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TPS2561A-Q1
SLVSCC6A – MARCH 2014 – REVISED JUNE 2014
TPS2561A-Q1 Dual Channel Precision Automotive Adjustable
Current-Limited Power Switches
1 Features
3 Description
•
The TPS2561A-Q1 is dual-channel power-distribution
switch intended for automotive applications where
precision current limiting is required or heavy
capacitive loads and short circuits are encountered.
These devices offer a programmable current-limit
threshold between 250 mA and 2.8 A (typ) per
channel via an external resistor. The power-switch
rise and fall times are controlled to minimize current
surges during turn on/off.
1
•
•
•
•
•
•
•
•
•
•
AEC-Q100 Qualified
– Device HBM ESD Classification Level H2
– Device CDM ESD Classification Level C5
Two separate current limiting channels
Meets USB Current-Limiting Requirements
Adjustable Current Limit, 250 mA–2.8 A (Typ.)
Accurate 2.1A Min / 2.5A Max Setting
Fast Short Circuit Response - 3.5-μs (typ)
Two 44-mΩ High-Side MOSFETs
Operating Range: 2.5 V to 6.5 V
2-μA Maximum Standby Supply Current
Built-in Soft-Start
15 kV / 8 kV System-Level ESD Capable
Each channel of the TPS2561A-Q1 devices limits the
output current to a safe level by switching into a
constant-current mode when the output load exceeds
the current-limit threshold. The FAULTx logic output
for each channel independently asserts low during
overcurrent and over temperature conditions.
Use with the TPS2511-Q or TPS2513A-Q1 for a low
loss, automotive qualified, USB Charging Port
Solution capable of charging all of today's popular
phones and tablets.
2 Applications
Automotive USB Charging Ports
Device Information
PART NUMBER
PACKAGE
BODY SIZE (NOM)
TPS2561A-Q1
SON (10)
3.00mm x 3.00mm
spacer
spacer
Typical Application as Power Switch of Dual Port Automotive USB Charge Port Solution
USB
Connector1
5VOUT
100k 100k
0.1F
TPS2561A-Q1
Control Signal
Control Signal
DC to DC
Controller or converter
(LM25117-Q1,
TPS40170-Q1)
VBUS
DD+
OUT1
OUT2
IN
IN
FAULT2
ILIM
FAULT1
EN1
EN2 PowerPad GND
GND
RILIM
CUSB
USB
Connector2
COUT
VIN
DM1
VBUS
DP1
DD+
TPS2513A-Q1
DM2
GND
GND
DP2
CUSB
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
TPS2561A-Q1
SLVSCC6A – MARCH 2014 – REVISED JUNE 2014
www.ti.com
Table of Contents
1
2
3
4
5
6
7
8
9
Features ..................................................................
Applications ...........................................................
Description .............................................................
Revision History.....................................................
Device Comparison Table.....................................
Pin Functions and Configurations .......................
Specifications.........................................................
1
1
1
2
3
3
4
7.1
7.2
7.3
7.4
7.5
7.6
4
4
4
4
5
6
Absolute Maximum Ratings ......................................
Handling Ratings.......................................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
Electrical Characteristics...........................................
Typical Characteristics ..............................................
Parameter Measurement Information .................. 7
Detailed Description .............................................. 9
9.1 Overview ................................................................... 9
9.2 Functional Block Diagram ......................................... 9
9.3 Feature Description................................................... 9
9.4 Device Functional Mode ......................................... 10
10 Application and Implementation........................ 11
10.1 Application Information.......................................... 11
10.2 Typical Application ................................................ 11
11 Power Supply Requirements ............................. 17
12 Layout................................................................... 18
12.1 Layout Guidelines ................................................. 18
12.2 Layout Example .................................................... 18
13 Device and Documentation Support ................. 19
13.1 Trademarks ........................................................... 19
13.2 Electrostatic Discharge Caution ............................ 19
13.3 Glossary ................................................................ 19
14 Mechanical, Packaging, and Orderable
Information ........................................................... 19
4 Revision History
Changes from Original (March 2014) to Revision A
Page
•
Changed Feature From: Accurate 2.1A Min / 2.5A Max Setting (Including Resistor) To: Accurate 2.1A Min / 2.5A
Max Setting............................................................................................................................................................................. 1
•
Changed IOS, Current-limit. to include additional RILIM values. .............................................................................................. 5
•
Changed Equation 1 ............................................................................................................................................................ 11
•
Changed the Designing Above a Minimum Current Limit section........................................................................................ 12
•
Changed the Designing Below a Maximum Current Limit section ....................................................................................... 13
2
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SLVSCC6A – MARCH 2014 – REVISED JUNE 2014
5 Device Comparison Table
DEVICE
MAXIMUM OPERATING
CURRENT (A)
OUTPUTS
ENABLES
TYPICAL RDS(on) (mΩ)
PACKAGE
TPS2556-Q1
5
1
Active-low
22
SON-8 (DRB)
TPS2557-Q1
5
1
Active-high
22
SON-8 (DRB)
TPS2561A-Q1
2.5
2
Active-high
44
SON-10 (DRC)
6 Pin Functions and Configurations
DRC PACKAGE
(TOP VIEW)
GND
IN
IN
EN1
EN2
1
2
3
4
5
PAD
10
9
8
7
6
FAULT1
OUT1
OUT2
ILIM
FAULT2
Pin Functions
PIN
NAME
NUMBER
I/O
DESCRIPTION
EN1
4
I
Enable input, logic high turns on channel one power switch
EN2
5
I
Enable input, logic high turns on channel two power switch
GND
1
Ground connection; connect externally to PowerPAD
IN
2, 3
I
Input voltage; connect a 0.1 μF or greater ceramic capacitor from IN to GND
as close to the IC as possible.
FAULT1
10
O
Active-low open-drain output, asserted during overcurrent or overtemperature
condition on channel one.
FAULT2
6
O
Active-low open-drain output, asserted during overcurrent or overtemperature
condition on channel two
OUT1
9
O
Power-switch output for channel one
OUT2
8
O
Power-switch output for channel two
ILIM
7
O
External resistor used to set current-limit threshold; recommended 20 kΩ ≤
RILIM ≤ 187 kΩ.
PowerPAD™
PAD
Internally connected to GND; used to heat-sink the part to the circuit board
traces. Connect PowerPAD to GND pin externally.
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7 Specifications
7.1 Absolute Maximum Ratings
over operating free-air temperature range unless otherwise noted (1)
(2)
Voltage range on IN, OUTx, ENx, ILIM, FAULTx
Voltage range from IN to OUTx
Continuous output current
MIN
MAX
UNIT
–0.3
7
V
–7
7
V
Internally Limited
Continuous FAULTx sink current
25
ILIM source current
TJ
(1)
(2)
mA
Internally Limited
Maximum junction temperature
mA
Internally
Limited
–40
°C
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.
Voltages are referenced to GND unless otherwise noted.
7.2 Handling Ratings
TSTG
VESD
Storage temperature range
(1)
MIN
MAX
UNIT
-65
150
°C
kV
Human Body Model (HBM)
AEC-Q100 Classification Level H2
2
Charged Device Model (CDM)
AEC-Q100 Classification Level C5
750
V
8/15 (2)
kV
System level (contact/air)
(1)
(2)
Electrostatic discharge (ESD) to measure device sensitivity and immunity to damage caused by assembly line electrostatic discharges in
to the device.
Surges per EN61000-4-2, 1999 applied between USB connection for VBUS and GND of the TPS2560EVM (HPA424, replacing TPS2560
with TPS2561A-Q1) evaluation module (documentation available on the Web.) These were the test level, no the failure threshold.
7.3 Recommended Operating Conditions
MIN
MAX
UNIT
2.5
6.5
V
0
6.5
V
VIN
Input voltage, IN
VENx
Enable voltage
VIH
High-level input voltage on ENx
VIL
Low-level input voltage on ENx
IOUTx
Continuous output current per channel, OUTx
0
2.5
A
Continuous FAULTx sink current
0
10
mA
–40
125
°C
20
187
kΩ
TJ
Operating junction temperature
RILIM
Recommended resistor limit range
1.1
0.66
V
7.4 Thermal Information (1)
THERMAL METRIC
TPS2561A-Q1
DRC (10 TERMINALS)
θJA
Junction-to-ambient thermal resistance
38.1
θJCtop
Junction-to-case (top) thermal resistance
40.5
θJB
Junction-to-board thermal resistance
13.6
ψJT
Junction-to-top characterization parameter
0.6
ψJB
Junction-to-board characterization parameter
13.7
θJCbot
Junction-to-case (bottom) thermal resistance
3.4
(1)
4
UNIT
°C/W
For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.
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7.5 Electrical Characteristics
over recommended operating conditions, VENx = VIN (unless otherwise noted)
TEST CONDITIONS (1)
PARAMETER
MIN
TYP
MAX
44
50
UNIT
POWER SWITCH
rDS(on)
Static drain-source on-state
resistance per channel, IN to OUTx
tr
Rise time, output
tf
Fall time, output
TJ = 25°C
–40°C ≤TJ ≤125 °C
70
VIN = 6.5 V
1.5
3
VIN = 2.5 V
0.5
2
3
0.5
0.8
1.0
0.3
0.6
0.8
VIN = 6.5 V
CLx = 1 μF, RLx = 100 Ω,
(see Figure 9)
VIN = 2.5 V
mΩ
4
ms
ENABLE INPUT EN
Enable pin turn on/off threshold
0.66
IEN
Input current
ton
Turnon time
toff
Turnoff time
1.1
55 (2)
Hysteresis
VENx = 0 V or 6.5 V
–0.5
CLx = 1 μF, RLx = 100 Ω, (see Figure 9)
V
mV
0.5
μA
9
ms
6
ms
CURRENT LIMIT
IOS
Current-limit (see Figure 11)
OUTx connected to GND
OUT1 and OUT2 connected to GND
tIOS
Response time to short circuit
RILIM = 20 kΩ
2560
2750
2980
RILIM = 24.3 kΩ
2100
2250
2500
RILIM = 61.9 kΩ
800
900
1005
RILIM = 100 kΩ
470
560
645
RILIM = 47.5 kΩ
2100
2300
2500
3.5 (2)
VIN = 5 V (see Figure 10)
mA
μs
SUPPLY CURRENT
IIN(off)
Supply current, low-level output
0.1
2.0
μA
RILIM = 20 kΩ
100
125
μA
RILIM = 100 kΩ
85
110
μA
0.01
1.0
μA
2.45
VIN = 6.5 V, No load on OUTx, VENx = 0 V
IIN(on)
Supply current, high-level output
VIN = 6.5 V, No load on OUT
IREV
Reverse leakage current
VOUTx = 6.5 V, VIN = 0 V
TJ = 25°C
UNDERVOLTAGE LOCKOUT
VUVLO
Low-level input voltage, IN
VIN rising
2.35
Hysteresis, IN
TJ = 25°C
35 (2)
V
mV
FAULTx FLAG
VOL
Output low voltage, FAULTx
I FAULTx = 1 mA
180
Off-state leakage
V FAULTx = 6.5 V
FAULTx deglitch
FAULTx assertion or de-assertion due to overcurrent condition
6
9
mV
1
μA
13
ms
THERMAL SHUTDOWN
Thermal shutdown threshold, OTSD2
155
Thermal shutdown threshold in current-limit, OTSD
135
(2)
°C
20 (2)
Hysteresis
(1)
°C
°C
Pulse-testing techniques maintain junction temperature close to ambient temperature; thermal effects must be taken into account
separately.
These parameters are provided for reference only, and do not constitute part of TI's published specifications for purposes of TI's product
warranty.
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7.6 Typical Characteristics
700
2.335
IIN - Supply Current, Output Disabled - nA
UVLO - Undervoltage Lockout - V
2.33
2.325
UVLO Rising
2.32
2.315
2.31
2.305
UVLO Falling
2.3
2.295
2.29
-50
0
50
TJ - Junction Temperature - °C
100
400
VIN = 6.5 V
300
200
VIN = 2.5 V
100
0
50
TJ - Junction Temperature - °C
100
150
120
VIN = 6.5 V
VIN = 5 V
TJ = 125°C
IIN Supply Current vs. VIN Enabled - μA
100
80
VIN = 3.3 V
VIN = 2.5 V
60
40
20
0
-50
0
50
TJ - Junction Temperature - °C
100
110
100
90
80
TJ = 25°C
TJ = -40°C
70
60
150
2
RLIM = 20 kΩ
3
4
5
Input Voltage - V
6
7
RLIM = 20 kΩ
Figure 3. IIN – Supply Current, Output Enabled – µA
Figure 4. IIN – Supply Current, Output Enabled – µA
0.6
60
0.5
IDS - Static Drain-Source Current - A
70
50
40
30
20
TA = -40°C
0.4
TA = 25°C
TA = 125°C
0.3
0.2
0.1
10
0
-50
0
Figure 2. IIN – Supply Current, Output Disabled – nA
Figure 1. UVLO – Undervoltage Lockout – V
IIN - Supply Current, Output Enabled - mA
500
-100
-50
150
120
rDS(on) - Static Drain-Source On-State Resistance - mW
600
0
0
50
TJ - Junction Temperature - °C
100
150
0
50
100
VIN - VOUT - mV/div
150
200
RLIM = 100 kΩ
Figure 5. MOSFET rDS(on) Vs. Junction Temperature
6
Figure 6. Switch Current Vs. Drain-Source Voltage Across
Switch
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Typical Characteristics (continued)
1.0
3.0
2.5
0.8
0.7
IDS - Static Drain-Source Current - A
IDS - Static Drain-Source Current - A
0.9
TA = -40°C
0.6
TA = 25°C
0.5
TA = 125°C
0.4
0.3
0.2
TJ = -40°C
2.0
TJ = 25°C
1.5
1.0
TJ = 125°C
0.5
0.1
0
0
0
20
40
60
80
100
VIN - VOUT - mV/div
120
140
0
160
RLIM = 61.9 kΩ
50
100
VIN-VOUT - mV
150
200
RLIM = 20 kΩ
Figure 7. Switch Current Vs. Drain-Source Voltage Across
Switch
Figure 8. Switch Current vs. Drain-Source Voltage Across
Switch
8 Parameter Measurement Information
OUTx
tr
CLx
RLx
tf
VOUTx
90%
90%
10%
10%
TEST CIRCUIT
VENx
50%
50%
VENx
ton
toff
50%
50%
toff
ton
90%
90%
VOUTx
VOUTx
10%
10%
VOLTAGE WAVEFORMS
Figure 9. Test Circuit and Voltage Waveforms
IOS
IOUTx
tIOS
Figure 10. Response Time to Short Circuit Waveform
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Parameter Measurement Information (continued)
Decreasing
Load Resistance
VOUTx
Decreasing
Load Resistance
IOUTx
IOS
Figure 11. Output Voltage vs. Current-Limit Threshold
8
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9 Detailed Description
9.1 Overview
The TPS2561A-Q1 is a dual-channel, current-limited power-distribution switch using N-channel MOSFETs for
automotive applications where short circuits or heavy capacitive loads will be encountered. This device allows
the user to program the current-limit threshold between 250 mA and 2.8 A (typ) per channel via an external
resistor. This device incorporates an internal charge pump and gate drive circuitry necessary to drive the Nchannel MOSFETs. The charge pump supplies power to the driver circuit for each channel 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 2.5 V and requires little supply current. The driver controls the gate voltage of the power
switch. The driver incorporates circuitry that controls the rise and fall times of the output voltage to limit large
current and voltage surges and provides built-in soft-start functionality. Each channel of the TPS2561A-Q1 limits
the output current to the programmed current-limit threshold IOS during an overcurrent or short-circuit event by
reducing the charge pump voltage driving the N-channel MOSFET and operating it in the linear range of
operation. The result of limiting the output current to IOS reduces the output voltage at OUTx because the Nchannel MOSFET is no longer fully enhanced.
9.2 Functional Block Diagram
Current
Sense
CS
IN
OUT1
FAULT1
9-ms Deglitch
Thermal
Sense
Charge
Pump
EN1
EN2
Current
Limit
Driver
UVLO
ILIM
FAULT2
Thermal
Sense
9-ms Deglitch
GND
CS
OUT2
Current
Sense
9.3 Feature Description
9.3.1 Overcurrent Conditions
The TPS2561A-Q1 responds to overcurrent conditions by limiting the output current per channel to IOS. When an
overcurrent condition is detected, the device maintains a constant output current and reduces the output voltage
accordingly. Two possible overload conditions can occur.
The first condition is when a short circuit or partial short circuit is present when the device is powered-up or
enabled. The output voltage is held near zero potential with respect to ground and the TPS2561A-Q1 ramps the
output current to IOS. The TPS2561A-Q1 devices will limit the current to IOS until the overload condition is
removed or the device begins to thermal cycle.
The second condition is when a short circuit, partial short circuit, or transient overload occurs while the device is
enabled and powered on. The device responds to the overcurrent condition within time tIOS (see Figure 10). The
current-sense amplifier is overdriven during this time and momentarily disables the internal current-limit
MOSFET. The current-sense amplifier recovers and ramps the output current to IOS. Similar to the previous case,
the TPS2561A-Q1 will limit the current to IOS until the overload condition is removed or the device begins to
thermal cycle.
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Feature Description (continued)
The TPS2561A-Q1 thermal cycles if an overload condition is present long enough to activate thermal limiting in
any of the above cases. The device turns off when the junction temperature exceeds 135°C (min) while in current
limit. The device remains off until the junction temperature cools 20°C (typ) and then restarts. The TPS2561A-Q1
cycles on/off until the overload is removed (see Figure 20) .
9.3.2
FAULTx Response
The FAULTx open-drain outputs are asserted (active low) on an individual channel during an overcurrent or
overtemperature condition. The TPS2561A-Q1 asserts the FAULTx signal until the fault condition is removed and
the device resumes normal operation on that channel. The TPS2561A-Q1 is designed to eliminate false FAULTx
reporting by using an internal delay "deglitch" circuit (9-ms typ) for overcurrent conditions without the need for
external circuitry. This ensures that FAULTx is not accidentally asserted due to normal operation such as starting
into a heavy capacitive load. The deglitch circuitry delays entering and leaving current-limited induced fault
conditions. The FAULTx signal is not deglitched when the MOSFET is disabled due to an overtemperature
condition but is deglitched after the device has cooled and begins to turn on. This unidrectional deglitch prevents
FAULTx oscillation during an overtemperature event.
9.3.3 Thermal Sense
The TPS2561A-Q1 self protects by using two independent thermal sensing circuits that monitor the operating
temperature of the power switch and disable operation if the temperature exceeds recommended operating
conditions. Each channel of the TPS2561A-Q1 operates in constant-current mode during an overcurrent
conditions, which increases the voltage drop across the power switch. The power dissipation in the package is
proportional to the voltage drop across the power switch, which increases the junction temperature during an
overcurrent condition. The first thermal sensor (OTSD) turns off the individual power switch channel when the die
temperature exceeds 135°C (min) and the channel is in current limit. Hysteresis is built into the thermal sensor,
and the switch turns on after the device has cooled approximately 20°C.
The TPS2561A-Q1 also has a second ambient thermal sensor (OTSD2). The ambient thermal sensor turns off
both power switch channels when the die temperature exceeds 155°C (min) regardless of whether the power
switch channels are in current limit and will turn on the power switches after the device has cooled approximately
20°C. The TPS2561A-Q1 continues to cycle off and on until the fault is removed.
9.4 Device Functional Mode
9.4.1 Undervoltage Lockout (UVLO)
The undervoltage lockout (UVLO) circuit disables the power switch until the input voltage reaches the UVLO turnon threshold. Built-in hysteresis prevents unwanted on/off cycling due to input voltage droop during turn on.
9.4.2 Enable (ENx)
The logic enables control the power switches and device supply current. The supply current is reduced to less
than 2-μA when a logic low is present on ENx. A logic high input on ENx enables the driver, control circuits, and
power switches. The enable inputs are compatible with both TTL and CMOS logic levels.
10
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10 Application and Implementation
10.1 Application Information
The device is current-limited, power-distribution switch. It would limit the output current to IOS when short circuits
or heavy capacitive loads are encountered.
10.2 Typical Application
10.2.1 Design Current Limit
VIN = 5V
0.1 uF
2x RFAULT
100 kΩ
TPS2561A-Q1
IN
OUT1
IN
OUT2
ILIM
FAULT 1
FAULT 2 GND
EN1
EN2
Power Pad
Faultx Signals
Control Signals
VOUT1
VOUT2
24.9kΩ
2x 150 µF
Figure 12. Typical Characteristics Reference Schematic
10.2.1.1 Design Requirements
For this design example, use the following as the input parameters.
Table 1. Design Parameters
DESIGN PARAMTER
EXAMPLE VALUE
Input voltage
5V
Minimum current limit
2A
Maximum current limit
1A
10.2.1.2 Detailed Design Procedure
10.2.1.2.1 Determine Design Parameters
Beginning the design process requires deciding on a few parameters. The designer must know the following:
• Input voltage
• Minimum current limit
• Maximum current limit
10.2.1.2.2 Programming the Current-Limit Threshold
The overcurrent threshold is user programmable via an external resistor, RILIM. RILIM sets the current-limit
threshold for both channels. The TPS2561A-Q1 use an internal regulation loop to provide a regulated voltage on
the ILIM pin. The current-limit threshold is proportional to the current sourced out of ILIM. The recommended 1%
resistor range for RILIM is 20 kΩ ≤ RILIM ≤ 187 kΩ to ensure stability of the internal regulation loop. Many
applications require that the minimum current limit is above a certain current level or that the maximum current
limit is below a certain current level, so it is important to consider the tolerance of the overcurrent threshold when
selecting a value for RILIM. The following equations calculates the resulting overcurrent threshold for a given
external resistor value (RILIM). The traces routing the RILIM resistor to the TPS2561A-Q1 should be as short as
possible to reduce parasitic effects on the current-limit accuracy.
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IOSmax (mA) =
IOSnom (mA) =
IOSmin (mA) =
49497V
www.ti.com
- 37
R(ILIM)0.933kW
53098V
R(ILIM)0.989kW
50576V
R(ILIM)0.987kW
- 64
(1)
3000
2750
Current-Limit Threshold (mA)
2500
2250
2000
1750
1500
1250
1000
IOS(max)
IOS(typ)
750
500
IOS(min)
250
0
20
30
40
50
60
70
80
90
100
110
120
130
140
150
RILIM – Current Limit Resistor – kΩ
Figure 13. Current-Limit Threshold vs. RILIM
10.2.1.2.3 Designing Above a Minimum Current Limit
Some applications require that current limiting cannot occur below a certain threshold. For this example, assume
that 2 A must be delivered to the load so that the minimum desired current-limit threshold is 2000 mA. Use the
IOS equations and Figure 13 to select RILIM.
IOSmin (mA) = 2000 mA
IOSmin (mA) =
50576V
R(ILIM)0.987kW
- 64
1
1
æ 50576 ö 0.987 æ 50576 ö 0.987
=ç
= 25.56kW
R(ILIM) (kW) = ç
÷
÷
ç IOS(min) + 64 ÷
è 2000 + 64 ø
è
ø
(2)
Select the closest 1% resistor less than the calculated value: RILIM = 25.5 kΩ. This sets the minimum current-limit
threshold at 2005 mA .
50576
50576
IOSmin (mA) =
- 64 =
- 64 = 2005 mA
0.987
R(ILIM)
kW
(25.5)0.987
(3)
Use the IOS equations, Figure 13, and the previously calculated value for RILIM to calculate the maximum resulting
current-limit threshold at 2374 mA.
49497
49497
IOSmax (mA) =
- 37 =
- 37 = 2374 mA
0.933
R(ILIM)
(25.5)0.933
(4)
12
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10.2.1.2.4 Designing Below a Maximum Current Limit
Some applications require that current limiting must occur below a certain threshold. For this example, assume
that 1 A must be delivered to the load so that the minimum desired current-limit threshold is 1000 mA. Use the
IOS equations and Figure 13 to select RILIM.
IOSmax (mA) = 1000 mA
IOSmax (mA) =
49497
R(ILIM)0.933kW
- 37
1
æ 49497
R(ILIM) (kW) = ç
ç
è IOS(max)
1
ö 0.933 æ 49497 ö 0.933
=ç
= 63kW
÷
÷
÷
è 1000 + 37 ø
ø
(5)
Select the closest 1% resistor greater than the calculated value: RILIM = 63.4 kΩ. This sets the maximum currentlimit threshold at 994 A.
49497
49497
IOSmax (mA) =
- 37 =
- 37 = 994 mA
0.933
R(ILIM)
kW
(63.4)0.933
(6)
Use the IOS equations, Figure 13, and the previously calculated value for RILIM to calculate the minimum resulting
current-limit threshold at 778 mA.
50576
50576
IOSmin (mA) =
- 64 =
- 64 = 778 mA
0.987
R(ILIM)
(63.4)0.987
(7)
10.2.1.2.5 Accounting for Resistor Tolerance
The previous sections described the selection of RILIM given certain application requirements and the importance
of understanding the current-limit threshold tolerance. The analysis focused only on the TPS2561A-Q1
performance and assumed an exact resistor value. However, resistors sold in quantity are not exact and are
bounded by an upper and lower tolerance centered around a nominal resistance. The additional RILIM resistance
tolerance directly affects the current-limit threshold accuracy at a system level. The following table shows a
process that accounts for worst-case resistor tolerance assuming 1% resistor values. Step one follows the
selection process outlined in the application examples above. Step two determines the upper and lower
resistance bounds of the selected resistor. Step three uses the upper and lower resistor bounds in the IOS
equations to calculate the threshold limits. It is important to use tighter tolerance resistors, that is, 0.5% or 0.1%,
when precision current limiting is desired.
Table 2. Common RILIM Resistor Selections
Desired
Nominal
Current Limit
(mA)
Ideal Resistor
(kΩ)
Closest 1%
Resistor (kΩ)
Resistor Tolerance
Actual Limits
1% low (kΩ)
1% high (kΩ)
IOS MIN (mA)
IOS Nom (mA)
IOS MAX (mA)
300
187.5
187
185.1
188.9
223
301
342
550
101.6
102
101.0
103.0
457
548
631
800
69.5
69.8
69.1
70.5
694
797
914
1050
52.8
52.3
51.8
52.8
944
1060
1208
1300
42.6
42.2
41.8
42.6
1182
1311
1484
1550
35.6
35.7
35.3
36.1
1406
1547
1741
1800
30.6
30.9
30.6
31.2
1631
1784
1998
2050
26.9
26.7
26.4
27.0
1894
2062
2295
2300
23.9
23.7
23.5
23.9
2138
2320
2569
2550
21.5
21.5
21.3
21.7
2360
2554
2817
2800
19.6
19.6
19.4
19.8
2592
2799
3075
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10.2.1.2.6 Power Dissipation and Junction Temperature
The low on-resistance of the N-channel MOSFET allows small surface-mount packages to pass large currents. It
is good design practice to estimate power dissipation and junction temperature. The below analysis gives an
approximation for calculating junction temperature based on the power dissipation in the package. However, it is
important to note that thermal analysis is strongly dependent on additional system level factors. Such factors
include air flow, board layout, copper thickness and surface area, and proximity to other devices dissipating
power. Good thermal design practice must include all system level factors in addition to individual component
analysis.
Begin by determining the rDS(on) of the N-channel MOSFET relative to the input voltage and operating
temperature. As an initial estimate, use the highest operating ambient temperature of interest and read RDS(on)
from the typical characteristics graph. Using this value, the power dissipation can be calculated by:
PD = (RDS(on) × IOUT1 2) +(RDS(on) × IOUT2 2)
Where:
PD = Total power dissipation (W)
rDS(on) = Power switch on-resistance of one channel (Ω)
IOUTx = Maximum current-limit threshold set by RILIM(A)
This step calculates the total power dissipation of the N-channel MOSFET.
Finally, calculate the junction temperature:
TJ = PD × θJA + TA
Where:
TA = Ambient temperature (°C)
θJA = Thermal resistance (°C/W)
PD = Total power dissipation (W)
Compare the calculated junction temperature with the initial estimate. If they are not within a few degrees, repeat
the calculation using the "refined" RDS(on) from the previous calculation as the new estimate. Two or three
iterations are generally sufficient to achieve the desired result. The final junction temperature is highly dependent
on thermal resistance θJA, and thermal resistance is highly dependent on the individual package and board
layout. The Thermal Characteristics Table provides example thermal resistances for specific packages and board
layouts.
14
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10.2.1.2.7 Auto-Retry Functionality
Some applications require that an overcurrent condition disables the part momentarily during a fault condition
and re-enables after a pre-set time. This auto-retry functionality can be implemented with an external resistor and
capacitor. During a fault condition, FAULTx pulls ENx low disabling the part. The part is disabled when ENx is
pulled below the turn-off threshold, and FAULTx goes high impedance allowing CRETRY to begin charging. The
part re-enables when the voltage on ENx reaches the turn-on threshold, and the auto-retry time is determined by
the resistor, capacitor time constant. The part will continue to cycle in this manner until the fault condition is
removed.
Input
0.1 μF
RFAULT
2x 100 kΩ
TPS2561A-Q1
OUT1
IN
OUT2
2x CLOAD
ILIM
FAULT1
GND
EN1
FAULT2
EN2
CRETRY
2x 0.22 µF
VOUT1
VOUT2
RILIM
20 kΩ
Power Pad
Figure 14. Auto-Retry Functionality
Some applications require auto-retry functionality and the ability to enable/disable with an external logic signal.
The figure below shows how an external logic signal can drive EN through RFAULT and maintain auto-retry
functionality. The resistor/capacitor time constant determines the auto-retry time-out period.
Input
External Logic
Signal & Drivers
RFAULT
2x 100 kΩ
CRETRY
2x 0.22 µF
0.1 μF
TPS2561A-Q1
OUT1
IN
OUT2
VOUT1
VOUT2
2x CLOAD
ILIM
FAULT1
GND
EN1
FAULT2
EN2
RILIM
20 kΩ
Power Pad
Figure 15. Auto-Retry Functionality With External EN Signal
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10.2.1.2.8 Two-Level Current-Limit Circuit
Some applications require different current-limit thresholds depending on external system conditions. Figure 16
shows an implementation for an externally controlled, two-level current-limit circuit. The current-limit threshold is
set by the total resistance from ILIM to GND (see previously discussed Programming the Current-Limit Threshold
section). A logic-level input enables/disables MOSFET Q1 and changes the current-limit threshold by modifying
the total resistance from ILIM to GND. Additional MOSFET/resistor combinations can be used in parallel to
Q1/R2 to increase the number of additional current-limit levels.
NOTE
ILIM should never be driven directly with an external signal.
2.5V – 6.5V
2x RFAULT
100 kΩ
Fault Signal
Fault Signal
Control Signal
Control Signal
0.1 μF
TPS2561A-Q1
IN
OUT1
IN
OUT2
FAULT1
FAULT2 ILIM
EN1
GND
EN2
Power Pad
VOUT1
VOUT2
2x CLOAD
R1
187 kΩ
R2
22.1 kΩ
Q1
Current Limit
Control Signal
Figure 16. Two-Level Current-Limit Circuit
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10.2.2 Application Curves
VOUT1
5 V/div
VOUT1
5 V/div
VOUT2
5 V/div
VOUT2
5 V/div
VEN1 = VEN2
VEN1 = VEN2
5 V/div
5 V/div
IIN
2 A/div
IIN
2 A/div
t - Time - 2 ms/div
t - Time - 2 ms/div
Figure 17. Turn-on Delay and Rise Time
VOUT1
5 V/div
Figure 18. Turn-off Delay and Fall Time
VOUT1
5 V/div
VOUT2
5 V/div
VOUT2
5 V/div
FAULT2_bar
5 V/div
FAULT2_bar
5 V/div
IIN
2 A/div
IIN
2 A/div
t - Time - 20 ms/div
t - Time - 20 ms/div
Figure 19. Full-Load to Short-Circuit Transient Response
Figure 20. Short-Circuit to Full-Load Recovery Response
11 Power Supply Requirements
The device is designed to operate from an input voltage supply range of 2.5 V to 6.5 V. The current capability of
upper power should exceed the max current limit of the power switch.
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12 Layout
12.1 Layout Guidelines
For all applications, a 0.1-µF or greater ceramic bypass capacitor between IN and GND is recommended as
close to the device as possible for local noise decoupling. This precaution reduces ringing on the input due to
power-supply transients. Additional input capacitance may be needed on the input to reduce voltage overshoot
form exceeding the absolute-maximum voltage of the device during heavy transient conditions.
• Output capacitance is not required, but placing a high-value electrolytic capacitor on the output pin is
recommended when large transient currents are expected on the output.
• The traces routing the RILIM resistor to the device should be as short as possible to reduce parasitic effects on
the current limit accuracy.
• The PowerPAD™ should be directly connected to PCB ground plane using wide and short copper trace.
12.2 Layout Example
VIA to Power Ground Plane
Power Ground
FAULT1
1
10
OUT1
High Frequency
Bypass Capacitor
2
9
3
8
4
7 ILIM
5
6
IN
OUT2
FAULT2
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13 Device and Documentation Support
13.1 Trademarks
PowerPAD is a trademark of Texas Instruments.
13.2 Electrostatic Discharge Caution
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
13.3 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms and definitions.
14 Mechanical, Packaging, and Orderable Information
The following pages include mechanical packaging and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and revision of
this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
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PACKAGE OPTION ADDENDUM
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10-Dec-2020
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
(4/5)
(6)
TPS2561AQDRCRQ1
ACTIVE
VSON
DRC
10
3000
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 125
2561AQ
TPS2561AQDRCTQ1
ACTIVE
VSON
DRC
10
250
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 125
2561AQ
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
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