Linear Technology LTC1473L Datasheet

FEATURES

PowerPath

DESCRIPTIO

LTC1473L

Dual Low Voltage

TM

Switch Driver

U

■

Power Path Management for Systems
with Multiple DC Sources

■

Switches and Isolates Sources from 3.3V to 10V

■

All N-Channel Switching to Reduce Power Losses
and System Cost

■

Built-In Step-Up Regulator for N-Channel Gate Drive

■

Capacitor Inrush and Short-Circuit Current Limited

■

User-Programmable Timer Prevents Overdissipation
During Current Limiting

■

Undervoltage Lockout Prevents Operation with Low
Inputs

■

Small Footprint: 16-Pin Narrow SSOP

U

APPLICATIO S

■

Portable Computers

■

Portable Instruments

■

Fault Tolerant Computers

■

Battery-Backup Systems

■

3.3V/5V Power Management

The LTC®1473L provides reliable and efficient switching
between two DC power sources. This device drives two
external sets of back-to-back N-channel MOSFET switches
to route power to the input of a low voltage system. An
internal boost regulator provides the voltage to fully en­hance the logic-level N-channel MOSFET switches while
an internal undervoltage lock-out circuit keeps the system
alive down to 2.8V.

The LTC1473L senses current to limit inrush between the
batteries and the system supply capacitor during switch­over transitions or during fault conditions. A user-pro­grammable timer monitors the time the MOSFET switches
are in current limit and latches them off when the pro­grammed time is exceeded.

A unique “2-diode” logic mode ensures system start-up
regardless of which input receives power first.

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

PowerPath is a trademark of Linear Technology Corporation.

TYPICAL APPLICATIO

DCIN

3.3V

V

BAT1

4× NiMH

C

TIMER

2000pF

1µF

* COILCRAFT 1812LS-105XKBC

BAT54C

U

1µF

3.3V to 4-Cell NiMH Backup Switch

LOGIC

DRIVEN

1mH*

1
2
3
4
5
6
7
8

IN1
IN2
DIODE
TIMER

+

V
V

GG

SW
GND

LTC1473L

GA1

SAB1

GB1
SENSE
SENSE

GA2

SAB2

GB2

16
15
14
13

+

12

–

11
10
9

Si9926DY

Si9926DY

R

SENSE

0.04Ω

1473 TA01

3.3V OR
V

+

BAT1

C

OUT

1

LTC1473L

WW

W

ABSOLUTE AXI U RATI GS

(Note 1)

SENSE+, SENSE–, V+..................................–0.3 to 10V

GA1, GB1, GA2, GB2 ...................................–0.3 to 20V

SAB1, SAB2.................................................–0.3 to 10V

SW, VGG......................................................–0.3 to 20V

IN1, IN2, DIODE...........................................–0.3V to 7V

Junction Temperature (Note 2).............................125°C

Operating Temperature Range.....................0°C to 70°C

Storage Temperature Range................. –65°C to 150°C

Lead Temperature (Soldering, 10 sec)..................300°C

U

UUW

PACKAGE/ORDER I FOR A TIO

TOP VIEW

IN1

1

IN2

2

DIODE

3

TIMER

4

+

V

5

V

6

GG

SW

7

GND

8

GN PACKAGE

16-LEAD NARROW PLASTIC SSOP

T

= 125°C, θJA = 150°C/W

JMAX

16
15
14
13
12
11
10

9

GA1
SAB1
GB1
SENSE
SENSE
GA2
SAB2
GB2

+
–

ORDER PART

NUMBER

LTC1473LCGN

GN PART MARKING

1473L

Consult factory for Military and Industrial grade parts.

ELECTRICAL CHARACTERISTICS

The ● denotes the specifications which apply over the full operating

temperature range, otherwise specifications are at TA = 25°C. Test circuit, V+ = 5V, unless otherwise specified.

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

+

V
I

S

V

GS

+

V

UVLO

+

V

UVLOHYS

V

HIDIGIN

V

LODIGIN

I

IN

V

GS(ON)

V

GS(OFF)

I

BSENSE

I

BSENSE

V

SENSE

I

PDSAB

I

TIMER

V

TIMER

t

ON

t

OFF

t

D1

t

D2

f

OVGG

Supply Operating Range 2.8 9 V
Supply Current V

IN1

= V

DIODE

= 5V, V

IN2

= 0V, V

SENSE

+

= V

–

= 5V ● 100 200 µA

SENSE

VGS Gate Supply Voltage VGS = VGG – V+, 2.8V ≤ V+ ≤ 10V (Note 3) ● 7.5 8.5 9.5 V
V+ Undervoltage Lockout Threshold V+ Ramping Down ● 2.3 2.5 2.8 V
V+ Undervoltage Lockout Hysteresis 70 mV
Digital Input Logic High (Note 4) ● 2 0.9 V
Digital Input Logic Low (Note 4) ● 0.6 0.4 V
Input Current V
Gate-to-Source ON Voltage I
Gate-to-Source OFF Voltage I

+

SENSE+ Input Bias Current V

–

SENSE– Input Bias Current V

Inrush Current Limit Sense Voltage V

SAB1, SAB2 Pull-Down Current V

Timer Source Current V

Timer Latch Threshold Voltage V
Gate Drive Rise Time C
Gate Drive Fall Time C
Gate Drive Turn-On Delay C
Gate Drive Turn-Off Delay C

= V

IN1

= I

GA1

= I

GA1

SENSE

V

SENSE
SENSE

V

SENSE
SENSE–

V

SENSE–

= V

IN1

= V

V

IN1

= 0.4V, V

IN1

V

SENSE

= 0.4V, V

IN1

= 1000pF, V

GS

= 1000pF, V

GS

= 1000pF, V

GS

= 1000pF, V

GS

= V

IN2

= I

GA2

= I

GA2
+

= V

SENSE

+

= V

SENSE

+

= V

SENSE–

+

= V

SENSE

= 10V (V
= 0V (V

= V

IN2

= 0.4V, V

IN2

+

– V

SENSE

= 5V ±1 µA

DIODE

= I

GB1
GB1

DIODE

IN2

IN2

= –1µA, V

GB2

= I

= 100µA, V

GB2

–

= 10V (Note 3) ● 24.510µA

–

= 0V (Note 5) ● –300 –175 –75 µA
= 10V (Note 3) ● 24.510µA

–

= 0V (Note 5) ● –300 –175 –75 µA

– V

SENSE+

SENSE+

– V

SENSE

SENSE

= 0.4V, V+ = 10V (Note 3) 5 20 35 µA

= 2V 30 140 300 µA

DIODE

= V

= V

SAB1
SAB1
SAB1
SAB1

= 2V, V

DIODE

–

= 300mV

= 2V ● 1.05 1.16 1.25 V

DIODE

= V

= 0V (Note 6) 33 µs

SAB2

= V

= 5V (Note 6) 2 µs

SAB2

= V

= 0V (Note 6) 22 µs

SAB2

= V

= 5V (Note 6) 1 µs

SAB2

= V

SAB1

SAB1

–

) (Note 3) 0.15 0.20 0.25 V

–

) 0.10 0.20 0.30 V

TIMER

= 5V ● 4.5 5.6 7.0 V

SAB2

= V

= 5V ● 0 0.4 V

SAB2

= 0V, ● 369µA

VGS Regulator Operating Frequency 30 kHz

2

ELECTRICAL CHARACTERISTICS

LTC1473L

Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.

Note 2: T
dissipation P

is calculated from the ambient temperature TA and power

J

according to the following formula:

D

TJ = TA + (PD)(150°C/W)

Note 3: Some tests are performed under more stringent conditions to
ensure reliable operation over the entire supply voltage range.

Note 4: Digital inputs include: IN1, IN2 and DIODE.
Note 5: I

increases by the same amount as I

S

their common mode falls below 5V.
Note 6: Gate turn-on and turn-off times are measured with no inrush

current limiting, i.e., V

4.5V and fall times are measured from 4.5V to 1V. Delay times are
measured from the input transition to when the gate voltage has risen or
fallen to 3V. Results are not tested, but guaranteed by design.

UW

TYPICAL PERFOR A CE CHARACTERISTICS

DC Supply Current
vs Supply Voltage

250

200

150

100

SUPPLY CURRENT (µA)

50

0

0

V

SENSE

+

= V

2 45678913

+

–

= V

SENSE

V

= V

DIODE

IN1

V

IN2

V

DIODE

V

IN1

SUPPLY VOLTAGE (V)

= 5V
= 0V

= V

= 5V

IN2

= 0V

10

1473 G01

DC Supply Current
vs Temperature

140

V+ = 5V

130
120
110
100

90

80

SUPPLY CURRENT (µA)

70

60
50

–25 25 50 75 100

–50

V

= V

DIODE

TEMPERATURE (°C)

= 5V

IN1

V

= 0V

IN2

0

1473 G02

+

+ I

BSENSE

= 0V. Gate rise times are measured from 1V to

SENSE

DC Supply Current vs V

400
350
300
250
200
150

SUPPLY CURRENT (µA)

100

50

0

0

V

V+ = 5V
V

DIODE

V

IN2

V

SENSE

567 101234 89

COMMON MODE (V)

SENSE

BSENSE

= V

= 0V

+

– V

–

when

SENSE

= 5V

IN1

SENSE

–

= 0V

1473 G03

VGS Gate-to-Source ON Voltage
vs Temperature

6.0
V+ = V

= 10V

5.9

5.8

5.7

5.6

5.5

5.4

5.3

GATE-TO-SOURCE ON VOLTAGE (V)

GS

5.2

V

5.1

SAB

–60–40–20 204060800

TEMPERATURE (°C)

1473 G04

100

Undervoltage Lockout Threshold (V+)
vs Temperature

2.75

2.70

2.65

2.60

2.55

2.50

2.45

2.40

2.35

2.30

UNDERVOLTAGE LOCKOUT THRESHOLD (V)

2.25
–60

–40 0

START-UP

THRESHOLD

SHUTDOWN

THRESHOLD

–20

20

TEMPERATURE (°C)

40

VGS Gate Supply Voltage
vs Temperature

9.0
V+ = 5V

= VGG – V

V

8.9

GS

8.8

8.7

8.6

8.5

8.4

GATE SUPPLY VOLTAGE (V)

8.3

GS

V

8.2

80

60

100

1473 G05

8.1

–40–60

+

–20 20406080100

0

TEMPERATURE (°C)

1473 G06

3

LTC1473L

UW

TYPICAL PERFOR A CE CHARACTERISTICS

Turn-Off Delay and Gate Fall Time
vs Temperature

2.2

+

= 5V

V

= 1000pF

C

2.0

LOAD

V

= 5V

SAB

1.8

1.6

1.4

1.2

1.0

0.8

0.6

TURN-OFF DELAY AND GATE FALL TIME (µs)

0.4
–20 20406080100

–40–60

GATE FALL

TIME

TURN-OFF

DELAY

0

TEMPERATURE (°C)

Logic Input Threshold Voltage
vs Temperature

2.0

1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4

INPUT THRESHOLD VOLTAGE (V)

0.2
0

–60

–40 0

–20

TEMPERATURE (°C)

1473 G07

V+ = 10V

V+ = 2.8V

20

Turn-On Delay and Gate Rise Time
vs Temperature

45

+

= 5V

V

40
35
30
25
20
15
10

5

TURN-ON DELAY AND GATE RISE TIME (µs)

0

= 1000pF

C

LOAD

V

= 0V

SAB

–40 –20 20 40 60 80 100

–60

TEMPERATURE (°C)

GATE RISE

TIME

TURN-ON

DELAY

0

1473 G08

Rise and Fall Time
vs Gate Capacitive Loading

40
35
30
25
20
15
10

RISE AND FALL TIME (µs)

5
0

10

RISE TIME

= 0V

V

SAB

FALL TIME

= 5V

V

SAB

100 1000 10000

GATE CAPACITIVE LOADING (pF)

1473 G08

Timer Latch Threshold Voltage
vs Temperature

1.28
V+ = 5V

1.26

1.24

1.22

1.20

1.18

1.16

1.14

1.12

TIMER LATCH THRESHOLD VOLTAGE (V)

80

60

40

100

1473 G10

1.10

–25 25 50 75 100 125

–50

0
TEMPERATURE (°C)

1473 G11

4

Timer Source Current
vs Temperature

8.5
V+ = 5V

TIMER = 0V

8.0

7.5

7.0

6.5

6.0

5.5

5.0

TIMER SOURCE CURRENT (µA)

4.5

4.0

–25 25 50 75 100 125

–50

0
TEMPERATURE (°C)

1473 G12

SENSE Pin Source Current
(I

300

250

200

150

100

50

SENSE PIN CURRENT (µA)

0

–50

0

) vs V

BSENSE

123456789

SENSE

V+ = 5V
V
V
V

V

SENSE

DIODE

= 0V

IN2
SENSE

(V)

= V

+

– V

IN1

SENSE

= 5V

–

= 0V

10

1473 G13

UUU

PI FU CTIO S

LTC1473L

IN1 (Pin 1): Logic Input of Gate Drivers GA1 and GB1. IN1
is disabled when IN2 is high or DIODE is low. During
2-diode mode, asserting IN1 disables the fault timer
function.

IN2 (Pin 2): Logic Input of Gate Drivers GA2 and GB2. IN2
is disabled when IN1 is high or DIODE is low. During
2-diode mode, asserting IN2 disables the fault timer
function.

DIODE (Pin 3): “2-Diode Mode” Logic Input. Diode over­rides IN1 and IN2 by forcing the two back-to-back
external N-channel MOSFET switches to mimic two di­odes.

TIMER (Pin 4): Fault Timer. A capacitor connected from
this pin to GND programs the time the MOSFET switches
are allowed to be in current limit. To disable this function,
Pin 4 can be grounded.

V+ (Pin 5): Power Supply. Bypass this pin with at least a
1µF capacitor.

VGG (Pin 6): Gate Driver Supply. This high voltage supply
is intended only for driving the internal micropower gate
drive circuitry.

circuitry

. Bypass this pin with at least 1µF.

Do not load this pin with any external

SW (Pin 7): Open Drain of an Internal N-Channel MOSFET
Switch. This pin drives the bottom of the VGG switching
regulator inductor which is connected between this pin and
the V+ pin.

GND (Pin 8): Ground.
GB2, GA2 (Pins 9, 11): Switch Gate Drivers. GA2 and GB2

drive the gates of the second back-to-back external
N-channel switches.

SAB2 (Pin 10): Source Return. The SAB2 pin is connected
to the sources of SW A2 and SW B2. A small pull-down
current source returns this node to 0V when the switches
are turned off.

SENSE– (Pin 12): Inrush Current Input. This pin should be
connected directly to the bottom (output side) of the low
valued resistor in series with the two input power selector
switch pairs, SW A1/B1 and SW A2/B2, for detecting and
controlling the inrush current into and out of the power
supply sources and the output capacitor.

SENSE+ (Pin 13): Inrush Current Input. This pin should be
connected directly to the top (switch side) of the low
valued resistor in series with the two input power selector
switch pairs, SW A1/B1 and SW A2/B2, for detecting and
controlling the inrush current into and out of the power
supply sources and the output capacitor. Current limit is
invoked when (V

Pin Function Table

PIN NAME DESCRIPTION MIN TYP MAX MIN MAX

1 IN1 Logic Input of Gate Drivers GA1 and GB1 0.4 1 2 –0.3 7
2 IN2 Logic Input of Gate Drivers GA2 and GB2 0.4 1 2 –0.3 7
3 DIODE “2-Diode Mode” Logic Input 0.4 1 2 –0.3 7
4 TIMER Fault Timer Programs Time in Current Limit 1.16 –0.3 5
5V+Power Supply 2.8 9 –0.3 10
6VGGGate Driver Supply 10.2 20 –0.3 20
7 SW Switch Node of Internal Boost Switching Regulator 0 20 –0.3 20
8 GND Ground 0 0 0
9 GB2 Switch Gate Driver for Switch B2 0 17 –0.3 20
10 SAB2 Source Return of Switch 2 0 10 –0.3 10
11 GA2 Switch Gate Driver for Switch A2 0 17 –0.3 20
12 SENSE
13 SENSE
14 GB1 Switch Gate Driver for Switch B1 0 17 –0.3 20
15 SAB1 Source Return of Switch 1 0 10 –0.3 10
16 GA1 Switch Gate Driver for Switch A1 0 17 –0.3 20

–

Inrush Current Input, Low Side 0 10 –0.3 10

+

Inrush Current Input, High Side 0 10 –0.3 10

NOMINAL (V) ABSOLUTE MAX (V)

SENSE

+

– V

SENSE

–

) exceeds ±0.2V.

5