Texas Instruments | TPS630250 Pin FMEA | Application notes | Texas Instruments TPS630250 Pin FMEA Application notes

Texas Instruments TPS630250 Pin FMEA Application notes
Application Report
SLVA826 – September 2016
TPS630250 Pin FMEA
Sabrina Ramalingam
ABSTRACT
The TPS630250 is a high efficiency, low quiescent current buck-boost converter suitable for applications
where the input voltage is higher or lower than the output. Output currents can go as high as 2 A in boost
mode and as high as 4 A in buck mode. The maximum average current in the switches is limited to a
typical value of 4 A. The TPS630250 regulates the output voltage over the complete input voltage range
by automatically switching between buck or boost mode, depending on the input voltage ensuring a
seamless transition between modes. The buck-boost converter is based on a fixed frequency, pulse-widthmodulation (PWM) controller using synchronous rectification to obtain highest efficiency. At low load
currents, the converter enters Power Save Mode to maintain high efficiency over the complete load
current range. There is a PFM/PWM pin allowing the choice between automatic PFM/PWM mode
operation and forced PWM operation. During PWM mode, a fixed-frequency of typically 2.5 MHz is used.
The output voltage is programmable using an external resistor divider, or is fixed internally on the chip.
The converter can be disabled to minimize battery drain. During shutdown, the load is disconnected from
the battery. The device is packaged in a 20-pin WCSP package measuring 1.766 mm x 2.086 mm and a
14-pin HotRod package measuring 2.5 mm x 3 mm.
1
Pin FMEA
This application note provides a Failure Modes and Effects Analysis (FMEA) for the device pins of the
TPS630250 Buck-Boost Converter. The failure conditions covered in this document include the typical pinby-pin failure scenarios:
• Pin short-circuited to Ground
• Pin short-circuited to TPS630250 VIN
• Pin short-circuited to TPS630250 VOUT
• Pin short-circuited to an adjacent pin
• Pin is open circuited
This application note also details how these pin conditions affect the device:
• Does the pin condition cause permanent damage?
• Is the device functional under the pin condition?
• How does the particular pin condition affect the device operation?
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1
TPS630250 Pin Configurations and Functions
2
www.ti.com
TPS630250 Pin Configurations and Functions
4
3
2
1
14
5
13
6
12
7
8
9
10
11
Figure 1. TPS630250 VQFN 14-pin RNC Package Pin-Out (Top View)
Pin Functions
Pin
I/O
Name
RNC
VOUT
12, 13, 14
PWR
FB
11
IN
Description
Buck-boost converter output
Voltage feedback of adjustable version, must be connected to VOUT on fixed output voltage
versions
L2
1
PWR
PFM/PWM
10
IN
PGND
2
PWR
Power Ground
GND
9
PWR
Analog Ground
L1
3
PWR
Connection for inductor
EN
8
IN
VIN
4, 5, 6
PWR
Supply voltage for power stage
VINA
7
PWR
Supply voltage for control stage
2
Connection for inductor
Set low for PFM mode, set high for forced PWM mode. It must not be left floating
Enable input. Set high to enable and low to disable. It must not be left floating.
TPS630250 Pin FMEA
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FMEA Analysis
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3
FMEA Analysis
Table 1. Pin FMEA Analysis for Pin Short Circuit to Ground
Pin
Number
Short to GND
Name
Damage
Functional
Comments
NO
NO
Output voltage goes down to 0 V; high current consumption can
affect long-term reliability
PGND
NO
YES
No effect
L1
YES
NO
Significant failure currents present
4
VIN
NO
YES
Device shuts down (UVLO) - equivalent to battery short
5
VIN
NO
YES
Device shuts down (UVLO) - equivalent to battery short
6
VIN
NO
YES
Device shuts down (UVLO) - equivalent to battery short
7
VINA
NO
NO
Device shuts down (UVLO) - equivalent to battery short - if VINA
has an external power supply the device shuts down
8
EN
NO
NO
Device is disabled
9
GND
NO
YES
No effect
10
PFM/PWM
NO
NO
Device operates in PFM mode
11
FB
NO
YES
Device cannot regulate to the target voltage
12
VOUT
NO
NO
Short-circuit protection is triggered
13
VOUT
NO
NO
Short-circuit protection is triggered
14
VOUT
NO
NO
Short-circuit protection is triggered
1
L2
2
3
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FMEA Analysis
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Table 2. Pin FMEA Analysis for Pin Short Circuit to VIN
Pin
4
Short to VIN
Number
Name
Damage
Functional
1
L2
YES
NO
Significant failure currents present
Comments
2
PGND
NO
YES
Device shuts down (UVLO) - equivalent to battery short
3
L1
YES
NO
Current sensor shorted, no current regulation possible
4
VIN
NO
YES
No effect
5
VIN
NO
YES
No effect
6
VIN
NO
YES
No effect
7
VINA
NO
NO
No effect
8
EN
NO
NO
Device always enabled
9
GND
NO
YES
Device shuts down (UVLO) - equivalent to battery short
10
PFM/PWM
NO
NO
Device operates in PWM mode
11
FB
NO
YES
Device cannot regulate to the targeted voltage
12
VOUT
NO
NO
Depending on PFM/PWM, VIN and VOUT settings, the device operates
in current limit or remains idle or keeps switching with no VOUT
regulation
13
VOUT
NO
NO
Depending on PFM/PWM, VIN and VOUT settings, the device operates
in current limit or remains idle or keeps switching with no VOUT
regulation
14
VOUT
NO
NO
Depending on PFM/PWM, VIN and VOUT settings, the device operates
in current limit or remains idle or keeps switching with no VOUT
regulation
TPS630250 Pin FMEA
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FMEA Analysis
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Table 3. Pin FMEA Analysis for Pin Short Circuit to VOUT
Pin
Number
Short to VOUT
Name
Damage
Functional
Comments
Significant failure currents present can affect long-term reliability;
regulates in buck PWM mode
1
L2
NO
YES/NO
2
PGND
NO
NO
Short-circuit protection is triggered
3
L1
NO
NO
Significant failure currents present can affect long-term reliability
4
VIN
NO
NO
Depending on PFM/PWM, VIN and VOUT settings, the device operates
in current limit or remains idle or keeps switching with no VOUT
regulation
5
VIN
NO
NO
Depending on PFM/PWM, VIN and VOUT settings, the device operates
in current limit or remains idle or keeps switching with no VOUT
regulation
6
VIN
NO
NO
Depending on PFM/PWM, VIN and VOUT settings, the device operates
in current limit or remains idle or keeps switching with no VOUT
regulation
7
VINA
NO
NO
Depending on PFM/PWM, VIN and VOUT settings, the device operates
in current limit or remains idle or keeps switching with no VOUT
regulation
8
EN
NO
NO
Device cannot be started
9
GND
NO
NO
Short-circuit protection is triggered
10
PFM/PWM
NO
YES
Device operates in PWM mode
11
FB
NO
NO
Device cannot regulate to targeted voltage
12
VOUT
NO
NO
No effect
13
VOUT
NO
NO
No effect
14
VOUT
NO
NO
No effect
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FMEA Analysis
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Table 4. Pin FMEA Analysis for Pin Short Circuit to an Adjacent Pin
Pin
Number
1
2
3
4
5
6
L1
11
12
13
14
Comments
Output voltage goes down to 0 V; high current consumption
can affect long-term reliability
NO
NO
12/13/14
VOUT
NO
Yes/NO
10
PFM/PWM
NO
YES
Device operates in PWM mode
1
L2
NO
NO
Output voltage goes down to 0 V; high current consumption
can affect long-term reliability
3
L1
YES
NO
Significant failure currents present
Significant failure currents present can affect long-term
reliability; regulates in buck PWM mode
9
GND
NO
YES
No effect
2
PGND
YES
NO
Significant failure currents present
4/5/6
VIN
YES
NO
Current sensor shorted, no current regulation possible
8
EN
NO
NO
Device cannot start
3
L1
YES
NO
Current sensor shorted, no current regulation possible
5
VIN
NO
YES
No effect
4/6
VIN
NO
YES
No effect
3
L1
YES
NO
Current sensor shorted, no current regulation possible
5
VIN
NO
YES
No effect
7
VINA
NO
YES
No effect
3
L1
YES
NO
Current sensor shorted, no current regulation possible
6
VIN
NO
NO
No effect
8
EN
NO
YES
Device is enabled
3
L1
NO
NO
Device cannot start
7
VINA
NO
YES
Device is enabled
9
GND
NO
NO
Device is disabled
2
PGND
NO
YES
No effect
VIN
VIN
EN
Functional
PGND
VIN
8
Short to Adjacent
Damage
2
PGND
VINA
10
6
L2
7
9
Adjacent Pin
Name
GND
PFM/PWM
8
EN
NO
NO
Device is disabled
10
PFM/PWM
NO
Yes
Device operates in PFM mode
1
L2
NO
NO
Buck: operates in PWM mode; Boost: changes between PFM
and PWM mode
9
GND
NO
Yes
Device operates in PFM mode
11
FB
YES
YES
Operates in PWM mode
10
PFM/PWM
YES
YES
Operates in PWM mode
12
VOUT
NO
NO
Device cannot regulate to targeted voltage
1
L2
NO
Yes/NO
11
FB
NO
NO
Device cannot regulate to targeted voltage
13
VOUT
NO
YES
No effect
1
L2
NO
Yes/NO
12/14
VOUT
NO
YES
1
L2
NO
Yes/NO
13
VOUT
NO
YES
FB
VOUT
VOUT
VOUT
Significant failure currents present can affect long-term
reliability; regulates in buck PWM mode
Significant failure currents present can affect long-term
reliability; regulates in buck PWM mode
No effect
Significant failure currents present can affect long-term
reliability; regulates in buck PWM mode
No effect
TPS630250 Pin FMEA
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FMEA Analysis
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Table 5. Pin FMEA Analysis for Pin Open Circuit
Pin
Open Circuit
Number
Name
Damage
Functional
1
L2
NO
NO
Open circuit, device not switching
Comments
2
PGND
NO
YES
Device is not functional as no PGND is present
3
L1
NO
NO
Open circuit, device not switching
4
VIN
NO
YES
No effect second connection present
5
VIN
NO
YES
No effect second connection present
6
VIN
NO
YES
No effect second connection present
7
VINA
NO
YES
Device suffers in noise performances
8
EN
NO
NO
Device enable cannot be controlled
9
GND
NO
NO
No VOUT regulation possible
10
PFM/PWM
NO
YES
PFM/PWM cannot be controlled
11
FB
NO
NO
No VOUT regulation possible, can affect long-term reliability
12
VOUT
NO
YES
No effect second connection present
13
VOUT
NO
YES
No effect second connection present
14
VOUT
NO
YES
No effect second connection present
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TPS630250 Pin FMEA
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