TC1266
200mA PCI LDO
Features
•
•
•
•
•
•
•
•
•
Glitch Free Transition Between Input Sources
Automatic Input Source Selection
External PMOS Bypass Switch Control
Built-in 5V Detector
1% Regulated Output Voltage Accuracy
200mA Load Current Capability
Kelvin Sense Input
Low Dropout Voltage (240mV @ Full Load)
Low Ground Current, Independent of Load
General Description
The TC1266 is an application-specific, low dropout
regulator (LDO), specifically intended for use in PCI
peripheral card applications complying with PCI Power
Management (PCI 2.0). It provides an uninterrupted,
3.3V, 200mA (max) output voltage when the main (5V)
or auxiliary (3.3V) input voltage supplies are present.
The TC1266 consists of an LDO, a voltage threshold
detector, external switchover logic and gate drive
circuitry. It functions as a conventional LDO as long as
the voltage on the main supply input (V
IN
) is above the
lower threshold (3.90V typical). Should the voltage on
V
IN
fall below the lower threshold, the LDO is disabled
and an external P-channel MOSFET is automatically
turned on, connecting the auxiliary supply input to
V
OUT,
and ensuring an uninterrupted 3.3V output. The
main supply is automatically selected, if both the main
and auxiliary input supplies are present, and transition
from one input supply to the other is ensured glitch-
free. High integration, automatic secondary supply
switchover, Kelvin sensing, and small size make the
TC1266 the optimum LDO for PCI 2.0 applications.
Applications
•
•
•
•
PCMCIA
PCI
Network Interface Cards (NICs)
Cardbus
TM
Technology
Device Selection Table
Part Number
Package
Junction
Temp. Range
-5°C to +125°C
TC1266VOA 8-Pin SOIC (Narrow) -5°C to +125°C
TC1266VUA
8-Pin MSOP
Functional Block Diagram
V
IN
V
AUX
Package Type
8-Pin SOIC
V
IN
NC
V
AUX
GND
1
2
3
4
8
D
R
V
OUT
SENSE
NC
Detect
D
R
Bandgap
Reference
TC1266
7
6
5
–
E/A
+
GND
V
OUT
SENSE
8-Pin MSOP
V
IN
NC
V
AUX
GND
1
2
3
4
8
7
D
R
V
OUT
SENSE
NC
TC1266
6
5
2002 Microchip Technology Inc.
DS21377B-page 1
©
TC1266
1.0
ELECTRICAL
CHARACTERISTICS
*Stresses above 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 above those indicated in the
operation sections of the specifications is not implied.
Exposure to Absolute Maximum Rating conditions for
extended periods may affect device reliability.
Absolute Maximum Ratings*
Input Supply Voltage (V
IN
).............. -0.5V to +7V (Max)
Auxiliary Supply Voltage (V
AUX
) ..... -0.5V to +7V (Max)
LDO Output Current (I
OUT
)................................ 200mA
Thermal Impedance,
Junction-to-Ambient (θ
JA
)............130°C/W for SOIC
ESD Rating .......................................................... 2 KV
Operating Temperature Range (T
A
)........ -5°C to +70°C
Storage Temperature Range (T
STG
) ...-65°C to +150°C
TC1266 ELECTRICAL SPECIFICATIONS
Electrical Characteristics:
T
A
= +25°C, V
IN
= 5V, V
AUX
= 3.3V, I
OUT
= 0.1mA, C
OUT
= 4.7µF, unless otherwise noted.
Boldface
type specifications apply over full operating temperature range.
Symbol
V
IN
I
GND
I
VIN
V
AUX
I
Q(AUX)
Parameter
Supply Voltage
Ground Current
Reverse Leakage from V
AUX
Supply Voltage
Quiescent Current
Min
4.3
—
—
—
3.0
—
—
—
—
I
VAUX
V
TH(LO)
V
HYST
V
TH(HI)
V
OUT
Reverse Leakage from V
IN
5V Detector
Low Threshold Voltage
5V Detector
Hysteresis Voltage
5V Detector
High Threshold Voltage
LDO Output Voltage
—
—
3.75
—
200
—
4.0
—
3.234
3.000
I
OUT
REG
(LINE)
REG
(LOAD)
Note
1:
2:
3:
4:
5:
6:
Typ
5.0
230
260
-0.1
3.3
50
—
60
—
-0.1
3.90
—
260
—
4.15
—
3.300
—
—
—
0.05
—
0.05
—
Max
5.5
450
500
-1.0
3.6
70
100
80
120
-1.0
—
4.05
—
300
—
4.30
—
3.366
—
—
—
0.5
—
0.5
Units
V
µA
µA
V
µA
µA
µA
V
mV
V
V
V
AUX
= 0V
Test Conditions
V
AUX
= 0V
(Note 6)
V
AUX
= 3.3V
(Note 6)
V
AUX
= 3.6V, V
IN
= 0V, I
OUT
= 0mA
V
IN
= 0V, I
OUT
= 0mA
V
IN
= 5V, I
OUT
= 0mA
V
IN
= 5,5V, V
AUX
= 0V, I
OUT
= 0mA
V
IN
Falling
(Notes 2, 3)
(Notes 2, 3)
V
IN
Rising
(Notes 2, 3)
I
OUT
= 20mA
4.3V
≤
V
IN
≤
5.5V, 0mA
≤
I
OUT
≤
200mA
3.75V
≤
V
IN
≤ 4.3V,
0mA
≤
I
OUT
≤
200mA
(Note 4)
Output Current
Line Regulation
Load Regulation
200
—
-0.5
—
-0.5
mA
%
%
V
IN
= 4.3V to 5.5V
I
OUT
= 0.1mA to 200mA
Ensured by design.
See 5V Detect Thresholds, Figure 4-1.
Recommended source impedance for 5V supply:
≤
0.25Ω. This will ensure that I
OUT
x R
SOURCE
< V
HYST
, thus avoiding D
R
toggling during
5V detect threshold transitions.
In Application Circuit, Figure 3-1.
See Timing Diagram, Figure 4-2.
Ground Current is independent of I
LOAD
.
©
DS21377B-page 2
2002 Microchip Technology Inc.
TC1266
TC1266 ELECTRICAL SPECIFICATIONS
(CONTINUED)
Electrical Characteristics:
T
A
= +25°C, V
IN
= 5V, V
AUX
= 3.3V, I
OUT
= 0.1mA, C
OUT
= 4.7µF, unless otherwise noted.
Boldface
type specifications apply over full operating temperature range.
Symbol
V
DR
Parameter
Drive Voltage
Min
V
IN
- 0.2
V
IN
- 0.3
—
—
I
DR(PK)
t
DH
t
DL
Note
1:
2:
3:
4:
5:
6:
Typ
V
IN
- 0.1
—
35
—
—
—
4
—
0.6
—
Max
—
—
150
200
—
—
—
8
1.5
3.0
Units
V
mV
mA
µsec
µsec
Test Conditions
4.3V
≤
V
IN
≤
5.5V, I
DR
= 200µA
V
IN
< V
TH(LO)
, I
DR
= 200µA
Sinking: V
IN
= 3.75V, V
DR
= 1V;
Sourcing: V
IN
= 4.3V, V
IN
– V
DR
= 2V
C
DR
= 1.2nF, V
IN
ramping up,
measured from V
IN
= V
TH(HI)
to V
DR
= 2V
C
DR
= 1.2nF, V
IN
ramping down,
measured from V
IN
= V
TH(LO)
to V
DR
= 2V
Peak Drive Current
Drive High Delay
(Notes 1, 5)
Drive Low Delay
(Notes 1, 5)
7
6
—
—
—
—
Ensured by design.
See 5V Detect Thresholds, Figure 4-1.
Recommended source impedance for 5V supply:
≤
0.25Ω. This will ensure that I
OUT
x R
SOURCE
< V
HYST
, thus avoiding D
R
toggling during
5V detect threshold transitions.
In Application Circuit, Figure 3-1.
See Timing Diagram, Figure 4-2.
Ground Current is independent of I
LOAD
.
2002 Microchip Technology Inc.
DS21377B-page 3
©
TC1266
2.0
PIN DESCRIPTIONS
The descriptions of the pins are listed in Table 2-1.
TABLE 2-1:
Pin No.
(8-Pin SOIC)
(8-Pin MSOP)
1
2
3
4
5
6
7
8
PIN FUNCTION TABLE
Symbol
V
IN
NC
V
AUX
GND
NC
SENSE
V
OUT
D
R
Description
Main input supply for the TC1266, nominally 5V.
Not connected.
Auxiliary input supply, nominally 3.3V.
Logic and power ground.
Not connected.
Sense pin for V
OUT
. Connect to V
OUT
at the load to minimize voltage drop across PCB traces.
LDO 3.3V output.
Driver output for external P-channel MOSFET pass element.
3.0
DETAILED DESCRIPTION
APPLICATION CIRCUIT
Q1
FIGURE 3-1:
U1
5V
1
V
IN
D
R
8
2 NC
3.3V
C2
4.7µF
C1
0.1µF
C3
0.1µF
3 V
AUX
4
GND
TC1266
V
OUT
7
6
C4
4.7µF
C5
0.1µF
3.3V
SENSE
NC 5
NOTE:
External switch (Q1): use Motorola MGSF1P02ELT1 or equivalent
(PMOS, typical Gate Threshold Voltage = 1V, typical R
DS(ON)
= 0.4Ω at VGS = 2.5V)
©
DS21377B-page 4
2002 Microchip Technology Inc.
TC1266
4.0
4.1
THERMAL CONSIDERATIONS
Thermal Shutdown
Equation 4-1 can be used in conjunction with
Equation 4-2 to ensure regulator thermal operation is
within limits. For example:
Given:
V
IN
MAX
= 5V ± 5%
V
OUT
MIN
= 3.217V
I
LOAD
MAX
= 200mA
T
J
MAX
T
A
MAX
θ
JA
= 125°C
= 70°C
= 130°C/W (SOIC)
Integrated thermal protection circuitry shuts the
regulator off when die temperature exceeds 160°C.
The regulator remains off until the die temperature
drops to approximately 150°C.
4.2
Power Dissipation
The amount of power the regulator dissipates is
primarily a function of input and output voltage, and
output current. The following equation is used to
calculate worst case actual power dissipation:
Find: 1. Actual power dissipation
2. Maximum allowable dissipation
Actual power dissipation:
P
D
≈
(V
IN
MAX
– V
OUT
MIN
)I
LOAD
MAX
= (5.25V - 3.217V) 200mA
= 407mW
Maximum allowable power dissipation:
P
D
MAX
= (T
J
MAX
– T
A
MAX
)
θ
JA
= (125 – 70)
130
= 423mW
In this example, the TC1266 dissipates a maximum of
407mW; below the allowable limit of 423mW.
EQUATION 4-1:
P
D
≈
(V
IN
MAX
– V
OUT
MIN
)I
LOAD
MAX
Where:
P
D
=
V
IN
MAX
=
V
OUT
MIN
=
I
LOAD
MAX
=
Worst case actual power dissipation
Maximum voltage on V
IN
Minimum regulator output voltage
Maximum output (load) current
The
maximum
allowable
power
dissipation
(Equation 4-2) is a function of the maximum ambient
temperature (T
A
MAX
), the maximum allowable die
temperature (T
J
MAX
) and the thermal resistance from
junction-to-air (θ
JA
).
EQUATION 4-2:
P
D
MAX
= (T
J
MAX
– T
A
MAX
)
θ
JA
Where all terms are previously defined.
2002 Microchip Technology Inc.
DS21377B-page 5
©
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