.1uF

C5

0.1uF

3.3V OUT

3.3V
5V

C3

C2

C1

0.1uF

5V

3.3V 3.3V OUT

C1

0.1uF

10uF

C2
10uF

0.1uF

C3

0.1uF

U1 SC1537CS

1

VAUX

GND

2

VIN

GND

3

VO

GND

4 5

DR GND

U1 SC1537CM

2

TAB

VIN

1

VAUX

GND

3

8
7
6

C4
10uF

Q1

5

DR

4

VO

C4
10uF

NOTE:

(1) External switch (Q1): use a low threshold P-channel MOSFET such as Vishay Si2305DS (R

= 2.5V) or International Rectifier IRLML6401 (R

V

GS

< 85mΩ at VGS = 2.5V), or equivalent.

DS(ON)

DS(ON)

< 71mΩ at

1

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

700mA SmartLDO

TM

SC1537

PRELIMINARY - July 25, 2000

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 T
Operating Junction Temperature Range T
Storage Temperature Range T
Lead Temperature (Soldering) 10 Sec T
Thermal Impedance Junction to Ambient

(1)

SO-8
TO-263

O

STG

LEAD

θ

JA

A

J

10 to 700 mA

0 to +70 °C

0 to +125 °C

-65 to +150 °C
300 °C

65

°C/W

60

Thermal Impedance
Junction to Case
SO-8
TO-263

θ

J C

39

3

°C/W

ESD Rating (Human Body Model) ESD 2 kV
Note:

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

ELECTRICAL CHARACTERISTICS

Unless specified, TA = 25°C, VIN = 5V, VAUX = 3.3V, IO = 700mA, 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 9.0 14.0 mA

4.75 5.00 5.25

V

16.0

VIN = 5V, VAUX = 3.3V, I

= 0mA 13.0 17.0 mA

O

18.0

Reverse Leakage From VAUX I

VIN

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

-4.0

VAUX

Supply Voltage VAUX
Quiescent Current I

Q(AUX)

3.0 3.3 3.6

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

V

13.0

VAUX = 3.3V, VIN = 5V, I

= 0mA 1.5 2.5 mA

O

3.0

2

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

700mA SmartLDO

TM

SC1537

PRELIMINARY - July 25, 2000

ELECTRICAL CHARACTERISTICS

Unless specified, TA = 25°C, VIN = 5V, VAUX = 3.3V, IO = 700mA, CO = 10µF. Values in bold apply over full operating temperature range.

Parameter Symbol Test Conditions MIN TYP MAX Unit
VAUX (Cont.)

Reverse Leakage From VIN I

5V Detect

(1)(2)(3)

Low Threshold Voltage V

Hysteresis V

High Threshold Voltage V

VAUX

TH(LO)

HYST

TH(HI)

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

VIN Falling, IO = 20mA 3.92 4.05 4.18 V

VIN Rising, IO = 20mA

VO

LDO Output Voltage VO I

4.75V ≤ VIN ≤ 5.25V, 0mA ≤ I
Output Current I
Line Regulation REG

Load Regulation REG

O

(LINE)

(LOAD)

VIN = 4.75V to 5.25V 0.20 0.60 %

IO = 10mA to 700mA 0.6 1.0 %

-

100.0

3.90 4.20

90 170 mV

80

4.35

= 20mA 3.267 3.300 3.333 V

O

≤ 700mA

O

3.234 3.366
400

0.80

1.2

V

mA

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

4.75V ≤ VIN ≤ 5.25V, 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

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: ≤ 0.07Ω. 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

0.5 1.0 µs

2.0

x R

O

SOURCE

< V

HYST

, thus

3

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

PRELIMINARY - July 25, 2000

BLOCK DIAGRAM

700mA SmartLDO

TM

SC1537

PIN CONFIGURATION

Top View

TO-263-5LSO-8

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.

4

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

PRELIMINARY - July 25, 2000

5V DETECT THRESHOLDS

700mA SmartLDO

TM

SC1537

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 25, 2000

OUTLINE DRAWING - SO-8

700mA SmartLDO

TM

SC1537

JEDEC

REF: MS-012AA

MINIMUM LAND PATTERN - SO-8

6

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

PRELIMINARY - July 25, 2000

DEVICE OUTLINE - TO-263, 5 PIN

700mA SmartLDO

TM

SC1537

MINIMUM LAND PATTERN - TO-263, 5 PIN

ECN00-1177

7

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