LINER LT1312CS8

LT1312
Single PCMCIA
VPP Driver/Regulator
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DESCRIPTION
FEATURES
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Digital Selection of 0V, VCC, 12V or Hi-Z
120mA Output Current Capability
Internal Current Limiting and Thermal Shutdown
Automatic Switching from 3.3V to 5V
Powered from Unregulated 13V to 20V Supply
Logic Compatible with Standard PCMCIA Controllers
1µF Output Capacitor
30µA Quiescent Current in Hi-Z or 0V Mode
VPP Valid Status Feedback Signal
No VPP Overshoot
8-Pin SO Packaging
Automatic 3.3V to 5V switching is provided by an internal
comparator which continuously monitors the PC card VCC
supply and automatically adjusts the regulated VPP output to match VCC when the VPP = VCC mode is selected.
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APPLICATIONS
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Notebook Computers
Palmtop Computers
Pen-Based Computers
Handi-Terminals
Bar-Code Readers
Flash Memory Programming
An open-collector VPP VALID output is driven low when
VPP is in regulation at 12V.
The LT1312 is available in an 8-pin SO package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
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The LT ® 1312 is a member of Linear Technology
Corporation’s family of PCMCIA drivers/regulators. The
LT1312 provides 0V, 3.3V, 5V, 12V and Hi-Z regulated
power to the VPP pin of a PCMCIA card slot from a single
unregulated 13V to 20V supply. When used in conjunction
with a PC card interface controller, the LT1312 forms a
complete minimum component-count interface for palmtop, pen-based and notebook computers. The VPP output
voltage is selected by two logic compatible digital inputs
which interface directly with industry standard PC card
interface controllers.
TYPICAL APPLICATION
Typical PCMCIA Single Slot VPP Driver
13V TO 20V
VS
PCMCIA
CARD SLOT
CONTROLLER
Linear Technology PCMCIA Product Family
VPP1
EN1 LT1312
VPP2
PCMCIA
CARD SLOT
VALID
VCC
EN0
VPPOUT
SENSE
3.3V OR 5V
GND
+
COUT
1µF
TANTALUM
LT1312 TA1
LT1312 TRUTH TABLE
EN0
EN1
0
0
1
0
0
1
0
1
1
1
X = DON’T CARE
SENSE
X
X
3.0V TO 3.6V
4.5V TO 5.5V
X
VPPOUT
0V
12V
3.3V
5V
Hi-Z
VALID
1
0
1
1
1
DEVICE
DESCRIPTION
PACKAGE
LT1312
SINGLE PCMCIA VPP DRIVER/REGULATOR
8-PIN SO
LT1313
DUAL PCMCIA VPP DRIVER/REGULATOR
16-PIN SO*
®
LTC 1314 SINGLE PCMCIA SWITCH MATRIX
14-PIN SO
LTC1315
DUAL PCMCIA SWITCH MATRIX
24-PIN SSOP
LTC1470
PROTECTED VCC 5V/3.3V SWITCH MATRIX
8-PIN SO
LTC1472
PROTECTED VCC AND VPP SWITCH MATRIX 16-PIN SO*
*NARROW BODY
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LT1312
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ABSOLUTE MAXIMUM RATINGS
PACKAGE/ORDER INFORMATION
Supply Voltage ........................................................ 22V
Digital Input Voltage ........................ 7V to (GND – 0.3V)
Sense Input Voltage ......................... 7V to (GND – 0.3V)
Valid Output Voltage ...................... 15V to (GND – 0.3V)
Output Short-Circuit Duration .......................... Indefinite
Operating Temperature ................................ 0°C to 70°C
Junction Temperature................................ 0°C to 125°C
Storage Temperature Range ................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
ORDER PART
NUMBER
TOP VIEW
GND 1
8
VPPOUT
ENO 2
7
N.C.
EN1 3
6
VS
VALID 4
5
SENSE
LT1312CS8
S8 PART MARKING
S8 PACKAGE
8-LEAD PLASTIC SO
1312
TJMAX = 125°C, θJA = 150°C/ W
Consult factory for Industrial and Military grade parts.
ELECTRICAL CHARACTERISTICS
VS = 13V to 20V, TA = 25°C, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
VPPOUT
Output Voltage
Program to 12V, IOUT ≤ 120mA (Note 1)
Program to 5V, IOUT ≤ 30mA (Note 1)
Program to 3.3V, IOUT ≤ 30mA (Note 1)
Program to 0V, IOUT = – 300µA
●
●
●
11.52
4.75
3.135
12.00
5.00
3.30
0.42
12.48
5.25
3.465
0.60
ILKG
Output Leakage
Program to Hi-Z, 0V ≤ VPPOUT ≤ 12V
●
– 10
IS
Supply Current
Program to 0V
Program to Hi-Z
Program to 12V, No Load
Program to 5V, No Load
Program to 3.3V, No Load
Program to 12V, IOUT = 120mA
Program to 5V, IOUT = 30mA
Program to 3.3V, IOUT = 30mA
●
●
●
●
●
●
●
●
ILIM
Current Limit
Program to 3.3V, 5V or 12V
VENH
Enable Input High Voltage
●
VENL
Enable Input Low Voltage
●
IENH
Enable Input High Current
2.4V ≤ VIN ≤ 5.5V
IENL
Enable Input Low Current
0V ≤ VIN ≤ 0.4V
VSEN5
VCC Sense Threshold
VPPOUT = 3.3V to 5V
●
3.60
VSEN3
VCC Sense Threshold
VPPOUT = 5V to 3.3V
●
3.60
ISEN
VCC Sense Input Current
VSENSE = 5V
VSENSE = 3.3V
VVALID TH
VPP VALID Threshold Voltage
Program to 12V
IVALID
VPP VALID Output Drive Current
Program to 12V, VVALID = 0.4V
VPP VALID Output Leakage Current
Program to 0V, VVALID = 12V
The ● denotes the specifications which apply over the full operating
temperature range.
2
µA
30
30
230
75
55
126
31
31
50
50
360
120
90
132
33
33
µA
µA
µA
µA
µA
mA
mA
mA
330
500
mA
2.4
10.5
1
V
V
V
V
10
V
0.4
V
50
µA
0.01
1
µA
4.05
4.50
V
4.00
4.50
V
38
18
60
30
µA
µA
11
11.5
V
20
●
UNITS
3.3
0.1
mA
10
µA
Note 1: For junction temperatures greater than 110°C, a minimum load
of 1mA is recommended.
LT1312
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TYPICAL PERFORMANCE CHARACTERISTICS
Quiescent Current (0V or Hi-Z Mode)
Quiescent Current (12V Mode)
500
40
30
20
10
0
5
0
15
20
10
SUPPLY VOLTAGE (V)
400
300
200
100
0
25
250
TJ = 25°C
EN0 = 5V
EN1 = 0V
RL = ∞
QUIESCENT CURRENT (µA)
TJ = 25°C
EN0 = EN1= 0V
OR
EN0 = EN1= 5V
QUIESCENT CURRENT (µA)
QUIESCENT CURRENT (µA)
50
0
5
15
20
10
SUPPLY VOLTAGE (V)
Ground Pin Current (12V Mode)
RL = 200Ω
IL = 60mA*
2
RL = 400Ω
IL = 30mA*
15
20
10
SUPPLY VOLTAGE (V)
2.0
1.5
RL = 167Ω
IL = 30mA*
1.0
RL = 500Ω
IL = 10mA*
0
25
Ground Pin Current
*FOR VPPOUT = 5V
0
5
15
20
10
SUPPLY VOLTAGE (V)
6
4
20
1.0
40 60 80 100 120 140 160
OUTPUT CURRENT (mA)
LT1312 G7
RL = 330Ω
IL = 10mA*
*FOR VPPOUT = 3.3V
0
5
15
20
10
SUPPLY VOLTAGE (V)
TJ = 25°C
VPPOUT = 0V
700
600
500
400
300
200
0
0
5
25
Current Limit
600
100
2
0
RL = 110Ω
IL = 30mA*
LT1312 G6
SHORT-CIRCUIT CURRENT (mA)
SHORT-CIRCUIT CURRENT (mA)
GROUND PIN CURRENT (mA)
8
0
1.5
Current Limit
10
25
TJ = 25°C
EN0 = 0V
EN1 = 5V
VSENSE = 3.3V
2.0
0
25
800
12
15
20
10
SUPPLY VOLTAGE (V)
LT1312 G5
16
TJ = 25°C
VS = 15V
5
0.5
LT1312 G4
14
0
Ground Pin Current (3.3V Mode)
TJ = 25°C
EN0 = 0V
EN1 = 5V
VSENSE = 5V
0.5
*FOR VPPOUT = 12V
5
0
VSENSE = 3.3V
2.5
GROUND CURRENT (mA)
GROUND CURRENT (mA)
GROUND CURRENT (mA)
6
VSENSE = 5V
50
Ground Pin Current (5V Mode)
RL = 100Ω
IL = 120mA*
4
100
LT1312 G3
2.5
8
150
LT1312 G2
10
TJ = 25°C
EN0 = 5V
EN1 = 0V
TJ = 25°C
EN0 = 0V
EN1 = 5V
RL = ∞
200
0
25
LT1312 G1
0
Quiescent Current (3.3V/5V Mode)
10
15
INPUT VOLTAGE (V)
20
25
LT1312 G8
VS = 15V
VPPOUT = 0V
500
400
300
200
100
0
0
25
50
75
100
JUNCTION TEMPERATURE (°C)
125
LT1312 G9
3
LT1312
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TYPICAL PERFORMANCE CHARACTERISTICS
VS = 15V
2.5
ENABLE INPUT CURRENT (µA)
2.0
1.5
1.0
0.5
0
30
20
10
125
25
50
75
100
JUNCTION TEMPERATURE (°C)
TJ = 25°C
VS = 15V
40
0
0
VCC Sense Threshold Voltage
5.5
0
1
5
2
3
4
ENABLE INPUT VOLTAGE (V)
VALID OUTPUT VOLTAGE (V)
VCC SENSE INPUT CURRENT (µA)
40
30
20
10
1
5
2
3
4
ENABLE INPUT VOLTAGE (V)
TJ = 25°C
VS = 15V
EN0 = 5V
EN1 = 0V
0.4
0.2
0
2.5
1.0
1.5
2.0
0.5
VALID OUTPUT CURRENT (mA)
OUTPUT VOLTAGE
CHANGE (mV)
COUT = 10µF
11.6
0.2
0.4 0.6
TIME (ms)
0.8
1.0
1.2
LT1312 G16
4
COUT = 1µF TANTALUM
40
20
100
1k
10k
FREQUENCY (Hz)
COUT = 1µF
0
COUT = 10µF
–20
0.4
0.2
COUT = 1µF
0
COUT = 10µF
–0.2
–0.4
15
13
–0.1
1M
Load Transient Response (12V)
40
20
100k
LT1312 G15
LOAD
CURRENT (mA)
0
0
60
0
10
3.0
–40
5
–0.2
80
LT1312 G14
SUPPLY
VOLTAGE (V)
OUTPUT VOLTAGE (V)
EN0 INPUT (V)
12.0
COUT = 1µF
LT1312 G12
Line Transient Response (12V)
VS = 15V
125
25
50
75
100
JUNCTION TEMPERATURE (°C)
TJ = 25°C, 12V MODE
VS = 15V + 100mVRMS RIPPLE
0.6
12V Turn-On Waveform
11.8
3.0
Ripple Rejection (12V)
LT1312 G13
12.2
SWITCH TO 3.3V
3.5
100
0.8
0
6
12.4
SWITCH TO 5V
4.0
VALID Output Voltage
1.0
TJ = 25°C
VS = 15V
0
4.5
0
RIPPLE REJECTION RATIO (dB)
VCC Sense Input Current
0
5.0
LT1312 G11
LT1312 G10
50
TJ = 25°C
VS = 15V
2.5
6
OUTPUT VOLTAGE
CHANGE (V)
INPUT THRESHOLD VOLTAGE (V)
3.0
Enable Input Current
50
VCC SENSE THRESHOLD VOLTAGES (V)
Enable Input Threshold Voltage
0
0.1
0.2 0.3
TIME (ms)
0.4
0.5
0.6
LT1312 G17
100
50
–0.1
0
0.1
0.2 0.3
TIME (ms)
0.4
0.5
0.6
LT1312 G18
LT1312
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PIN FUNCTIONS
Supply Pin: Power is supplied to the device through the
supply pin. The supply pin should be bypassed to ground
if the device is more than 6 inches away from the main
supply capacitor. A bypass capacitor in the range of 0.1µF
to 1µF is sufficient. The supply voltage to the LT1312 can
be loosely regulated between 13V and 20V. See Applications Information section for more detail.
VPPOUT Pin: This regulated output supplies power to the
PCMCIA card VPP pins which are typically tied together
at the card socket. The VPPOUT output is current limited
to approximately 330mA. Thermal shutdown provides a
second level of protection. A 1µF to 10µF tantalum output
capacitor is recommended. See Applications Information section for more detail on output capacitor considerations.
Input Enable Pins: The two digital input pins are high
impedance inputs with approximately 20µA input current
at 2.4V. The input thresholds are compatible with CMOS
controllers and can be driven from either 5V or 3.3V
CMOS logic. ESD protection diodes limit input excursions
to 0.6V below ground.
VALID Output Pin: This pin is an open-collector NPN
output which is driven low when the VPPOUT pin is in
regulation, i.e., when it is above 11V. An external 51k pullup resistor is connected between this output and the same
5V or 3.3V logic supply powering the PCMCIA compatible
control logic.
VCC Sense Pin: A built-in comparator and 4V reference
automatically switches the VPPOUT from 5V to 3.3V depending upon the voltage sensed at the PCMCIA card
socket VCC pin. The input current for this pin is approximately 30µA. For 5V only operation, connect the Sense pin
directly to ground. An ESD protection diode limits the
input voltage to 0.6V below ground.
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BLOCK DIAGRAM
LOW DROPOUT
LINEAR
REGULATOR
VS
VPPOUT
+
VCC SENSE
–
VALID
4V
EN0
+
VOLTAGE
LOGIC CONTROL
–
EN1
11V
LT1312 BD
5
LT1312
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OPERATION
The LT1312 is a programmable output voltage, lowdropout linear regulator designed specifically for PCMCIA
VPP drive applications. Input power is typically obtained
from a loosely regulated input supply between 13V and
20V (see Applications Information section for more detail
on the input power supply). The LT1312 consists of the
following blocks:
Low Dropout Voltage Linear Regulator: The heart of the
LT1312 is a PNP-based low-dropout voltage regulator
which drops the unregulated supply voltage from 13V to
20V down to 12V, 5V, 3.3V, 0V or Hi-Z depending upon the
state of the two Enable inputs and the VCC Sense input. The
regulator has built-in current limiting and thermal shutdown to protect the device, the load, and the socket
against inadvertent short circuiting to ground.
Voltage Control Logic: The LT1312 has five possible
output modes: 0V, 3.3V, 5V, 12V and Hi-Z. These five
modes are selected by the two Enable inputs and the VCC
Sense input as described by the Truth Table.
VCC Sense Comparator: When the VCC mode is selected,
the LT1312 automatically adjusts the regulated VPP output voltage to 3.3V or 5V depending upon the voltage
present at the PC card VCC supply pin. The threshold
voltage for the comparator is set at 4V and there is
approximately 50mV of hysteresis provided to ensure
clean switching between 3.3V and 5V.
VPP VALID Comparator: A voltage comparator monitors
the output voltage when the 12V mode is selected and is
driven low when the output is in regulation above 11V.
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APPLICATIONS INFORMATION
The LT1312 is a voltage programmable linear regulator
designed specifically for PCMCIA VPP driver applications.
The device operates with very low quiescent current
(30µA) in the 0V and Hi-Z modes of operation. In the Hi-Z
mode, the output leakage current falls to 1µA. Unloaded
quiescent current rises to only 55µA and 75µA when
programmed to 3.3V and 5V respectively. In addition to
the low quiescent currents, the LT1312 incorporates several protection features which make it ideal for PCMCIA
applications. The LT1312 has built-in current limiting
(330mA) and thermal shutdown to protect the device and
the socket VPP pins against inadvertent short-circuit
conditions.
an auxiliary winding to the 5V inductor in a split 3.3V/5V
LTC1142HV power supply system. A turns ratio of 1:1.8 is
used for transformer T1 to ensure that the input voltage to
the LT1312 falls between 13V and 20V under all load
conditions. The 9V output from this additional winding is
rectified by diode D2, added to the main 5V output and
applied to the input of the LT1312. (Note that the auxiliary
winding must be phased properly as shown in Figure 1.)
AUXILIARY WINDING POWER SUPPLIES
When the 12V output is activated by a TTL high on the
Enable line, the 5V section of the LTC1142HV is forced into
continuous mode operation. A resistor divider composed
of R2, R3 and switch Q3 forces an offset which is subtracted from the internal offset at the Sense – input (pin 14)
of the LTC1142HV. When this external offset cancels the
built-in 25mV offset, Burst ModeTM operation is inhibited
and the LTC1142HV is forced into continuous mode
operation. (See the LTC1142HV data sheet for further
detail). In this mode, the 14V auxiliary supply can be
Because the LT1312 provides excellent output regulation,
the input power supply may be loosely regulated. One
convenient (and economic) source of power is an auxiliary
winding on the main 5V switching regulator inductor in the
main system power supply.
LTC®1142HV Auxiliary Winding Power Supply
Figure 1 is a schematic diagram which describes how a
loosely regulated 14V power supply is created by adding
6
The auxiliary winding is referenced to the 5V output which
provides DC current feedback from the auxiliary supply to
the main 5V section. The AC transient response is improved by returning the negative lead of C5 to the 5V
output as shown.
Burst Mode is a trademark of Linear Technology Corporation.
LT1312
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APPLICATIONS INFORMATION
VIN
PDRIVE
10
D1
MBRS140
VIN
6.5V TO 18V
+
9
1/2 LTC1142HV
20
NDRIVE
5V REG
R4
22Ω
C1
68µF
Q1
Q2
D2
MBRS140
D3
MBRS130T3
T1
1.8T
30µH*
R1
100Ω
15
SENSE+
C2
1000pF
14
SENSE–
R3
18k
Q3
VN7002
C4
1000pF
14V AUXILIARY SUPPLY
+
C5
22µF
EN0
R5
0.033Ω
R2
100Ω
+
TO CARD VPP PIN
0V, 3.3V, 5V, 12V OR HI-Z
VS
VPPOUT
+
EN1 LT1312
5V
OUTPUT
VALID
1µF
SENSE
GND
C3
220µF
FROM
CARD VCC PIN
EN0
EN1
LT1312 F1
VALID
*LPE-6562-A026 DALE (605) 665-9301
Figure 1. Deriving 14V Power from an Auxiliary Winding on the LTC1142HV 5V Regulator
loaded without regard to the loading on the 5V output of
the LTC1142HV.
Continuous mode operation is only invoked when the
LT1312 is programmed to 12V. If the LT1312 is programmed to 0V, 3.3V or 5V, power is obtained directly
from the main power source (battery pack) through diode
D1. Again, the LT1312 output can be loaded without
regard to the loading of the main 5V output.
there is simply not enough time to transfer energy from the
5V primary to the auxiliary winding. For applications
where heavy 12V load currents exist in conjunction with
low input voltages (<6.5V), the auxiliary winding can be
derived from the 3.3V section instead of the 5V section of
the LTC1142. In this case, a transformer with a turns ratio
of 1:3.4 to 1:3.6 should be used in place of the 3.3V section
Figure 2 is a graph of output voltage versus output current
for the auxiliary 14V supply shown in Figure 1. Note that
the auxiliary supply voltage is slightly higher when the 5V
output is heavily loaded. This is due to the increased
energy flowing through the main 5V inductor.
AUXILIARY OUTPUT VOLTAGE (V)
17
R4 and C4 absorb transient voltage spikes associated with
the leakage inductance inherent in T1's secondary winding
and ensure that the auxiliary supply does not exceed 20V.
VIN = 8V
EN0 = HI
16
15
IOUT5V = 1A
14
IOUT5V = 0mA
13
12
11
LTC1142 Auxiliary Power from the 3.3V Output
The circuit of Figure 1 can be modified for operation with
low-battery count applications (6 cell). As the input voltage falls, the 5V duty cycle increases to the point where
0.1
1
10
100
1000
AUXILIARY OUTPUT CURRENT (mA)
LT1312 F2
Figure 2. LTC1142 Auxiliary Supply Voltage
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LT1312
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APPLICATIONS INFORMATION
on this line that may damage sensitive PCMCIA flash
memory cards if applied directly to the VPP pins.
inductor as shown in Figure 3. MOSFET Q4 and diode D4
have been added and diode D1 is no longer used. In the
previous circuit, power is drawn directly from the batteries
through D1, when the LTC1142 is in Burst Mode operation
and the VPP pin requires 3.3V or 5V. For these lower input
voltages this technique is no longer valid as the input will
fall below the LT1312 regulator’s dropout voltage. To
correct for this situation, the additional switch Q4 forces
the switching regulator into continuous mode operation
whenever 3.3V, 5V or 12V is selected.
Flash Memory Card VPP Power Considerations
PCMCIA compatible flash memory cards require tight
regulation of the 12V VPP programming supply to ensure
that the internal flash memory circuits are never subjected
to damaging conditions. Flash memory circuits are typically rated with an absolute maximum of 13.5V and VPP
must be maintained at 12V ±5% under all possible load
conditions during erase and program cycles. Undervoltage
can decrease specified flash memory reliability and overvoltage can damage the device1.
LINE POWERED SUPPLIES
In line operated products such as: desktop computers,
dedicated PC card readers/writers, medical equipment,
test and measurement equipment, etc., it is possible to
derive power from a relatively “raw” source such as a 5V
or 12V power supply. The 12V supply line in a desktop
computer however, is usually too “dirty” to apply directly
to the VPP pins of a PCMCIA card socket. Power supply
switching and load transients may create voltage spikes
Generating 14V from 5V or 12V
It is important that the 12V VPP supply for the two VPP
lines to the card be free of voltage spikes. There should be
little or no overshoot during transitions to and from the
12V level.
1See Application Note AP-357, “Power Supply Solutions for Flash Memory,”
Intel Corporation, 1992.
VIN
5.4V TO 12V
VIN
PDRIVE
24
+
23
R4
22Ω
C1
68µF
Q1
C4
1000pF
D2
MBRS1100
14V AUXILIARY SUPPLY
1/2 LTC1142
3.3V REG
NDRIVE
SENSE +
6
Q2
1
28
R3
18k
Q4
VN7002
T1
3.38T
22µH*
R1
100Ω
C2
1000pF
SENSE –
D3
MBRS130T3
D4
18V
+
C5
22µF
R4
0.033Ω
R2
100Ω
+
EN0
VPPOUT
EN1 LT1312
3.3V
OUTPUT
C3
220µF
TO CARD VPP PIN
0V, 3.3V, 5V, 12V OR Hi-Z
VS
VALID
+
1µF
SENSE
GND
FROM CARD
VCC PIN
Q3
VN7002
EN0
EN1
LT1312 F3
VALID
*LPE-6582-A086 DALE (605) 665-9301
Figure 3. Deriving Auxiliary 14V Power from an LTC1142 3.3V Regulator
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LT1312
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APPLICATIONS INFORMATION
1N5158
100µH
13.75V
5V
+
+
5
VIN
22µF
100µF
VSW
4
10k
1%
LT1172
FB
VC
GND
3
VS
EN0
2
VPPOUT
1µF
EN1 LT1312
VALID
1k
1%
1
TO CARD VPP PIN
0V, 5V, 12V OR HI-Z
+
SENSE
GND
LT1312 F4
1k
+
1µF
Figure 4. Local 5V to 15V Boost Regulator for Line Operated Applications
100µH
1N5158
13.75V
12V
+
22µF
1
+
2
VIN
100Ω
ILIM
100µF
SW1
3
100k
1%
LT1111CS8
GND
5
EN0
SENSE
SW2
4
8
VS
VPPOUT
TO CARD VPP PIN
0V, 5V, 12V OR HI-Z
+
1µF
EN1 LT1312
VALID
SENSE
GND
10k
1%
LT1312 F5
Figure 5. Local 12V to 15V Boost Regulator for Line Operated Applications
This is easily accomplished by generating a local 14V
supply from a relatively “dirty” 5V or 12V supply as shown
in Figures 4 and 5. Precise voltage control (and further
filtering) is provided by the LT1312 driver/regulator. A
further advantage to this scheme is that it adds current
limit in series with the VPP pins to eliminate possible
damage to the card socket, the PC card, or the switching
power supply in the event of an accidental short circuit.
Output Capacitance
The LT1312 is designed to be stable with a wide range of
output capacitors. The minimum recommended value is a
1µF with an ESR of 3Ω or less. The capacitor is connected
directly between the output pin and ground as shown in
Figure 6.
For applications where space is very limited, capacitors as
low as 0.33µF can be used. Extremely low ESR ceramic
capacitors with values less than 1µF must have a 2Ω
resistor added in series with the output capacitor as shown
in shown in Figure 7.
13V TO 20V
0.1µF
EN0
VS
VPPOUT
+
>1µF TANTALUM
OR ALUMINUM
EN1 LT1312
VALID
SENSE
GND
LT1312 F6
Figure 6. Recommended >1µF Tantalum Output Capacitor
13V TO 20V
0.1µF
EN0
VS
VPPOUT
EN1 LT1312
VALID
2Ω
SENSE
GND
0.33µF
CERAMIC
LT1312 F7
Figure 7. Using a 0.33µF to 1µF Output Capacitor
9
LT1312
U
W
U
U
APPLICATIONS INFORMATION
Transient and Switching Performance
Table 1. S8 Package*
The LT1312 is designed to produce minimal overshoot with
capacitors in the range of 1µF to 10µF. Larger capacitor
values can be used with a slowing of rise and fall times.
COPPER AREA
TOPSIDE
BACKSIDE
THERMAL RESISTANCE
BOARD AREA (JUNCTION-TO-AMBIENT)
2500 sq mm
2500 sq mm
2500 sq mm
120°C/W
1000 sq mm
2500 sq mm
2500 sq mm
120°C/W
The positive output slew rate is determined by the 330mA
current limit and the output capacitor. The rise time for a
0V to 12V transition is approximately 40µs, the rise time
for a 10µF capacitor is roughly 400µs (see the Transient
Response curves in the Typical Performance Characteristics section).
The fall time from 12V to 0V is set by the output capacitor
and an internal pull-down current source which sinks
about 30mA. This source will fully discharge a 1µF capacitor in less than 1ms.
Thermal Considerations
Power dissipated by the device is the sum of two components: output current multiplied by the input-output differential voltage IOUT × (VIN – VOUT), and ground pin current
multiplied by supply voltage IGND × VIN.
The ground pin current can be found by examining the
Ground Pin Current curves in the Typical Performance
Characteristics section.
Heat sinking, for surface mounted devices, is accomplished by using the heat spreading capabilities of the PC
board and its copper traces.
The junction temperature of the LT1312 must be limited to
125°C to ensure proper operation. Use Table 1 in conjunction with the typical performance graphs, to calculate the
power dissipation and die temperature for a particular
application and ensure that the die temperature does not
exceed 125°C under any operating conditions.
225 sq mm
2500 sq mm
2500 sq mm
125°C/W
1000 sq mm
1000 sq mm
1000 sq mm
131°C/W
*Device is mounted topside.
Calculating Junction Temperature
Example: given an output voltage of 12V, an input supply
voltage of 14V, an output current of 100mA, and a
maximum ambient temperature of 50°C, what will the
maximum junction temperature be?
Power dissipated by the device will be equal to:
IOUT × (VS – VPPOUT) + (IGND × VIN)
where:
IOUT = 100mA
VIN = 14V
IGND at (IOUT = 100mA, VIN = 14V) = 5mA
so,
PD = 100mA × (14V – 12V) + (5mA × 15V) = 0.275W
Using Table 1, the thermal resistance will be in the range
of 120°C/W to 131°C/W depending upon the copper area.
So the junction temperature rise above ambient will be
less than or equal to:
0.275W × 131°C/W = 36°C
The maximum junction temperature will then be equal to
the junction temperature rise above ambient plus the
maximum ambient temperature or:
TJMAX = 50°C + 36°C = 86°C.
10
LT1312
U
TYPICAL APPLICATIONS
Single Slot Interface to CL-PD6710
VLOGIC
VCC
A_VPP_PGM
13V TO 20V
51K
EN0
VS
VPPOUT
A_VPP_VCC
EN1 LT1312
VPP_VALID
VALID
VPP1
+
VPP2
1µF
PCMCIA
CARD SLOT
SENSE
GND
VCC
CIRRUS LOGIC
CL-PD6710
5V
Si9430DY OR
MMSF3P02HD
A_VCC_5
3.3V OR 5V
A_VCC_3
+
Si9933DY OR
MMDF2P01HD
10µF
LT1312 TA2
3.3V
Single Slot Interface to “365” Type Controller
VLOGIC
13V TO 20V
51k
VCC
VPP1
VS
VPPOUT
A_VPP_EN0
EN0
A_VPP_EN1
EN1 LT1312
VPP2
PCMCIA
CARD SLOT
3.3V OR 5V
A:GPI
VALID
VCC
SENSE
+
GND
1µF
“365” TYPE
CONTROLLER
5V
VS
A_VCC_EN0
IN1
G1
Si9410DY OR
MMSF5N02HD
LTC1157CS8
+
A_VCC_EN1
IN2
10µF
G2
Si9956DY OR
MMDF3N02HD
GND
3.3V
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
LT1312 TA3
11
LT1312
U
PACKAGE DESCRIPTION
Dimensions in inches (millimeters) unless otherwise noted.
S8 Package
8-Lead Plastic SOIC
0.189 – 0.197*
(4.801 – 5.004)
8
7
6
5
0.150 – 0.157*
(3.810 – 3.988)
0.228 – 0.244
(5.791 – 6.197)
1
0.010 – 0.020
× 45°
(0.254 – 0.508)
0.008 – 0.010
(0.203 – 0.254)
0.053 – 0.069
(1.346 – 1.752)
0°– 8° TYP
0.016 – 0.050
0.406 – 1.270
0.014 – 0.019
(0.355 – 0.483)
2
3
4
0.004 – 0.010
(0.101 – 0.254)
0.050
(1.270)
BSC
SO8 0294
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006 INCH (0.15mm).
RELATED PARTS
See PCMCIA Product Family table on the first page of this data sheet.
12
Linear Technology Corporation
LT/GP 0894 10K • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7487
(408) 432-1900 ● FAX: (408) 434-0507 ● TELEX: 499-3977
 LINEAR TECHNOLOGY CORPORATION 1994