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TPS2505
SPAS093C – DECEMBER 2009 – REVISED SEPTEMBER 2015
TPS2505 Integrated Dual USB Switches, Boost Converter and LDO
1 Features
3 Description
•
The TPS2505 device provides an integrated solution
to meet USB 5-V power requirements from a 1.8-V to
5.25-V input supply. The features include a 5.1-V,
1100-mA boost converter, a 200-mA, 3.3-V LDO
linear regulator and dual USB 2.0 compliant power
outputs with independent output switch enable,
current limit, and overcurrent fault reporting.
1
•
•
•
•
•
•
•
•
•
Integrated Synchronous Boost Converter, LDO,
and Dual USB Current-Limited Switches
1.8-V to 5.25-V Input Voltage
(2.2-V Minimum Start-Up Voltage)
Adjustable Independent USB Current Limit
– 100 mA to 1100 mA
Auxiliary 5.1-V Output
3.3-V Linear Regulator Output
Inrush Current < 100 mA
Minimal External Components Required
Deglitched Independent Fault Reporting
Small 5-mm × 5-mm QFN-20 Package
Industrial Temperature Range
The 1.8-V to 5.25-V input can be supplied by sources
including DC-DC regulated supplies (for example, 3.3
V), or batteries such as single cell Li+, two-cell or
three-cell NiCd, NiMH or alkaline.
The output trip current for the dual USB switches can
be programmed through external resistors from as
low as 100 mA to as high as 1100 mA.
An auxiliary 5.1-V output is provided, where the total
current supplied by the USB outputs and the auxiliary
by cannot exceed 1100 mA.
2 Applications
•
•
•
•
Portable Applications Using Single Li+ Cell
Bus Powered USB Hosts
USB Hosts Without Native 5-V Supplies
Computer Peripherals
Device Information(1)
PART NUMBER
TPS2505
PACKAGE
BODY SIZE (NOM)
VQFN (20)
5.00 mm × 5.00 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
Typical Application
2.2µH
Power
Supply
1.8V – 5.25V
SW
IN
10µF
EN
RESET
3.3V Power
LDOOUT
1µF
EN_LDO
LDOIN
HUB
CONTROLLER
RFAULT 1
5V USB Power
USB1
5V Output
AUX
120µF
22µF
TPS2505
RFAULT 2
5V USB Power
USB2
FAULT 1
120µF
FAULT 2
ILIM1
RLIM1
ENUSB1
ILIM2
ENUSB2
GND
PAD
PGND
RLIM2
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.
TPS2505
SPAS093C – DECEMBER 2009 – REVISED SEPTEMBER 2015
www.ti.com
Table of Contents
1
2
3
4
5
6
Features ..................................................................
Applications ...........................................................
Description .............................................................
Revision History.....................................................
Pin Configuration and Functions .........................
Specifications.........................................................
1
1
1
2
3
4
6.1
6.2
6.3
6.4
6.5
4
4
4
4
Absolute Maximum Ratings ......................................
ESD Ratings..............................................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
Electrical Characteristics (Shared Boost, LDO and
USB)...........................................................................
6.6 Electrical Characteristics (Boost Only)......................
6.7 Electrical Characteristics (USB1/2 Only) ..................
6.8 Electrical Characteristics (LDO and Reset Only)......
6.9 Recommended External Components ......................
6.10 Dissipation Ratings .................................................
6.11 Typical Characteristics ............................................
7
5
5
6
7
7
7
8
Parameter Measurement Information .................. 9
8
Detailed Description ............................................ 10
8.1
8.2
8.3
8.4
9
Overview .................................................................
Functional Block Diagram .......................................
Feature Description.................................................
Device Functional Modes........................................
10
10
11
18
Application and Implementation ........................ 19
9.1 Application Information............................................ 19
9.2 Typical Application ................................................. 19
10 Power Supply Recommendations ..................... 23
11 Layout................................................................... 24
11.1 Layout Guidelines ................................................. 24
11.2 Layout Example .................................................... 24
12 Device and Documentation Support ................. 25
12.1
12.2
12.3
12.4
Community Resources..........................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
25
25
25
25
13 Mechanical, Packaging, and Orderable
Information ........................................................... 25
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision B (June 2010) to Revision C
•
2
Page
Added Pin Configuration and Functions section, ESD Ratings table, Feature Description section, Device Functional
Modes, Application and Implementation section, Power Supply Recommendations section, Layout section, Device
and Documentation Support section, and Mechanical, Packaging, and Orderable Information section .............................. 1
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SPAS093C – DECEMBER 2009 – REVISED SEPTEMBER 2015
5 Pin Configuration and Functions
USB1
USB1
17
16
SW
20 19 18
SW
AUX
RGW Package
20-Pin VQFN With Exposed Thermal Pad
Top View
PGND 1
15 USB2
6
7
8
9
10
LDOOUT
11 LDOIN
RESET
12 ENLDO
ILIM1 5
ENUSB1
13 FAULT2
GND 4
ILIM2
14 ENUSB2
EN 3
FAULT1
IN 2
Pin Functions
PIN
NAME
NO.
TYPE (1)
DESCRIPTION
18
O
Fixed 5.1-V boost converter output. Connect a low-ESR ceramic capacitor from AUX to
PGND.
EN
3
I
Enable input for boost converter. Tie to IN to enable.
ENLDO
12
I
Enable input for the LDO. Tie to AUX to enable.
ENUSB1
8
I
Enable input for the USB1 switch. Tie to IN or AUX to enable.
ENUSB2
14
I
Enable input for the USB2 switch. Tie to IN or AUX to enable.
FAULT1
7
O
Active low USB1 fault indicator (open drain).
FAULT2
13
O
Active low USB2 fault indicator (open drain).
GND
4
P
Control / logic ground. Must be tied to PGND close to the IC externally.
ILIM1
5
I
Program the nominal USB1 switch current-limit threshold with a resistor to GND.
ILIM2
6
I
Program the nominal USB2 switch current-limit threshold with a resistor to GND.
IN
2
I
Input supply voltage for boost converter.
LDOIN
11
I
Input supply voltage for LDO. Connect to AUX.
LDOOUT
10
O
Fixed 3.3-V LDO output. Connect a low-ESR ceramic capacitor from LDOOUT to GND.
PGND
1
P
Source connection for the internal low-side boost converter power switch. Connect to GND
with a low impedance connection to the input and output capacitors.
RESET
9
O
Active low LDO output good indicator (open drain).
SW
19
P
Boost and rectifying switch input. This node is switched between PGND and AUX. Connect
the boost inductor from IN to SW.
SW
20
P
Boost and rectifying switch input. This node is switched between PGND and AUX. Connect
the boost inductor from IN to SW.
USB1
16
O
Output of the USB1 power switch. Connect to the USB1 port.
USB1
17
O
Output of the USB1 power switch. Connect to the USB1 port.
USB2
15
O
Output of the USB2 power switch. Connect to the USB2 port.
Thermal Pad
—
—
Internally connected to PGND. Must be soldered to board ground for thermal dissipation.
AUX
(1)
I = Input; O = Output; P = Power
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SPAS093C – DECEMBER 2009 – REVISED SEPTEMBER 2015
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6 Specifications
6.1 Absolute Maximum Ratings
Over operating free-air temperature range (unless otherwise noted). (1) (2)
MIN
MAX
UNIT
–0.3
7
V
FAULT sink current
25
mA
ILIM source current
1
mA
Input voltage on SW, AUX, IN, USB, ENUSB, EN, FAULT, ILIM
Operating junction temperature, TJ
–40
125
°C
Storage temperature, Tstg
–65
150
°C
(1)
(2)
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 and PGND tied together.
6.2 ESD Ratings
VALUE
V(ESD)
(1)
(2)
Electrostatic discharge
Human body model (HBM), per ANSI/ESDA/JEDEC JS-001, all
pins (1)
±2000
Charged device model (CDM), per JEDEC specification JESD22C101, all pins (2)
±500
UNIT
V
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.
6.3 Recommended Operating Conditions
over operating free-air temperature range (unless otherwise noted)
MIN
MAX
UNIT
VIN
Supply voltage at IN
1.8
5.25
V
VSTART
Supply voltage at IN for start-up
2.2
Enable voltage at EN, ENUSB1, ENUSB2, ENLDO
V
0
5.25
V
TA
Operating free air temperature range
–40
85
°C
TJ
Operating junction temperature range
–40
125
°C
6.4 Thermal Information
TPS2505
THERMAL METRIC
(1)
RGW (VQFN)
UNIT
20 PINS
RθJA
Junction-to-ambient thermal resistance
RθJC(top)
Junction-to-case (top) thermal resistance
34.3
°C/W
30
°C/W
RθJB
ψJT
Junction-to-board thermal resistance
13.5
°C/W
Junction-to-top characterization parameter
0.4
°C/W
ψJB
Junction-to-board characterization parameter
13.5
°C/W
RθJC(bot)
Junction-to-case (bottom) thermal resistance
3.1
°C/W
(1)
4
For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application
report, SPRA953.
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6.5 Electrical Characteristics (Shared Boost, LDO and USB)
over recommended operating conditions (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
BIAS
Bias Current
Shutdown current
VIN
VIN = 3.3 V, VAUX = 5.2 V, VEN = VIN,
VENUSB1 = VAUX, IAUX = IUSB = 0 A
VAUX
VIN = 3.3 V, VEN = VENUSB = 0 V,
AUX and USB OPEN,
–40°C ≤ TJ ≤ 85°C
VIN
15
25
500
600
µA
5
µA
UVLO
VIN rising
Undervoltage lockout threshold on IN for boost
converter
2.08
VIN falling,
VAUX = 5.2 V
Threshold
VIN falling,
VAUX = OPEN
Threshold
Hysteresis
VAUX falling
1.85
0.4
1.93
Hysteresis
V
2.05
0.15
VAUX rising
Undervoltage lockout threshold on AUX for USB
switches
2.20
1.69
Threshold
4.18
4.45
4.1
4.37
Hysteresis
V
0.09
THERMAL SHUTDOWN
Full thermal shutdown thereshold
150
Hysteresis
°C
10
USB only thermal shutdown
°C
130
Hysteresis
°C
10
°C
6.6 Electrical Characteristics (Boost Only)
over recommended operating conditions (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
4.75
5.1
5.25
V
APPLICATION SPECIFICATIONS
VAUX
VRIPPLE
AUX regulation voltage
AUX ripple voltage
Load regulation (1)
Line regulation
VREF
Includes ripple and line/load
regulation
USB1/2 enabled
CUSB1/2 = 100 µF
PFM, IO = 100 mA
USB1/2 enabled
CUSB1/2 = 100 µF
250
mV
PWM, IO = 1100 mA
USB1/2 enabled
CUSB1/2 = 100 µF
75
IO = 0 mA to 1100 mA (PWM
operation only)
50
IO = 1100 mA (PWM operation)
50
300 (2)
IO = 1100 mA, VIN = 3.6 V to 5.25 V
Internal reference voltage
1.35
mV
mV
V
OSCILLATOR
freq
VLFM
Switching frequency, normal mode
VIN < VLFM
850
1000
1150
kHz
Switching frequency, low-frequency
mode
VIN > VLFM
225
250
275
kHz
4.25
4.35
4.45
V
Low-frequency mode input voltage
threshold
Hysteresis
(1)
(2)
200
mV
Load regulation in No Frequency or Pass-Through is given by IR drop across SWP switch resistance..
Includes voltage drop when transitioning to No Frequency or Pass-Through Mode, where VAUX is no longer a closed loop regulated
voltage and drops to VNFM – ILOADRSWP. For No Frequency or Pass-Through, ΔVAUX/ ΔVIN = 1.
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Electrical Characteristics (Boost Only) (continued)
over recommended operating conditions (unless otherwise noted)
PARAMETER
No-frequency mode input voltage
threshold
(Boost SYNC MOSFET always on)
VNFM
TEST CONDITIONS
VIN rising
MIN
TYP
MAX
UNIT
4.9
5.05
5.17
V
Hysteresis
75
Maximum duty cycle
mV
85%
Minimum controllable on-time
85
ns
420
mA
PULSE FREQUENCY MODE (PFM)
IINDLOW
Demanded peak current to enter
PFM mode
Peak inductor current, falling
AUXLOW
AUX too low comparator threshold
Resume switching due to AUX,
falling
0.98 ×
VAUX
V
POWERSTAGE
Switch on resistance (SWN)
120
Peak switch current limit
(SWN MOSFET)
ISW
3
Switch ON-resistance (SWP)
Vsg = VMAX
Switch ON-resistance (SWP + USB)
VIN > VNFM
4.5
125
6
mΩ
A
125
mΩ
185
mΩ
0.1
A
START UP (3)
ISTART
Constant current
VEXIT
Constant current exit threshold
(VIN –VAUX)
tstartup
Boost startup time
700
VIN = 5.1 V, COUT = 150 µF
25
mV
40
ms
0.7
1
V
–0.5
0.5
µA
BOOST ENABLE (EN)
Enable threshold, boost converter
IEN
(3)
Input current
VEN = 0 V or 5.5 V
VAUX pin must be unloaded during start-up.
6.7 Electrical Characteristics (USB1/2 Only)
over recommended operating conditions (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
USB1, USB2
rDS(on)
USB switch resistance
80
mΩ
2
3
ms
2.5
3.5
ms
5.25
mV
tr
Rise time, output
VAUX = 5.1 V, CL = 100 µF,
RL = 10 Ω
tf
Fall time, output
VAUX = 5.1 V, CL = 100 µF,
RL = 10 Ω
VUSB1/2
USB1/2 output voltage
Including ripple
CL = 100 µF
4.75
0.7
1
V
Input current
VENUSB = 0 V or 5.5 V
–0.5
0.5
µA
Turnon time
CL = 100 µF, RL = 10 Ω
5
ms
Turnoff time
CL = 100 µF, RL = 10 Ω
10
ms
150
mV
1
µA
10
ms
USB ENABLE (ENUSB1, ENUSB2)
Enables threshold, USB switch
IENUSB
/FAULT1, /FAULT2
tDEG
6
Output low voltage
I/FAULT = 1 mA
Off-state current
V/FAULT = 5.5 V
/FAULT deglitch
/FAULT assertion or deassertion due
to over-current condition
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8
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Electrical Characteristics (USB1/2 Only) (continued)
over recommended operating conditions (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
ILIM1, ILIM2
IOS
Short-circuit output current
RILIM = 100 kΩ
190
380
RILIM = 40 kΩ
550
875
RILIM = 20 kΩ
1140
1700
mA
6.8 Electrical Characteristics (LDO and Reset Only)
over recommended operating conditions (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
3.8
5.1
5.25
V
3.2
3.3
3.4
V
LDO SPECIFICATIONS
Input voltage
Output voltage
Including line/load regulation
DC accuracy
±3%
Line regualtion
ILOAD: 200 mA
Line transient
500 mV step at 50 mV/μs
5
mV
15
mV
20
mV
120
mV
Dropout voltage
300
mV
Output overshoot
3%
Load regulation
Load transient
ILOAD: 0 mA - 200 mA in 1 μs
tr
Rise time, output
VAUX = 5.1 V, CL = 1 µF
tf
Fall time, output
VAUX = 5.1 V, CL = 1 µF
IOS
Short-circuit output current
PSRR
200
350
20 Hz < f < 20 kHz, IL = 100 mA
µs
1
ms
800
mA
40
dB
RESET SPECIFICATIONS
Threshold voltage
Deglitch timing
VLDOOUT rising
3.09
3.1
3.11
VLDOOUT falling
2.91
2.975
3.03
Low to high transition
150
175
200
ms
8
10
12
kΩ
Internal pullup resistance
V
6.9 Recommended External Components
over operating free-air temperature range (unless otherwise noted)
MIN
Inductor
2.2
MAX
4.7
UNIT
µH
Boost input capacitance (ceramic capacitor, X5R, 10V, 0805)
10
µF
Boost output capacitance (ceramic capacitor, X5R, 10V, 1210)
22
µF
4.7
µF
LDO input capacitance (ceramic capacitor, X5R)
RILIM
NOM
LDO output capacitance (ceramic capacitor, X5R)
0.7
Current-limit set resistor from ILIM to GND
20
1
µF
220
kΩ
6.10 Dissipation Ratings
PACKAGE
RθJA
TA ≤ 25°C POWER RATING
RGW
34.3 C°/W
2.4 W
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6.11 Typical Characteristics
14
2500
Temp . = 25°C
ENUSB 1/2 = Hi
ENLDO = Hi
Boost Switching
No load
Typical
10
IIN – Input Curre nt - mA
I O –Total Boost Output Current - mA
12
2000
1500
1000
Conservative
8
6
4
500
2
0
1.75
2.25
2.75
3.25
3.75
4.25
4.75
5.25
0
1.8
2.2
2.6
3
3.4
3.8
4.2
4.6
5
VIN – Input Voltage - V
VIN –Input Voltage - V
Figure 1. Maximum Total DC-DC Current vs Input Voltage
Figure 2. TPS2505 Typical On Input Current With No Load
5.30
V IN
VAUX – B oost Output Voltage - V
5.25
5.20
5.15
V IN = 4.95V
CAUX = 22uF
No load
IAUX = 500 mA
IAUX = 200 mA
5.10
VAUX
5.05
I AUX = 0mA
5.00
IAUX = 1000 mA
4.95
IIN
4.90
4.85
4.80
1.8
2.2
2.6
3.0
3.4
3.8
4.2
4.6
5.0
VIN – Input Voltage - V
Figure 3. Boost Output Voltage vs Input Voltage
Figure 4. Boost Start-Up After Enable – No Load
V IN
VIN = 3.0V
CAUX = 22uF
CUSB1 = 100uF
CUSB2 = 100uF
IO = 100mA
VAUX 100mV/div
V AUX
VIN = 4.95V
CAUX= 22uF
CUSB1 = 220uF
RILIM1 = 39 kO
No load
VSW 2V/div
I IN
V USB1
200us/div
Figure 5. USB1 Start-Up After Enable – No Load
8
Figure 6. Boost Output Ripple in PFM Operation
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Typical Characteristics (continued)
4
VIN = VAUX
3.5
VO(L DOOU T) – LDO Output V oltag e - V
VLDOIN
VLDOOUT
VRESET
3
2.5
2
1.5
1
0.5
0
0
100
200
300
400
500
I O( LDOOUT) – LDO Output Current - mA
Figure 8. LDO Output Voltage vs Output Current
Figure 7. LDO RESET Deglitch Time
7 Parameter Measurement Information
OUT
tf
tr
RL
90%
CL
90%
VOUT
10%
TEST CIRCUIT
VEN
50%
50%
ton
toff
90%
VOUT
10%
VOLTAGE WAVEFORMS
Figure 9. Test Circuit and Voltage Waveforms
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8 Detailed Description
8.1 Overview
This device targets applications for host-side USB devices where a 5-V power rail, required for USB operation, is
unavailable. The TPS2505 integrates the functionality of a synchronous boost converter, 3.3-V LDO with power
good RESET signal and dual USB switches into a monolithic integrated circuit so that lower-voltage rails can be
used directly to provide USB power. The TPS2505 can also be powered by an upstream USB port as it limits the
inrush current during power up to less than 100 mA to meet USB 2.0 specifications.
The boost converter is highly integrated, including the switching MOSFETs (low-side N-channel, high-side
synchronous P-channel), gate-drive and analog-control circuitry, and control-loop compensation. Additional
features include high-efficiency light-load operation, overload and short-circuit protection, and controlled
monotonic soft start. The USB switch integrates all necessary functions, including back-to-back series N-channel
MOSFETs, charge-pump gate driver, and analog control circuitry. The current-limit protection is user-adjustable
by selecting the RILIM1/2 resistors from ILIM1/2 to GND.
SW
8.2 Functional Block Diagram
STARTUP
60Ω
GATE CONTROL
AUX
SWP
SWN
CURRENT
SENSE
CURRENT
SENSE
BYPASS
CURENT
LIMIT
UVLO
LATCH
IN
DC
VREF
OSCILLATOR
EN
CHARGE
PUMP
ENLDO
ENUSB1
CURRENT
SENSE
DRIVER
LDOIN
BANDGAP
REFERENCE
(VREF )
USB1
FAULT 1
CURRENT LIMIT
LDOOUT
DEGLITCH
OVER TEMP.
DRIVER
ENUSB2
CURRENT LIMIT
RESET
175ms Delay
Falling Edge
CURRENT
SENSE
USB2
FAULT 2
DEGLITCH
3.1V
(VREF
10
ILIM2
ILIM1
referenced)
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8.3 Feature Description
8.3.1 PGND
PGND is the internal ground connection for the source of the low-side N-channel MOSFET in the boost
converter. Connect PGND to an external plane near the ground connection of the input and output capacitors to
minimize parasitic effects due to high switching currents of the boost converter. Connect PGND to GND and the
thermal pad externally at a single location to provide a star-point ground. See for further details.
8.3.2 IN
IN is the input voltage supply for the boost converter. Connect a 10-µF ceramic capacitor (minimum) from IN to
PGND. See Component Recommendations for further details on selecting the input capacitor.
8.3.3 EN
EN is a logic-level input that enables the boost converter. Pull EN above 1 V to enable the device and below 0.7
V to disable the device. EN also disables the USB switches and LDO.
8.3.4 GND
Signal and logic circuits of the TPS2505 are referenced to GND. Connect GND to a quiet ground plane near the
device. An optional 0.1-µF capacitor can be connected from VIN to GND close the device to provide local
decoupling. Connect GND and PGND to the thermal pad externally at a single location to provide a star-point
ground. See for further details.
8.3.5 ILIM1/2
Connect a resistor from ILIM1/2 to GND to program the current-limit threshold of the USB switches. Place this
resistor as close to the device as possible to prevent noise from coupling into the internal circuitry. Do not drive
ILIM1/2 with an external source. The current-limit threshold is proportional to the current through the RILIM
resistor. See Programming the Current-Limit Threshold Resistor RILIM for details on selecting the current-limit
resistor.
8.3.6 RESET
The RESET output indicates when the LDO output reaches 3.1 V. It has a 175-ms delay for deglitch in the low to
high transition. The output has in internal 10-kΩ pull-up resistor to the LDO output.
8.3.7 LDOOUT
LDOOUT is the LDO output. Internal feedback regulates LDOOUT to 3.3 V. Connect a 1-µF ceramic capacitor
from LDOOUT to PGND for compensation. See Component Recommendations for further details.
8.3.8 LDOIN
LDOIN is the input voltage supply for the LDO. Connect a 4.7-µF ceramic capacitor from LDOIN to PGND when
not powered by AUX. See Component Recommendations for further details on selecting the input capacitor.
8.3.9 ENLDO
ENLDO is a logic-level input that enables the 3.3-V LDO. Pull EN above 1 V to enable the device and below
0.7 V to disable the device. The boost converter must be enabled in order for the LDO to be enabled. The boost
converter is independent of ENLDO and continues to operate even when ENLDO disables the LDO.
8.3.10 FAULT1/2
FAULT1/2 are open-drain outputs that indicate when the USB switches are in an overcurrent or over-temperature
condition. FAULT1/2 have a fixed internal deglitch of tDEG to prevent false triggering from noise or transient
conditions. FAULT1/2 assert low if the USB switches remain in an overcurrent condition for longer than tDEG.
FAULT1/2 de-assert when the overcurrent condition is removed after waiting for the same tDEG period. Overtemperature conditions bypass the internal delay period and assert/de-assert the FAULT1/2 output immediately
upon entering or leaving an over-temperature condition. FAULT1/2 are asserted low when VAUX falls below VTRIP
(4.6 V, typical).
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Feature Description (continued)
8.3.11 ENUSB1/2
ENUSB1/2 are logic-level inputs that enable the USB switches. Pull ENUSB1/2 above 1 V to enable the USB
switches and below 0.7 V to disable the USB switches. ENUSB1/2 only enables the USB switches. The boost
converter is independent of ENUSB1/2 and continues to operate even when ENUSB disables the USB switch.
8.3.12 USB1/2
USB1/2 are the outputs of the USB switches and should be connected to the USB connectors to provide USB
power. Although the device does not require it for operation, a bulk capacitor may be connected from USB to
PGND to meet USB standard requirements. See the latest USB 2.0 specification for further details.
8.3.13 AUX
AUX is the boost converter output and provides power to the USB switches and to any additional load connected
to AUX. Internal feedback regulates AUX to 5.1 V. Connect a 22-µF ceramic capacitor from AUX to PGND to
filter the boost converter output. See Component Recommendations for further details. Additional external load
can be connected to AUX as long as the total current drawn by the USB switches and external load does not
overload the boost converter. See Determining the Maximum Allowable AUX and USB1/2 Current for details.
8.3.14 SW
SW is the internal boost converter connection of the low-side N-channel MOSFET drain and the high-side Pchannel drain. Connect the boost inductor from IN to SW close to the device to minimize parasitic effects on the
device operation.
8.3.15 Thermal Pad
The thermal pad connection is used to heat-sink the device to the printed-circuit board (PCB). The thermal pad
may not be connected externally to a potential other than ground because it is connected to GND internally. The
thermal pad must be soldered to the PCB to remove sufficient thermal energy in order to stay within the
recommended operating range of the device.
8.3.16 Boost Converter
8.3.16.1 Start-Up
Input power to the TPS2505 is provided from IN to GND. The device has an undervoltage lockout (UVLO) circuit
that disables the device until the voltage on IN exceeds 2.15 V (typical). The TPS2505 goes through its normal
start-up process and attempts to regulate the AUX voltage to 5.1 V (typical).
The boost converter has a two-step start-up sequence. During the initial startup, the output of the boost is
connected to VIN through a resistive switch that limits the startup current, ISTART, to be below 100 mA. This allows
the TPS2505 to be USB 2.0 compliant when powered by an upstream USB port. The boost output must be
unloaded during startup. ISTART charges the output capacitance on VAUX until VAUX reaches VIN – VEXIT. The
converter begins to switch once VAUX exceeds VIN – VEXIT. The initial duty cycle of the device is limited by a
closed-loop soft start that ramps the reference voltage to the internal error amplifier to provide a controlled,
monotonic start-up on VAUX. The boost converter goes through this cycle any time the voltage on VAUX drops
below VIN – VEXIT due to overload conditions or the boost converter re-enables after normal shutdown.
The USB switches are powered directly from VAUX and turns on once the UVLO of the USB switches is met
(4.3 V typical). The turnon is controlled internally to provide a monotonic start-up on VUSB1/2.
8.3.16.2 Normal Operation
The boost converter runs at a 1-MHz fixed frequency and regulates the output voltage VAUX using a pulse-width
modulating (PWM) topology that adjusts the duty cycle of the low-side N-channel MOSFET on a cycle-by-cycle
basis. The PWM latch is set at the beginning of each clock cycle and commands the gate driver to turn on the
low-side MOSFET. The low-side MOSFET remains on until the PWM latch is reset.
12
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Feature Description (continued)
Voltage regulation is controlled by a peak-current-mode control architecture. The voltage loop senses the voltage
on VAUX and provides negative feedback into an internal, transconductance-error amplifier with internal
compensation and resistor divider. The output of the transconductance-error amplifier is summed with the output
of the slope-compensation block and provides the error signal that is fed into the inverting input of the PWM
comparator. Slope compensation is necessary to prevent subharmonic oscillations that may occur in peakcurrent mode control architectures that exceed 50% duty cycle. The PWM ramp fed into the noninverting input of
the PWM comparator is provided by sensing the inductor current through the low-side N-channel MOSFET. The
PWM latch is reset when the PWM ramp intersects the error signal and terminates the pulse width for that clock
period. The TPS2505 stops switching if the peak-demanded current signal from the error amplifier falls below the
zero-duty-cycle threshold of the device.
8.3.16.3 Low-Frequency Mode
The TPS2505 enters low-frequency mode above VIN = VLFM (4.35 V typical) by reducing the dc/dc converter
frequency from 1 MHz (typical) to 250 kHz (typical). Current-mode control topologies require internal leadingedge blanking of the current-sense signal to prevent nuisance trips of the PWM control MOSFET. The
consequence of leading-edge blanking is that the PWM controller has a minimum controllable on-time (85 ns
typical) that results in a minimum controllable duty cycle. In a boost converter, the demanded duty cycle
decreases as the input voltage increases. The boost converter pulse-skips if the demanded duty cycle is less
than what the minimum controllable ON-time allows, which is undesirable due to the excessive increase in
switching ripple. When the TPS2505 enters low-frequency mode above VIN = VLFM, the minimum controllable
duty cycle is increased because the minimum controllable on-time is a smaller percentage of the entire switching
period. Low-frequency mode prevents pulse skipping at voltages larger than VLFM. The TPS2505 resumes normal
1-MHz switching operation when VIN decreases below VLFM.
One effect of reducing the switching frequency is that the ripple current in the inductor and output AUX
capacitors is increased. It is important to verify that the peak inductor current does not exceed the peak switch
current limit ISW (4.5 A typical) and that the increase in AUX ripple is acceptable during low-frequency mode.
8.3.16.4 No-Frequency Mode
The TPS2505 enters no-frequency mode above VIN = VNFM (5.05 V typical) by disabling the oscillator and turning
on the high-side synchronous PMOS 100% of the time. The input voltage is now directly connected to the AUX
output through the inductor and high-side PMOS. Power dissipation in the device is reduced in no-frequency
mode because there is no longer any switching loss and no RMS current flows through the low-side control
NMOS, which results in higher system-level efficiency. The boost converter resumes switching when VIN falls
below VNFM.
8.3.16.5 Pulsed Frequency Mode (PFM) Light-Load Operation
The TPS2505 enters the PFM control scheme at light loads to increase efficiency. The device reduces power
dissipation while in the PFM control scheme by disabling the gate drivers and power MOSFETs and entering a
pulsed-frequency mode (PFM). PFM works by disabling the gate driver when the PFM latch is set. During this
time period there is no switching, and the load current is provided solely by the output capacitor. There are two
comparators that determine when the device enters or leaves the PFM control scheme. The first comparator is
the PFM-enter comparator. The PFM-enter comparator monitors the peak demanded current in the inductor and
allows the device to enter the PFM control scheme when the inductor current falls below IINDLOW (420 mA
typical). The second comparator is the AUX-low comparator. The AUX-low comparator monitors AUX and forces
the converter out of the PFM control scheme and resumes normal operation when the voltage on AUX falls
below AUXLOW (5 V typical). The PFM control scheme is disabled during low-frequency mode when VIN > VLFM
(4.35 V typical).
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Feature Description (continued)
8.3.16.6 Overvoltage Protection
The TPS2505 provides overvoltage protection on VAUX to protect downstream devices. Overvoltage protection is
provided by disabling the gate drivers and power MOSFETs when an overvoltage condition is detected. The
TPS2505 uses a single AUX-high comparator to monitor the AUX voltage by sensing the voltage on the internal
feedback node fed into the error amplifier. The AUX-high comparator disables the gate driver whenever the
voltage on AUX exceeds the regulation point by 5% (typical). The gate driver remains disabled until the AUX
voltage falls below the 5% high OVP threshold. The overvoltage protection feature is disabled when VIN > VNFM
(5.05 V typical) to prevent unwanted shutdown.
8.3.16.7 Overload Conditions
The TPS2505 boost converter uses multiple overcurrent protection features to limit current in the event of an
overload or short-circuit condition. The first feature is the lower current-limit comparator that works on a cycle-bycycle basis. This comparator turns off the low-side MOSFET by resetting the PWM latch whenever the current
through the low-side MOSFET exceeds 4.5 A (typical). The low-side MOSFET remains off until the next
switching cycle. The second feature is the upper current-limit comparator that disables switching for eight
switching cycles whenever the current in the low-side MOSFET exceeds 6.7 A (typical). After eight switching
cycles, the boost converter resumes normal operation. The third feature is the constant-current start-up ISTART
comparator that disables switching and regulates the current through the high-side MOSFET whenever the
voltage on VAUX drops below the input voltage by VEXIT (700 mV typ). This feature protects the boost converter in
the event of an output short circuit on VAUX. ISTART also current-limit protects the synchronous MOSFET in nofrequency mode when VIN > VNFM (5.05 V typical). The converter goes through normal start-up operation once
the short-circuit condition is removed. A fourth feature is the 85% (typical) maximum-duty-cycle clamp that
prevents excessive current from building in the inductor.
8.3.16.8 Determining the Maximum Allowable AUX and USB1/2 Current
The maximum output current of the boost converter out of AUX depends on several system-level factors
including input voltage, inductor value, switching frequency, and ambient temperature. The limiting factor for the
TPS2505 is the peak inductor current, which cannot exceed ISW (3 A minimum). The cycle-by-cycle current-limit
turns off the low-side NMOS as a protection mechanism whenever the inductor current exceeds ISW. Figure 1
can be used as a guideline for determining the maximum total current at different input voltages. The typical plot
assumes nominal conditions: 2.2-µH inductor, 1-MHz/250-kHz switching frequency, nominal MOSFET onresistances. The conservative plot assumes more pessimistic conditions: 1.7-µH inductor, 925-kHz/230-kHz
switching frequency, and maximum MOSFET on-resistances. The graph accounts for the frequency change from
1-MHz to 250-kHz when VIN > VLFM (4.35 V typical) and for the no-frequency mode when VIN > VNFM (5.05 V
typical), which explains the discontinuities of the graph.
Table 1. Maximum Total DC/DC Current (IAUX + IUSB1+ IUSB2) at Common Input Voltages
INPUT VOLTAGE (V)
14
MAXIMUM TOTAL OUTPUT CURRENT (IAUX + IUSB1 + IUSB2)
CONSERVATIVE (mA)
TYPICAL (mA)
1.8
599
757
2.5
916
1113
2.7
1008
1216
3
1148
1374
3.3
1308
1536
3.6
1445
1704
4.35
1241
1730
4.5
1364
1858
4.75
1593
2093
5.05
2300
2300
5.25
2300
2300
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8.3.17 USB Switches
8.3.17.1 Overview
The TPS2505 integrates a current-limited, power-distribution switches using N-channel MOSFETs for
applications where short circuits or heavy capacitive loads are encountered. The current-limit threshold is userprogrammable from 130 mA to 1.4 A (typical) by selecting an external resistor. The device incorporates an
internal charge pump and gate-drive circuitry necessary to fully enhance the N-channel MOSFETs. The internal
gate drivers controls turnon of the MOSFETs to limit large current and voltage surges by providing built-in softstart functionality. The power switches have an independent undervoltage lockout (UVLO) circuit that disables
them until the voltage on AUX reaches 4.3 V (typical). Built-in hysteresis prevents unwanted on/off cycling due to
input voltage drop on AUX from current surges on the output of the power switch. The power switches have an
independent logic-level enable control (ENUSB1/2) that gates power-switch turnon and bias for the charge pump,
driver, and miscellaneous control circuitry. A logic-high input on ENUSB1/2 enables the drivers, control circuits,
and power switches. The enable input are compatible with CMOS, TTL, LVTTL, 2.5-V, and 1.8-V logic levels.
8.3.17.2 Overcurrent Conditions
The TPS2505 power switches respond to overcurrent conditions by limiting its output current to the IOS level.
The device maintains a constant output current and reduces the output voltage accordingly during an overcurrent
condition. Two possible overload conditions can occur. The first condition is when a short circuit or partial short
circuit is present on the output of the switch prior to device turn-on and the device is powered up or enabled. The
output voltage is held near zero potential with respect to ground, and the TPS2505 ramps the output current to
IOS. The TPS2505 power switches limit the current to IOS until the overload condition is removed or the device
begins to cycle thermally. The second condition is when a short circuit, partial short circuit, or transient overload
occurs while the device is already enabled and powered on. The current-sense amplifier is overdriven during this
time and momentarily disables the power switch. The current-sense amplifier recovers and limits the output
current to IOS. The power switches thermally cycle if an overload condition is present long enough to activate
thermal limiting in any of the foregoing cases. The power switches turns off when the junction temperature
exceeds 130°C while in current-limit. The power switches remains off until the junction temperature cools 10°C
and then restarts. The TPS2505 power switches cycles on/off until the overload is removed. The boost converter
is independent of the power-switch thermal sense and continues to operate as long as the temperature of the
boost converter remains less than 150°C and does not trigger the boost-converter thermal sense.
8.3.17.3 FAULT1/2 Response
The FAULT1/2 open-drain outputs are asserted low during an overcurrent condition that causes VUSB to fall
below VTRIP (4.6 V typical) or causes the junction temperature to exceed the shutdown threshold (130°C). The
TPS2505 asserts the FAULT1/2 signals until the fault condition is removed and the power switches resume
normal operation. The FAULT1/2 signals are independent of the boost converter or each other. The FAULT1/2
signals use an internal delay deglitch circuit (8-ms typical) to delay asserting the FAULT1/2 signals during an
overcurrent condition. The power switches must remain in an overcurrent condition for the entire deglitch period
or the deglitch timer is restarted. This ensures that FAULT1/2 are not accidentally asserted due to normal
operation such as starting into a heavy capacitive load. The deglitch circuitry delays entering and leaving fault
conditions. Overtemperature conditions are not deglitched and assert the FAULT1/2 signals immediately.
8.3.17.4 Undervoltage Lockout
The undervoltage lockout (UVLO) circuit disables the TPS2505 power switch until the input voltage on AUX
reaches the power switch UVLO turn-on threshold of 4.3 V (typical). Built-in hysteresis prevents unwanted on/off
cycling due to input-voltage drop from large current surges.
8.3.17.5 Programming the Current-Limit Threshold Resistor RILIM
The overcurrent thresholds are user programmable via external resistors. The TPS2505 uses an internal
regulation loop to provide a regulated voltage on the ILIM1/2 pins. The current-limit thresholds are proportional to
the current sourced out of ILIM1/2. The recommended 1% resistor range for RILIM1/2 is
16.1 kΩ ≤ RILIM ≤ 200 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
RILIM1/2. The following equations and Figure 10 can be used to calculate the resulting overcurrent threshold for
a given external resistor value (RILIM1/2). Figure 10 includes current-limit tolerance due to variations caused by
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temperature and process. However, the equations do not account for tolerance due to external resistor variation,
so it is important to account for this tolerance when selecting RILIM1/2. The traces routing the RILIM1/2 resistors
to the TPS2505 should be as short as possible to reduce parasitic effects on the current-limit accuracy. RILIM1/2
can be selected to provide a current-limit threshold that occurs 1) above a minimum load current or 2) below a
maximum load current.
To design above a minimum current-limit threshold, find the intersection of RILIM and the maximum desired load
current on the IOS(min) curve and choose a value of RILIM below this value. Programming the current limit above a
minimum threshold is important to ensure start up into full load or heavy capacitive loads. The resulting maximum
current-limit threshold is the intersection of the selected value of RILIM1/2 and the IOS(max) curve. To design
below a maximum current-limit threshold, find the intersection of RILIM and the maximum desired load current on
the IOS(max) curve and choose a value of RILIM1/2 above this value. Programming the current limit below a
maximum threshold is important to avoid current-limiting upstream power supplies, causing the input voltage bus
to droop. The resulting minimum current-limit threshold is the intersection of the selected value of RILIM1/2 and
the IOS(min) curve. Current-limit threshold equations (IOS):
27,570V
RILIM 1/ 2 0.93 k W
(1)
28, 235V
RILIM 1/ 2 0.998 k W
(2)
32,114V
I OS (min) (mA) =
RILIM 1/ 21.114 k W
(3)
I OS (max) (mA) =
I OS (typ ) (mA) =
1800
IAUX = 0 mA
VIN = 3 .3 V
No load on secondary USB switch
1600
I OS – US B Curre nt LImi t - mA
1400
IOS(max )
1200
1000
800
IOS(typ)
600
400
IOS(min)
200
0
20
30
40
50
60
70
80
90
100
R ILIM1/2 – USB Current Limit Resistance - kO
VIN = 3.3 V
IAUX = 0 A
Secondary USB Switch Disabled
Figure 10. USB Current-Limit Threshold vs
RILIM Overtemperature and Process
8.3.18 3.3-V LDO
The TPS2505 integrates a 3.3-V LDO with a maximum load capacity of 200 mA. The LDO can be powered by
the AUX boost output to allow operation when there is only a low voltage supply such as an alkaline battery. The
LDO will only turn on once VAUX reaches the UVLO threshold. The LDO can also be connected to be powered to
an external supply if no additional load to AUX is desired or to reduce power dissipation (in case the supply is
lower than the 5.1-V boost output). However, the boost must be enabled to allow the LDO to operate, even if
connected to a separate supply.
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8.3.19 Reset Comparator
The Reset Comparator integrated in the TPS2505 provides a power-good signal that indicates when the LDO
output has reached a 3.1-V threshold. The comparator has a 175-ms deglitch delay for the low-to-high transition
to prevent any glitches when the LDO is powering up. Hysteresis has been added to the comparator to increase
noise immunity and avoid unwanted glitches in the output during LDO transients.
8.3.20 Thermal Shutdown
The TPS2505 self-protects using two independent thermal sensing circuits that monitor the operating
temperatures of the boost converter and power switch independently and disable operation if the temperature
exceeds recommended operating conditions. The boost converter and power switches each have an ambient
thermal sensor that disables operation if the measured junction temperature in that part of the circuit exceeds
150°C. The boost converter continues to operate even if the power switch is disabled due to an overtemperature
condition.
8.3.21 Component Recommendations
The main functions of the TPS2505 are integrated and meet recommended operating conditions with a wide
range of external components. The following sections give guidelines and trade-offs for external component
selection. The recommended values given are conservative and intended over the full range of recommended
operating conditions.
8.3.21.1 Boost Inductor
Connect the boost inductor from IN to SW. The inductance controls the ripple current through the inductor. A 2.2µH inductor is recommended, and the minimum and maximum inductor values are constrained by the integrated
features of the TPS2505. The minimum inductance is limited by the peak inductor-current value. The ripple
current in the inductor is inversely proportional to the inductance value, so the output voltage may fall out of
regulation if the peak inductor current exceeds the cycle-by-cycle current-limit comparator (3 A minimum). Using
a nominal 2.2-µH inductor allows full recommended current operation even if the inductance is 20% low (1.76
µH) due to component variation. The maximum inductance value is limited by the internal compensation of the
boost-converter control loop. A maximum 4.7-µH (typical) inductor value is recommended to maintain adequate
phase margin over the full range of recommended operating conditions.
8.3.21.2 IN Capacitance
Connect the input capacitance from IN to the reference ground plane (see for connecting PGND and GND to the
ground plane). Input capacitance reduces the AC voltage ripple on the input rail by providing a low-impedance
path for the switching current of the boost converter. The TPS2505 does not have a minimum or maximum input
capacitance requirement for operation, but a 10-µF, X7R or X5R ceramic capacitor is recommended for most
applications for reasonable input-voltage ripple performance. There are several scenarios where it is
recommended to use additional input capacitance:
• The output impedance of the upstream power supply is high, or the power supply is located far from the
TPS2505.
• The TPS2505 is tested in a lab environment with long, inductive cables connected to the input, and transient
voltage spikes could exceed the absolute maximum voltage rating of the device.
• The device is operating in PFM control scheme near VIN = 1.8 V, where insufficient input capacitance may
cause the input ripple voltage to fall below the minimum 1.75-V (typical) UVLO circuit, causing device turnoff.
Additionally, it is good engineering practice to use an additional 0.1-µF ceramic decoupling capacitor close to
the IC to prevent unwanted high-frequency noise from coupling into the device.
8.3.21.3 AUX Capacitance
Connect the boost-converter output capacitance from AUX to the reference ground plane. The AUX capacitance
controls the ripple voltage on the AUX rail and provides a low-impedance path for the switching and transientload currents of the boost converter. It also sets the location of the output pole in the control loop of the boost
converter. There are limitations to the minimum and maximum capacitance on AUX. The recommended minimum
capacitance on AUX is a 22-µF, X5R or X7R ceramic capacitor. A 10-V rated ceramic capacitor is recommended
to minimize the capacitance derating loss due to dc bias applied to the capacitor. The low ESR of the ceramic
capacitor minimizes ripple voltage and power dissipation from the large, pulsating currents of the boost converter
and provides adequate phase margin across all recommended operating conditions. In some applications, it is
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desirable to add additional AUX capacitance. Additional AUX capacitance reduces transient undershoot and
overshoot voltages due to load steps and reduces AUX ripple in the PFM control scheme. Adding AUX
capacitance changes the control loop, resulting in reduced phase margin, so it is recommended that no more
than 220 µF of additional capacitance be added in parallel to the 22-µF ceramic capacitor. The combined output
capacitance on AUX and USB should not exceed 500 µF.
8.3.21.4 USB Capacitance
Connect the USB1/2 capacitances from USB1/2 to the reference ground plane. The USB1/2 capacitances are on
the outputs of the power switches and provide energy for transient load steps. The TPS2505 does not require
any USB capacitance for operation. Additional capacitance can be added on USB1/2 outputs, but it is
recommended to not exceed 220 µF to maintain adequate phase margin for the boost converter control loop.
The combined output capacitance on AUX and USB should not exceed 500 µF. USB applications require a
minimum of 120 µF on downstream facing ports.
8.3.21.5 ILIM1/2 and FAULT1/2 Resistors
Connect the ILIM1/2 resistors from ILIM1/2 to the reference ground plane. The ILIM1/2 resistors programs the
current-limit threshold of the USB power switches (see Programming the Current-Limit Threshold Resistor RILIM).
The ILIM1/2 pins are the output of internal linear regulators that provide a fixed 400-mV output. The
recommended nominal resistor value using 1% resistors on ILIM1/2 is 16.1 kΩ ≤ RILIM ≤ 200 kΩ. This range
should be adjusted accordingly if 1% resistors are not used. Do not overdrive ILIM1/2 with an external voltage or
connect directly to GND. Connect the ILIM1/2 resistors as close to the TPS2505 as possible to minimize the
effects of parasitics on device operation. Do not add external capacitance on the ILIM1/2 pins. The ILIM1/2 pins
should not be left floating. Connect the FAULT1/2 resistors from the FAULT1/2 pins to an external voltage source
such as VAUX or VIN. The FAULT1/2 pins are open-drain outputs capable of sinking a maximum current of 10 mA
continuously. The FAULT1/2 resistors should be sized large enough to limit current to under 10 mA continuously.
Do not tie FAULT1/2 directly to an external voltage source. The maximum recommended voltage on FAULT1/2 is
6.5 V. The FAULT1/2 pin can be left floating if not used.
8.4 Device Functional Modes
The device functional modes refer to the boost converter modes which are controlled by the Vin to the converter.
They include Low frequency mode, No frequency mode, Pulse Frequency Modulation (PFM) mode, and normal
mode.
In low frequency mode when the input voltage reaches 4.35 V (typical) the DC-DC switching frequency is
reduced from 1 MHz to 250 kHz. This prevents pulse skipping at voltages larger than 4.35 V. This mode is
disabled when Vin falls below 4.35 V.
No frequency mode occurs when Vin is greater than 5.05 V (typical). The oscillator is disabled at this time . This
reduces power dissipation which in turn increases efficiency. This mode is disabled when Vin falls below 5.05 V.
PFM mode is used during light loads to increase efficiency. During this period there is no switching which
reduces power dissipation, and load current is provided by output capacitor only. Two comparators control when
the converter enters and leaves PFM mode. PFM mode is disabled during low-frequency mode.
In normal mode the converter runs at 1 MHz and regulates output voltage of VAUX, using pulse width modulation
(PWM). For details on boost converter functional modes, see Boost Converter.
18
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9 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
9.1 Application Information
The TPS2505 is a USB switch device enabling a 5-V supply from a single Li-Ion battery, regulated supply, or 2to 3-cell NiCd , NiMH, or alkaline. This device is targeted toward keyboard, printer, camera, picture frame
applications, and other handheld or remote applications.
9.2 Typical Application
2.2µH
Power
Supply
1.8V – 5.25V
SW
IN
10µF
EN
RESET
3.3V Power
LDOOUT
1µF
EN_LDO
LDOIN
HUB
CONTROLLER
RFAULT 1
5V USB Power
USB1
5V Output
AUX
120µF
22µF
TPS2505
RFAULT 2
5V USB Power
USB2
FAULT 1
120µF
FAULT 2
ILIM1
RLIM1
ENUSB1
ILIM2
ENUSB2
GND
PAD
PGND
RLIM2
9.2.1 Design Requirements
For this design example, use the parameters listed in Table 2 as the input parameters.
Table 2. Design Parameters
PARAMETER
EXAMPLE VALUE
Input voltage range (VIN)
2.7 V to 4.2 V
AUX voltage (VAUX)
5.1 V (internally fixed)
Input ripple voltage (ΔVIN)
15 mV
AUX ripple voltage (ΔVAUX)
50 mV
AUX current (IAUX)
0.3 A
LDO current (ILDO) (powered from AUX)
0.1 A
USB1 current (IUSB1 )
0.5 A
USB2 current (IUSB2 )
0.1 A
Total current (ITOTAL = IAUX + ILDO + IUSB1 + IUSB2)
1A
Efficiency target, nominal
90%
Switching frequency (fSW)
1 MHz
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9.2.2 Detailed Design Procedure
9.2.2.1 Step-by-Step Design Procedure
The following design procedure provides an example for selecting component values for the TPS2505.
The following design parameters are needed as inputs to the design process.
• Input voltage range
• Output voltage on AUX
• Input ripple voltage
• Output ripple voltage on AUX
• Output current rating of AUX rail
• Output current rating of USB rail
• Nominal efficiency target
• Operating frequency
A power inductor, input and output filter capacitors, and current-limit threshold resistor are the only external
components required to complete the TPS2505 boost-converter design. The input ripple voltage, AUX ripple
voltage, and total output current affect the selection of these components.
9.2.2.2 Switching Frequency
The switching frequency of the TPS2505 is internally fixed at 1 MHz for the specified VIN range.
9.2.2.3 AUX Voltage
The AUX voltage of the TPS2505 is internally fixed at 5.1 V.
9.2.2.4 Determine Maximum Total Current (IAUX + ILDO + IUSB1 + IUSB2 )
Using Figure 1, the maximum total current at VIN = 2.7 V is 1 A using the conservative line. The design
requirements are met for this application.
9.2.2.5 Power Inductor
The inductor ripple current, Δi, should be at least 20% of the average inductor current to avoid erratic operation
of the peak-current-mode PWM controller. Assume an inductor ripple current, Δi, which is 30% of the average
inductor current and a power-converter efficiency, η, of 90%. Using the minimum input voltage, the average
inductor current at VIN = 2.7 V is:
I IN =
VAUX ´ ITOTAL 5.1V ´1A
=
= 2.1A
VIN ´h
2.7V ´ 0.9
(4)
IL
Di
I L_pk
IIN
Time
Figure 11. Waveform of Current in Boost Inductor
20
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The corresponding inductor ripple current is:
Di = 0.3 ´ I IN = 0.3 ´ 2.1A = 630mA
(5)
Verify that the peak inductor current is less than the 3-A peak switch current:
I L _ pk = I IN +
Di
= 2.42 A < 3 A
2
(6)
The following equation estimates the duty cycle of the low-side SWN MOSFET:
D=
ton
V
- VIN + I IN ´ ( RSWP + RL ) 5.1V - 2.7V + 2.1A ´ (0.1W + 0.07W)
= AUX
=
= 0.54
5.1V + 2.1A ´ (0.1W + 0.1W)
ton + toff
VAUX + VIN ´ ( RSWP + RSWN )
where
•
•
•
RSWN is the low-side control MOSFET ON-resistance
RSWP is the high-side synchronous MOSFET ON-resistance
RL is an estimate of the inductor DC resistance
(7)
The following equation calculates the recommended inductance for this design.
L=
VIN ´ D
2.7V ´ 0.54
=
= 2.31m H
f ´ Di 1´106 Hz ´ 0.63 A
(8)
The RMS inductor current is:
2
I L _ RMS = I IN
2
2
æ Di ö
æ 0.63 A ö
2
+ç
÷ = (2.1A) + ç
÷ = 2.11A
è2 3ø
è 2 3 ø
(9)
Select a Coilcraft LPS4018-222ML inductor. This 2.2-µH inductor has a saturation current rating of 2.7 A and an
RMS current rating of 2.3 A. See Component Recommendations for specific additional information.
9.2.2.6 Output AUX Capacitor Selection
The AUX output capacitor, CAUX, discharges during the PWM MOSFET on-time, resulting in an output ripple
voltage of ΔVAUX. ΔVAUX is largest at maximum load current.
C AUX =
D ´ ITOTAL
f ´ DVAUX
C AUX _ min
(10)
0.54 ´1A
=
= 10.8m F
1´106 Hz ´ 50mV
(11)
Ceramic capacitors exhibit a DC bias effect, whereby the capacitance falls with increasing bias voltage. The
effect is worse for capacitors in smaller case sizes and lower voltage ratings. X5R and X7R capacitors exhibit
less DC bias effect than Y5V and Z5U capacitors.
Select a TDK C3225X5R1A226M 22-µF, 10-V X5R ceramic capacitor to allow for a 50% drop in capacitance due
to the DC bias effect. See Component Recommendations for specific additional information.
9.2.2.7 Output USB1/2 Capacitor Selection
The USB1/2 output capacitors provide energy during a load step on the USB outputs. The TPS2505 does not
require a USB output capacitor, but many USB applications require that downstream-facing ports be bypassed
with a minimum of 120-μF, low-ESR capacitance.
Select a Panasonic EEVFK1A151P 150-μF, 10-V capacitor.
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9.2.2.8 Input Capacitor Selection
The ripple current through the input filter capacitor is equal to the ripple current through the inductor. If the ESL
and ESR of the input filter capacitor are ignored, then the required input filter capacitance is:
CIN =
630mA
Di
=
= 5.25m F
8 ´ f ´ DVIN 8 ´1´106 Hz ´15mV
(12)
Select a TDK C2012X5R1A106K 10-µF, 10-V, X5R, size 805 ceramic capacitor. The capacitance drops 20% at
3.3-V bias, resulting in an effective capacitance of 8 µF.
An additional 0.1-µF ceramic capacitor should be placed locally from IN to GND to prevent noise from coupling
into the device if the input capacitor cannot be located physically near to the device.
In applications where long, inductive cables connect the input power supply to the device, additional bulk input
capacitance may be necessary to minimize voltage overshoot. See Component Recommendations for specific
additional information.
9.2.2.8.1 Current-Limit Threshold Resistor RILIM
The current-limit threshold IOS of the power switches are externally adjustable by selecting the RILIM1/2
resistors. To eliminate the possibility of false tripping, RILIM1/2 should be selected so that the minimum tolerance
of the current-limit threshold is greater than the maximum specified USB load, IUSB.
It is also important to account for IOS shifts due to variation in VIN and IAUX. This shift due to the additional
loading in AUX can add up to ±75 mA of variation to the IOS as calculated according to Programming the CurrentLimit Threshold Resistor RILIM. Select RILIM1 so that the minimum current-limit threshold equals 600 mA to
ensure a minimum IUSB1 current-limit threshold of 525 mA. In the same way, select RILIM2 so that the minimum
current-limit threshold equals 200 mA to ensure a minimum IUSB2 current-limit threshold of 125 mA.
æ 32.114 ö
RILIM 1/ 2 = ç
÷
è I OS min ø
æ 32.114 ö
RILIM 1 = ç
÷
è 600mA ø
1
1.114
1
1.114
æ 32.114 ö
RILIM 2 = ç
÷
è 200mA ø
(13)
= 35.62k W
(14)
1
1.114
= 95.49k W
(15)
Choose the next smaller 1% resistor, which are 34.8 kΩ for RLIM1 and 95.3 kΩ for RLIM2.
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9.2.3 Application Curves
100.00
5.3
90.00
5.25
VIN = 2.7V
80.00
VIN = 5.0V
70.00
Boost Efficiency - %
VAUX – Boost Output Voltage - V
VIN =3.3V
60.00
50.00
40.00
30.00
VIN = 5 .25V
5.2
5.15
VIN = 2.8V
5.1
5.05
20.00
10.00
VIN = 5.0V
VIN =3.0 V
5
0
0.00
0
0.2
0.4
0.6
0.8
1
1.2
Figure 12. Boost Efficiency vs Output Current
VAUX
VUSB1
V USB2
200
400
600
800
1000
IAUX –Boost Output Current - A
Figure 13. Boost Output Voltage vs Load Current
VAUX
VIN = 4.95V
CAUX = 22uF
CUSB1 = 100uF
CUSB2 = 100uF
IUSB1 = 500mA
IAUX = 0mA
VLDOOUT
VRESET
VIN = 4.95V
CAUX = 22uF
LDOIN connected to AUX
IUSB2
ILDOOUT
Figure 14. Boost Load Transient Response, 500 mA - 1 A,
USB1/2 Enabled
Figure 15. LDO Load Transient Response 0 mA - 200 mA
10 Power Supply Recommendations
The device is designed to operate with an input voltage supply range from 1.8 V to 5.25 V. This input supply can
be from a single-cell Li-ion, two-cell or three-cell NiCd, NiMH or alkaline, or an externally regulated supply. If the
input supply is located more than a few inches from the TPS2505, additional bulk capacitance may be required in
addition to the ceramic bypass capacitors. An electrolytic capacitor with a value of 10 μF is a typical choice.
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11 Layout
11.1 Layout Guidelines
Layout is an important design step due to the high switching frequency of the boost converter. Careful attention
must be applied to the PCB layout to ensure proper function of the device and to obtain the specified
performance. Potential issues resulting from poor layout techniques include wider line and load regulation
tolerances, EMI noise issues, stability problems, and USB current-limit shifts. It is critical to provide a lowimpedance ground path that minimizes parasitic inductance. Wide and short traces should be used in the highcurrent paths, and components should be placed as close to the device as possible. Grounding is an important
part of the layout. The device has a PGND and a GND pin. The GND pin is the quiet analog ground of the device
and should have its own separate ground pour; connect the quiet signals to GND including the RILIM1/2 resistors
and any input decoupling capacitors to the GND pour. It is important that the RILIM1/2 resistors be tied to a quiet
ground to avoid unwanted shifts in the current-limit threshold. The PGND pin is the high-current power-stage
ground; the ground pours of the output (AUX) and bulk input capacitors should be tied to PGND. PGND and
GND should to be tied together in one location at the IC thermal pad, creating a star-point ground.
The output filter of the boost converter is also critical for layout. The inductor and AUX capacitors should be
placed to minimize the area of current loop through AUX–PGND–SW.The layout for the TPS2505EVM evaluation
board is shown in Figure 16 and should be followed as closely as possible for best performance.
11.2 Layout Example
AUX
SW
VIN
PGND
PGND
HSPORT1
PGND
LDOOUT
HSPORT2
AUX
PGND
AGND
LDOIN
PGND
AGND
PGND
VIN
HS
PO
R
T2
HSPORT1
U
OO
LD
T
VIN
Figure 16. Layout Recommendation for TPS2505 Application – 4 Layer Board
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12 Device and Documentation Support
12.1 Community Resources
The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective
contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of
Use.
TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration
among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help
solve problems with fellow engineers.
Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and
contact information for technical support.
12.2 Trademarks
E2E is a trademark of Texas Instruments.
All other trademarks are the property of their respective owners.
12.3 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.
12.4 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
13 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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26-Feb-2022
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)
TPS2505B1RGWR
ACTIVE
VQFN
RGW
20
3000
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 125
TPS
2505B1
(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