TPS2041, TPS2051
POWER-DISTRIBUTION SWITCHES
SLVS172A –AUGUST 1998 – REVISED APRIL 1999
D
D
D
D
D
D
D
D
D
D
D
D
D
135-mΩ -Maximum (5-V Input) High-Side
MOSFET Switch
500 mA Continuous Current
Short-Circuit and Thermal Protection With
Overcurrent Logic Output
Operating Range . . . 2.7 V to 5.5 V
Logic-Level Enable Input
2.5-ms Typical Rise Time
Undervoltage Lockout
10 µA Maximum Standby Supply Current
Bidirectional Switch
Available in 8-pin SOIC and PDIP Packages
Ambient Temperature Range, –40°C to 85°C
2-kV Human-Body-Model, 200-V
Machine-Model ESD Protection
UL Listed – File No. E169910
TPS2041
D OR P PACKAGE
(TOP VIEW)
GND
IN
IN
EN
1
8
2
7
3
6
4
5
OUT
OUT
OUT
OC
TPS2051
D OR P PACKAGE
(TOP VIEW)
GND
IN
IN
EN
1
8
2
7
3
6
4
5
OUT
OUT
OUT
OC
description
The TPS2041 and TPS2051 power distribution switches are intended for applications where heavy capacitive
loads and short circuits are likely to be encountered. The TPS2041 and the TPS2051 are 135-mΩ N-channel
MOSFET high-side power switches. Each switch is controlled by a logic enable compatible with 5-V and 3-V
logic. Gate drive is provided by an internal charge pump that controls the power-switch rise times and fall times
to minimize current surges during switching. The charge pump requires no external components and allows
operation from supplies as low as 2.7 V.
When the output load exceeds the current-limit threshold or a short is present, the TPS2041 and TPS2051 limit
the output current to a safe level by switching into a constant-current mode, pulling the overcurrent (OC) logic
output low. When continuous heavy overloads and short circuits increase the power dissipation in the switch,
causing the junction temperature to rise, a thermal protection circuit shuts off the switch in overcurrent to prevent
damage. Recovery from a thermal shutdown is automatic once the device has cooled sufficiently. Internal
circuitry ensures the switch remains off until valid input voltage is present.
The TPS2041 and TPS2051 are designed to limit at 0.9-A load. These power distribution switches are available
in 8-pin small-outline integrated circuit (SOIC) and 8-pin plastic dual-in-line packages (PDIP) and operate over
an ambient temperature range of –40°C to 85°C.
AVAILABLE OPTIONS
TA
ENABLE
RECOMMENDED
MAXIMUM CONTINUOUS
LOAD CURRENT
(A)
TYPICAL SHORT-CIRCUIT
CURRENT LIMIT AT 25°C
(A)
–40°C to 85°C
Active low
0.5
–40°C to 85°C
Active high
0.5
PACKAGED DEVICES
SOIC
(D)†
PDIP
(P)
0.9
TPS2041D
TPS2041P
0.9
TPS2051D
TPS2051P
† The D package is available taped and reeled. Add an R suffix to device type (e.g., TPS2041DR)
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
Copyright 1999, Texas Instruments Incorporated
This document contains information on products in more than one phase
of development. The status of each device is indicated on the page(s)
specifying its electrical characteristics.
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
1
TPS2041, TPS2051
POWER-DISTRIBUTION SWITCHES
SLVS172A –AUGUST 1998 – REVISED APRIL 1999
TPS2041 functional block diagram
Power Switch
†
CS
IN
OUT
Charge
Pump
EN
Driver
Current
Limit
OC
UVLO
Thermal
Sense
GND
†Current Sense
Terminal Functions
TERMINAL
NO.
NAME
I/O
D OR P
DESCRIPTION
TPS2041
TPS2051
EN
4
–
I
Enable input. Logic low turns on power switch.
EN
–
4
I
Enable input. Logic high turns on power switch.
GND
1
1
I
Ground
IN
2, 3
2, 3
I
Input voltage
OC
5
5
O
Over current. Logic output active low
6, 7, 8
6, 7, 8
O
Power-switch output
OUT
2
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
TPS2041, TPS2051
POWER-DISTRIBUTION SWITCHES
SLVS172A –AUGUST 1998 – REVISED APRIL 1999
detailed description
power switch
The power switch is an N-channel MOSFET with a maximum on-state resistance of 135 mΩ (VI(IN) = 5 V).
Configured as a high-side switch, the power switch prevents current flow from OUT to IN and IN to OUT when
disabled. The power switch supplies a minimum of 500 mA per switch.
charge pump
An internal charge pump supplies power to the driver circuit and provides the necessary voltage to pull the gate
of the MOSFET above the source. The charge pump operates from input voltages as low as 2.7 V and requires
very little supply current.
driver
The driver controls the gate voltage of the power switch. To limit large current surges and reduce the associated
electromagnetic interference (EMI) produced, the driver incorporates circuitry that controls the rise times and
fall times of the output voltage. The rise and fall times are typically in the 2-ms to 4-ms range.
enable (EN or EN)
The logic enable disables the power switch and the bias for the charge pump, driver, and other circuitry to reduce
the supply current to less than 10 µA when a logic high is present on EN (TPS2041) or a logic low is present
on EN (TPS2051). A logic zero input on EN or a logic high on EN restores bias to the drive and control circuits
and turns the power on. The enable input is compatible with both TTL and CMOS logic levels.
overcurrent (OC)
The OC open drain output is asserted (active low) when an overcurrent or overtemperature condition is
encountered. The output will remain asserted until the overcurrent or overtemperature condition is removed.
current sense
A sense FET monitors the current supplied to the load. The sense FET measures current more efficiently than
conventional resistance methods. When an overload or short circuit is encountered, the current-sense circuitry
sends a control signal to the driver. The driver in turn reduces the gate voltage and drives the power FET into
its saturation region, which switches the output into a constant current mode and holds the current constant
while varying the voltage on the load.
thermal sense
An internal thermal-sense circuit shuts off the power switch when the junction temperature rises to
approximately 140°C. Hysteresis is built into the thermal sense circuit. After the device has cooled
approximately 20°C, the switch turns back on. The switch continues to cycle off and on until the fault is removed.
undervoltage lockout
A voltage sense circuit monitors the input voltage. When the input voltage is below approximately 2 V, a control
signal turns off the power switch.
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
3
TPS2041, TPS2051
POWER-DISTRIBUTION SWITCHES
SLVS172A –AUGUST 1998 – REVISED APRIL 1999
absolute maximum ratings over operating free-air temperature range (unless otherwise noted)†
Input voltage range, VI(IN) (see Note 1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to 6 V
Output voltage range, VO(OUT) (see Note 1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to VI(IN) + 0.3 V
Input voltage range, VI(ENx) or VI(ENx) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to 6 V
Continuous output current, IO(OUT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . internally limited
Continuous total power dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See Dissipation Rating Table
Operating virtual junction temperature range, TJ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –40°C to 125°C
Storage temperature range, Tstg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –65°C to 150°C
Lead temperature soldering 1,6 mm (1/16 inch) from case for 10 seconds . . . . . . . . . . . . . . . . . . . . . . . 260°C
Electrostatic discharge (ESD) protection: Human body model MIL-STD-883C . . . . . . . . . . . . . . . . . . . . . 2 kV
Machine model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.2 kV
† Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only, and
functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is not
implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
NOTE 1: All voltages are with respect to GND.
DISSIPATION RATING TABLE
PACKAGE
TA ≤ 25°C
POWER RATING
DERATING FACTOR
ABOVE TA = 25°C
TA = 70°C
POWER RATING
TA = 85°C
POWER RATING
D
725 mW
5.8 mW/°C
464 mW
377 mW
P
1175 mW
9.4 mW/°C
752 mW
611 mW
recommended operating conditions
Input voltage, VI(IN)
TPS2041
TPS2051
MIN
MAX
MIN
MAX
2.7
5.5
2.7
5.5
UNIT
V
Input voltage, VI(EN) or VI(EN)
0
5.5
0
5.5
V
Continuous output current, IO(OUT)
0
500
0
500
mA
–40
125
–40
125
°C
Operating virtual junction temperature, TJ
4
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
TPS2041, TPS2051
POWER-DISTRIBUTION SWITCHES
SLVS172A –AUGUST 1998 – REVISED APRIL 1999
electrical characteristics over recommended operating junction temperature range, VI(IN)= 5.5 V,
IO = rated current, VI(EN) = 0 V, VI(EN) = Hi (unless otherwise noted)
power switch
TEST CONDITIONS†
PARAMETER
Static
St
ti drain-source
d i
on-state
t t
resistance 5-V o
resistance,
operation
eration
rDS(on)
DS( )
Static
St
ti drain-source
d i
on-state
t t
resistance,
o eration
resistance 3.3-V
3 3-V operation
tr
tf
Rise time
time, output
Fall time,
time output
TPS2041
MIN
TYP
TPS2051
MAX
MIN
TYP
MAX
VI(IN) = 5 V,
VI(IN) = 5 V,
TJ = 25°C
TJ = 85°C
80
95
80
95
90
120
90
120
VI(IN) = 5 V,
VI(IN) = 3.3 V,
TJ = 125°C
TJ = 25°C
100
135
100
135
85
105
85
105
VI(IN) = 3.3 V,
VI(IN) = 3.3 V,
TJ = 85°C
TJ = 125°C
100
135
100
135
115
150
115
150
VI(IN) = 5.5 V,
CL = 1 µF,
TJ = 25°C,
RL = 10 Ω
2.5
2.5
VI(IN) = 2.7 V,
CL = 1 µF,
TJ = 25°C,
RL = 10 Ω
3
3
VI(IN) = 5.5 V,
CL = 1 µF,
VI(IN) = 2.7 V,
CL = 1 µF,
TJ = 25°C,
RL = 10 Ω
TJ = 25°C,
RL = 10 Ω
4.4
4.4
2.5
2.5
UNIT
mΩ
ms
ms
† Pulse-testing techniques maintain junction temperature close to ambient temperature; thermal effects must be taken into account separately.
enable input EN or EN
PARAMETER
VIH
VIL
TEST CONDITIONS
2.7 V ≤ VI(IN) ≤ 5.5 V
High-level input voltage
Low level input voltage
Low-level
II
Input current
ton
toff
Turnon time
TPS2041
TPS2051
Turnoff time
TPS2041
MIN
TYP
TPS2051
MAX
2
MIN
TYP
MAX
2
V
4.5 V ≤ VI(IN) ≤ 5.5 V
0.8
0.8
2.7 V ≤ VI(IN) ≤ 4.5 V
0.4
0.4
VI(EN) = 0 V or VI(EN) = VI(IN)
VI(EN) = VI(IN) or VI(EN) = 0 V
–0.5
0.5
–0.5
CL = 100 µF, RL = 10 Ω
CL = 100 µF, RL = 10 Ω
UNIT
0.5
20
20
40
40
V
µA
ms
current limit
PARAMETER
IOS
Short-circuit output current
TPS2041
TEST CONDITIONS†
MIN
VI(IN) = 5 V, OUT connected to GND,
Device enabled into short circuit
TYP
0.7
0.9
TPS2051
MAX
MIN
1.1
0.7
TYP
0.9
MAX
1.1
UNIT
A
† Pulse-testing techniques maintain junction temperature close to ambient temperature; thermal effects must be taken into account separately.
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
5
TPS2041, TPS2051
POWER-DISTRIBUTION SWITCHES
SLVS172A –AUGUST 1998 – REVISED APRIL 1999
electrical characteristics over recommended operating junction temperature range, VI(IN)= 5.5 V,
IO = rated current, VI(EN) = 0 V, VI(EN) = Hi (unless otherwise noted) (continued)
supply current
PARAMETER
TPS2041
TEST CONDITIONS
Supply
y current,,
low-level output
EN = VI(IN)
TJ = 25°C
–40°C ≤ TJ ≤ 125°C
TPS2041
EN = 0 V
TJ = 25°C
–40°C ≤ TJ ≤ 125°C
TPS2051
EN = 0 V
TJ = 25°C
–40°C ≤ TJ ≤ 125°C
EN = VI(IN)
TJ = 25°C
–40°C ≤ TJ ≤ 125°C
TPS2051
OUT
connected
to ground
EN = VI(IN)
–40°C ≤ TJ ≤ 125°C
TPS2041
EN= 0 V
–40°C ≤ TJ ≤ 125°C
TPS2051
IN = High
g
impedance
VI(EN) = 0 V
VI(EN) = Hi
TJ = 25°C
No Load
on OUT
Supply
y current,,
high-level output
No Load
on OUT
Leakage current
Reverse leakage
g
current
MIN
TYP
TPS2051
MAX
0.015
MIN
TYP
MAX
0.015
1
UNIT
1
10
µA
10
80
TPS2041
100
100
80
100
µA
100
100
µA
100
TPS2041
0.3
TPS2051
µA
0.3
undervoltage lockout
PARAMETER
TEST CONDITIONS
Low-level input voltage
Hysteresis
TPS2041
MIN
TYP
2
TJ = 25°C
TPS2051
MAX
MIN
2.5
2
100
TYP
MAX
2.5
100
UNIT
V
mV
overcurrent OC
PARAMETER
Sink current†
Output low voltage
Off-state current†
TEST CONDITIONS
VO = 5 V
IO = 5 V,
VOL(OC)
VO = 5 V,
VO = 3.3 V
TPS2041
MIN
† Specified by design, not production tested.
6
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
TYP
TPS2051
MAX
MIN
TYP
MAX
UNIT
10
10
mA
0.5
0.5
V
1
1
µA
TPS2041, TPS2051
POWER-DISTRIBUTION SWITCHES
SLVS172A –AUGUST 1998 – REVISED APRIL 1999
PARAMETER MEASUREMENT INFORMATION
OUT
RL
tf
tr
CL
VO(OUT)
90%
10%
90%
10%
TEST CIRCUIT
50%
VI(EN)
50%
toff
ton
toff
ton
90%
VO(OUT)
50%
50%
VI(EN)
90%
VO(OUT)
10%
10%
VOLTAGE WAVEFORMS
Figure 1. Test Circuit and Voltage Waveforms
VI(EN)
(5 V/div)
VI(EN)
(5 V/div)
VI(IN) = 5 V
TA = 25°C
CL = 0.1 µF
VO(OUT)
(2 V/div)
0
1
2
3
4
5
6
7
8
9
VI(IN) = 5 V
TA = 25°C
CL = 0.1 µF
VO(OUT)
(2 V/div)
10
0
1000
2000
3000
4000
5000
t – Time – ms
t – Time – ms
Figure 2. Turnon Delay and Rise Time
with 0.1-µF Load
POST OFFICE BOX 655303
Figure 3. Turnoff Delay and Fall Time
with 0.1-µF Load
• DALLAS, TEXAS 75265
7
TPS2041, TPS2051
POWER-DISTRIBUTION SWITCHES
SLVS172A –AUGUST 1998 – REVISED APRIL 1999
PARAMETER MEASUREMENT INFORMATION
VI(EN)
(5 V/div)
VI(EN)
(5 V/div)
VI(IN) = 5 V
TA = 25°C
CL = 1 µF
RL = 10 Ω
VO(OUT)
(2 V/div)
0
1
2
3
4
5
6
7
8
VI(IN) = 5 V
TA = 25°C
CL = 1 µF
RL = 10 Ω
VO(OUT)
(2 V/div)
9
10
0
2
4
6
t – Time – ms
8
10
12
14
16
18
20
t – Time – ms
Figure 4. Turnon Delay and Rise Time
with 1-µF Load
Figure 5. Turnoff Delay and Fall Time
with 1-µF Load
VI(IN) = 5 V
TA = 25°C
VI(IN) = 5 V
TA = 25°C
VI(EN)
(5 V/div)
VO(OUT)
(2 V/div)
IO(OUT)
(0.5 A/div)
IO(OUT)
(0.2 A/div)
0
1
2
3
4
5
6
7
8
9
10
0
10
Figure 6. TPS2041, Short-Circuit Current,
Device Enabled into Short
8
20
30
40
50
60
70
80
90 100
t – Time – ms
t – Time – ms
POST OFFICE BOX 655303
Figure 7. TPS2041, Threshold Trip Current
with Ramped Load on Enabled Device
• DALLAS, TEXAS 75265
TPS2041, TPS2051
POWER-DISTRIBUTION SWITCHES
SLVS172A –AUGUST 1998 – REVISED APRIL 1999
PARAMETER MEASUREMENT INFORMATION
VI(IN) = 5 V
TA = 25°C
RL = 10 Ω
VI(EN)
(5 V/div)
VO(OC)
(5 V/div)
470 µF
220 µF
100 µF
VI(IN) = 5 V
Load Ramp,1A/100 ms
TA = 25°C
IO(OUT)
(0.5 A/div)
IO(OUT)
(o.2 A/div)
0
2
4
6
8
10
12
14
16
0
18 20
20
40
60
80 100 120 140 160 180 200
t – Time – ms
t – Time – ms
Figure 8. Inrush Current with 100-µF, 220-µF
and 470-µF Load Capacitance
Figure 9. Ramped Load on Enabled Device
VI(IN) = 5 V
TA = 25°C
VI(IN) = 5 V
TA = 25°C
VO(OC)
(5 V/div)
VO(OC)
(5 V/div)
IO(OUT)
(0.5 A/div)
IO(OUT)
(1 A/div)
0
400
800
1200
1600
2000
0
20
t – Time – µs
40
60
80 100 120 140 160 180 200
t – Time – µs
Figure 10. 4-Ω Load Connected to Enabled Device
POST OFFICE BOX 655303
Figure 11. 1-Ω Load Connected
to Enabled Device
• DALLAS, TEXAS 75265
9
TPS2041, TPS2051
POWER-DISTRIBUTION SWITCHES
SLVS172A –AUGUST 1998 – REVISED APRIL 1999
TYPICAL CHARACTERISTICS
TURNON DELAY
vs
INPUT VOLTAGE
TURNOFF DELAY
vs
INPUT VOLTAGE
6
17
CL = 1 µF
RL = 10 Ω
TA = 25°C
5.5
16
CL = 1 µF
RL = 10 Ω
TA = 25°C
Turn-Off Delay – ms
Turn-On Delay – ms
15
5
4.5
4
14
13
12
11
3.5
3
2.5
10
3
3.5
4
4.5
5
5.5
3
2.5
6
3
VI – Input Voltage – V
5
3.5
4
4.5
VI – Input Voltage – V
Figure 12
3.3
f t – Fall Time – ms
r t – Rise Time – ms
0.9
3.5
VI(IN) = 5 V
CL = 1 µF
TA = 25°C
2.8
2.7
2.6
VI(IN) = 5 V
TA = 25°C
CL = 1 µF
3.1
2.9
2.7
0.2
0.3
0.4 0.5 0.6
0.7
IL – Load Current – A
0.8
0.9
2.5
0.1
0.2
Figure 14
10
0.8
FALL TIME
vs
LOAD CURRENT
3
2.5
0.1
6
Figure 13
RISE TIME
vs
LOAD CURRENT
2.9
5.5
0.3
0.4
0.5
0.6
0.7
IL – Load Current – A
Figure 15
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
TPS2041, TPS2051
POWER-DISTRIBUTION SWITCHES
SLVS172A –AUGUST 1998 – REVISED APRIL 1999
TYPICAL CHARACTERISTICS
SUPPLY CURRENT, OUTPUT ENABLED
vs
JUNCTION TEMPERATURE
SUPPLY CURRENT, OUTPUT DISABLED
vs
JUNCTION TEMPERATURE
1000
I I(IN) – Supply Current, Output Disabled – nA
I I(IN) – Supply Current, Output Enabled – µ A
100
VI(IN) = 5.5 V
VI(IN) = 5 V
90
VI(IN) = 4 V
80
VI(IN) = 2.7 V
70
VI(IN) = 3.3 V
60
50
–50
–25
75 100 125
0
25
50
TJ – Junction Temperature – °C
900
700
VI(IN) = 4 V
600
500
VI(IN) = 2.7 V
400
300
200
100
0
–100
–50
150
VI(IN) = 5.5 V
VI(IN) = 5 V
800
–25
Figure 16
SUPPLY CURRENT, OUTPUT DISABLED
vs
INPUT VOLTAGE
1000
– Supply Current, Output Disabled – nA
I I(IN)
100
I I(IN) – Supply Current, Output Enabled – µ A
150
Figure 17
SUPPLY CURRENT, OUTPUT ENABLED
vs
INPUT VOLTAGE
TJ = 125°C
90
TJ = 85°C
80
TJ = 25°C
70
TJ = 0°C
TJ = –40°C
60
50
2.5
100 125
0
25
50
75
TJ – Junction Temperature – °C
3
3.5
4
4.5
5
5.5
6
TJ = 125°C
800
600
400
200
TJ = 85°C
TJ = 25°C
0
TJ = –40°C
–200
2.5
3
VI – Input Voltage – V
3.5
4
4.5
5
VI – Input Voltage – V
TJ = 0°C
5.5
6
Figure 19
Figure 18
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
11
TPS2041, TPS2051
POWER-DISTRIBUTION SWITCHES
SLVS172A –AUGUST 1998 – REVISED APRIL 1999
STATIC DRAIN-SOURCE ON-STATE RESISTANCE
vs
JUNCTION TEMPERATURE
175
IO = 0.5 A
VI(IN) = 2.7 V
150
VI(IN) = 3.3 V
125
100
VI(IN) = 4.5 V
VI(IN) = 5 V
75
50
–50
–25
0
25
50
100
75
125
150
r DS(on) – Static Drain-Source On-State Resistance – mΩ
r DS(on) – Static Drain-Source On-State Resistance – m Ω
TYPICAL CHARACTERISTICS
STATIC DRAIN-SOURCE ON-STATE RESISTANCE
vs
INPUT VOLTAGE
175
IO = 0.5 A
150
TJ = 125°C
125
TJ = 85°C
100
TJ = 25°C
75
TJ = 0°C
TJ = –40°C
50
2.5
3
TJ – Junction Temperature – °C
Figure 20
6
SHORT-CURCUIT OUTPUT CURRENT
vs
INPUT VOLTAGE
100
0.95
TA = 25°C
I OS – Short-circuit Output Current – A
VI(IN) – VO(OUT) – Input-to-Output Voltage – mV
5.5
Figure 21
INPUT-TO-OUTPUT VOLTAGE
vs
LOAD CURRENT
75
VI(IN) = 2.7 V
VI(IN) = 3.3 V
50
VI(IN) = 5 V
25
VI(IN) = 4.5 V
0
0.1
0.2
0.4
0.5
0.6
TJ = –40°C
0.9
TJ = 25°C
TJ = 125°C
0.85
0.8
2.5
3
IL – Load Current – A
Figure 22
12
3.5
4
4.5
5
VI – Input Voltage – V
4.5
5
3.5
4
VI – Input Voltage – V
Figure 23
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5.5
6
TPS2041, TPS2051
POWER-DISTRIBUTION SWITCHES
SLVS172A –AUGUST 1998 – REVISED APRIL 1999
TYPICAL CHARACTERISTICS
THRESHOLD TRIP CURRENT
vs
INPUT VOLTAGE
SHORT CIRCUIT OUTPUT CURRENT
vs
JUNCTION TEMPERATURE
1.2
0.95
I OS – Short-circuit Output Current – A
Threshold Trip Current – A
TA = 25°C
Load Ramp = 1 A/10 ms
1.175
1.15
1.125
1.1
2.5
3
4.5
5
3.5
4
VI – Input Voltage – V
5.5
VI(IN) = 5 V
0.9
VI(IN) = 4 V
VI(IN) = 2.7 V
0.85
0.8
–50
6
–25
75
100
0
25
50
TJ – Junction Temperature – °C
Figure 24
Figure 25
UNDERVOLTAGE LOCKOUT
vs
JUNCTION TEMPERATURE
CURRENT LIMIT RESPONSE
vs
PEAK CURRENT
2.5
500
VI(IN) = 5 V
TA = 25°C
450
2.4
Current Limit Response – µ s
UVLO – Undervoltage Lockout – V
125
Start Threshold
2.3
Stop Threshold
2.2
2.1
400
350
300
250
200
150
100
50
2
–50
0
–25
100 125
0
25
50
75
TJ – Junction Temperature – °C
150
0
2.5
5
7.5
10
12.5
Peak Current – A
Figure 26
Figure 27
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TPS2041, TPS2051
POWER-DISTRIBUTION SWITCHES
SLVS172A –AUGUST 1998 – REVISED APRIL 1999
TYPICAL CHARACTERISTICS
OVERCURRENT RESPONSE TIME (OC)
vs
PEAK CURRENT
8
VI(IN) = 5 V
TA = 25°C
Response Time – µ s
6
4
2
0
0
2.5
5
7.5
10
12.5
Peak Current – A
Figure 28
APPLICATION INFORMATION
TPS2041
Power Supply
2.7 V to 5.5 V
2,3
IN
0.1 µF
OUT
6,7,8
Load
0.1 µF
5
4
22 µF
OC
EN
GND
1
Figure 29. Typical Application
power-supply considerations
A 0.01-µF to 0.1-µF ceramic bypass capacitor between INx and GND, close to the device, is recommended.
Placing a high-value electrolytic capacitor on the output pin(s) is recommended when the output load is heavy.
This precaution reduces power-supply transients that may cause ringing on the input. Additionally, bypassing
the output with a 0.01-µF to 0.1-µF ceramic capacitor improves the immunity of the device to short-circuit
transients.
14
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TPS2041, TPS2051
POWER-DISTRIBUTION SWITCHES
SLVS172A –AUGUST 1998 – REVISED APRIL 1999
APPLICATION INFORMATION
overcurrent
A sense FET is employed to check for overcurrent conditions. Unlike current-sense resistors, sense FETs do
not increase the series resistance of the current path. When an overcurrent condition is detected, the device
maintains a constant output current and reduces the output voltage accordingly. Complete shutdown occurs
only if the fault is present long enough to activate thermal limiting.
Three possible overload conditions can occur. In the first condition, the output has been shorted before the
device is enabled or before VI(IN) has been applied (see Figure 6). The TPS2041 and TPS2051 sense the short
and immediately switch into a constant-current output.
In the second condition, the short occurs while the device is enabled. At the instant the short occurs, very high
currents may flow for a short time before the current-limit circuit can react. After the current-limit circuit has
tripped (reached the overcurrent trip threshhold) the device switches into constant-current mode.
In the third condition, the load has been gradually increased beyond the recommended operating current. The
current is permitted to rise until the current-limit threshold is reached or until the thermal limit of the device is
exceeded (see Figure 7). The TPS2041 and TPS2051 are capable of delivering current up to the current-limit
threshold without damaging the device. Once the threshold has been reached, the device switches into its
constant-current mode.
OC response
The OC open-drain output is asserted (active low) when an overcurrent or overtemperature condition is
encountered. The output will remain asserted until the overcurrent or overtemperature condition is removed.
Connecting a heavy capacitive load to an enabled device can cause momentary false overcurrent reporting from
the inrush current flowing through the device, charging the downstream capacitor. An RC filter of 500 µs (see
Figure 30) can be connected to the OC pin to reduce false overcurrent reporting. Using low-ESR electrolytic
capacitors on the output lowers the inrush current flow through the device during hot-plug events by providing
a low-impedance energy source, thereby reducing erroneous overcurrent reporting.
TPS2041
TPS2041
GND
OUT
IN
OUT
IN
OUT
EN
V+
Rpullup
GND
OUT
IN
OUT
IN
OUT
EN
OC
V+
OC
Rpullup
Rfilter
To USB
Controller
Cfilter
Figure 30. Typical Circuit for OC Pin and RC Filter for Damping Inrush OC Responses
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TPS2041, TPS2051
POWER-DISTRIBUTION SWITCHES
SLVS172A –AUGUST 1998 – REVISED APRIL 1999
APPLICATION INFORMATION
power dissipation and junction temperature
The low on-resistance on the n-channel MOSFET allows small surface-mount packages, such as SOIC, to pass
large currents. The thermal resistances of these packages are high compared to those of power packages; it
is good design practice to check power dissipation and junction temperature. The first step is to find rDS(on) at
the input voltage and operating temperature. As an initial estimate, use the highest operating ambient
temperature of interest and read rDS(on) from Figure 21. Next, calculate the power dissipation using:
PD
+ rDS(on)
I2
Finally, calculate the junction temperature:
TJ
Where:
+ PD
R qJA
) TA
TA = Ambient Temperature °C
RθJA = Thermal resistance SOIC = 172°C/W, PDIP = 106°C/W
Compare the calculated junction temperature with the initial estimate. If they do not agree within a few degrees,
repeat the calculation, using the calculated value as the new estimate. Two or three iterations are generally
sufficient to get a reasonable answer.
thermal protection
Thermal protection prevents damage to the IC when heavy-overload or short-circuit faults are present for
extended periods of time. The faults force the TPS2041 and TPS2051 into constant current mode, which causes
the voltage across the high-side switch to increase; under short-circuit conditions, the voltage across the switch
is equal to the input voltage. The increased dissipation causes the junction temperature to rise to high levels.
The protection circuit senses the junction temperature of the switch and shuts it off. Hysteresis is built into the
thermal sense circuit, and after the device has cooled approximately 20 degrees, the switch turns back on. The
switch continues to cycle in this manner until the load fault or input power is removed.
undervoltage lockout (UVLO)
An undervoltage lockout ensures that the power switch is in the off state at powerup. Whenever the input voltage
falls below approximately 2 V, the power switch will be quickly turned off. This facilitates the design of
hot-insertion systems where it is not possible to turn off the power switch before input power is removed. The
UVLO will also keep the switch from being turned on until the power supply has reached at least 2 V, even if
the switch is enabled. Upon reinsertion, the power switch will be turned on, with a controlled rise time to reduce
EMI and voltage overshoots.
universal serial bus (USB) applications
The universal serial bus (USB) interface is a 12-Mb/s, or 1.5-Mb/s, multiplexed serial bus designed for
low-to-medium bandwidth PC peripherals (e.g., keyboards, printers, scanners, and mice). The four-wire USB
interface is conceived for dynamic attach-detach (hot plug-unplug) of peripherals. Two lines are provided for
differential data, and two lines are provided for 5-V power distribution.
USB data is a 3.3-V level signal, but power is distributed at 5 V to allow for voltage drops in cases where power
is distributed through more than one hub across long cables. Each function must provide its own regulated 3.3 V
from the 5-V input or its own internal power supply.
16
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TPS2041, TPS2051
POWER-DISTRIBUTION SWITCHES
SLVS172A –AUGUST 1998 – REVISED APRIL 1999
APPLICATION INFORMATION
The USB specification defines the following five classes of devices, each differentiated by power-consumption
requirements:
D
D
D
D
D
Hosts/self-powered hubs (SPH)
Bus-powered hubs (BPH)
Low-power, bus-powered functions
High-power, bus-powered functions
Self-powered functions
Self-powered and bus-powered hubs distribute data and power to downstream functions. The TPS2041 and
TPS2051 can provide power-distribution solutions for many of these classes of devices.
host/self-powered and bus-powered hubs
Hosts and self-powered hubs have a local power supply that powers the embedded functions and the
downstream ports (see Figure 31). This power supply must provide from 5.25 V to 4.75 V to the board side of
the downstream connection under full-load and no-load conditions. Hosts and SPHs are required to have
current limit protection and must report overcurrent conditions to the USB controller. Typical SPHs are desktop
PCs, monitors, printers, and stand-alone hubs.
Power Supply
3.3 V
Downstream
USB Ports
5V
TPS2041
2, 3
IN
0.1 µF
†
USB
Control
D+
OUT
D–
7
0.1 µF
5
4
120 µF
VBUS
GND
OC
EN
GND
† May need RC Filter (see Figure 34)
Figure 31. One-Port Solution
Bus-powered hubs obtain all power from upstream ports and often contain an embedded function. The hubs
are required to power up with less than one unit load. The BPH usually has one embedded function, and power
is always available to the controller of the hub. If the embedded function and hub require more than 100 mA
on powerup, the power to the embedded function may need to be kept off until enumeration is completed. This
can be accomplished by removing power or by shutting off the clock to the embedded function. Power switching
the embedded function is not necessary if the aggregate power draw for the function and controller is less than
one unit load. The total current drawn by the bus-powered device is the sum of the current to the controller, the
embedded function, and the downstream ports, and it is limited to 500 mA from an upstream port.
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TPS2041, TPS2051
POWER-DISTRIBUTION SWITCHES
SLVS172A –AUGUST 1998 – REVISED APRIL 1999
APPLICATION INFORMATION
low-power bus-powered functions and high-power bus-powered functions
Both low-power and high-power bus-powered functions obtain all power from upstream ports; low-power
functions always draw less than 100 mA; high-power functions must draw less than 100 mA at powerup and
can draw up to 500 mA after enumeration. If the load of the function is more than the parallel combination of
44 Ω and 10 µF at powerup, the device must implement inrush current limiting (see Figure 32).
Power Supply
D+
3.3 V
TPS2041
D–
VBUS
GND
2,3
0.1 µF
10 µF
IN
OUT
6, 7, 8
0.1 µF
5
USB
Control
4
10 µF
Internal
Function
OC
EN
GND
1
Figure 32. High-Power Bus-Powered Function
USB power-distribution requirements
USB can be implemented in several ways, and, regardless of the type of USB device being developed, several
powe- distribution features must be implemented.
D
D
D
Hosts/self-powered hubs must:
–
Current-limit downstream ports
–
Report overcurrent conditions on USB VBUS
Bus-powered hubs must:
–
Enable/disable power to downstream ports
–
Power up at
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