PCMCIA Card and Card Socket Power Management

Application Note 60
January 1995
PCMCIA Card and Card Socket Power Management
Doug La Porte
INTRODUCTION
Most portable computers have built-in sockets to accept
small PC cards for use as extended memories, fax modems, network interfaces, wireless communicators and a
wide assortment of other functions. The Personal Computer Memory Card International Association (PCMCIA)
has released specifications that outline the general power
requirements for these cards.
The specification calls for an unusual amount of voltage
switching. Both supplies are switchable to different voltages to accommodate a wide range of card types. The VCC
supply must provide either 3.3V or 5V. The VPP supply
must source 12V, 3.3V, 5V, 0V and realize a high impedance state. These diverse, specific requirements call for
specialized solutions.
PC card designers may want to design their cards to
require the VCC supply only. Flash memory card designers who need to ensure a clean VPP supply may generate
their own 12V on the card. Type I PC cards, at an outside
thickness of 3.3mm, require ultra-thin highly efficient
circuitry. The DC/DC converter IC, inductor, capacitors
and diodes are critical components that require unique
design to meet the stringent height requirements.
PCMCIA SOCKET POWER MANAGEMENT
PCMCIA Specification Voltage Switching Requirements
Host power delivery to the PC card socket flows through
two paths: the main VCC supply pins and the VPP programming pins. Figure 1 shows a typical system’s connections.
The VCC supply must be capable of providing up to 1A at
either 3.3V or 5V. The latest specification has provisions for
a future voltage referred to as X.XV (X.X to be less than
3.3V). The actual voltage value will be determined at a later
date. The VPP supply must source 12V at up to 120mA, the
VCC voltage at lesser currents, 0V and realize a high
impedance state.
5V
PCMCIA
CONTROLLER
3.3V 12V
PCMCIA SOCKET
VOLTAGE
SWITCHING
MATRIX
0V/VCC/12V/Hi-Z
(120mA MAX)
3.3V/5V/OFF
(1A MAX)
VPP1
VPP2
VCC1
VCC2
PCMCIA
CARD
SOCKET
GND (4 PINS)
AN60 • F01
Figure 1. Typical Single Socket Power Management
The PCMCIA specification requires the VCC voltage to be
selectable from 3.3V, 5V or an off state. The X.X voltage of
the future will not be addressed until the voltage has been
defined. The specification does not outline any current draw
requirements. The industry standard maximum current
that the socket will support is 1A. This number is derived
from the maximum connector rating of 500mA per pin and
assumes both pins in good condition with current being
shared equally. In practice this amount of current draw is
exceptional and should not be encouraged for continuous
use. One of the most stringent actual requirements is a Type
III hard disk drive card. Present hard drives require 5V at
600mA to 820mA for a short duration during spin-up with
current draw dropping to 300mA to 420mA during read and
write operations.
The PCMCIA specification requires the VPP voltage to be
selectable from 0V, VCC, 12V or a high impedance state.
Again, the specification does not outline any current draw
requirements. The VPP voltage’s primary use is for programming flash memory with the current requirements
derived from the flash memory needs. A single byte wide
flash memory device will require 12V at 30mA for write or
erase operations. The PC card bus is 16-bits wide necessitating two flash devices being written to at the same instant.
A standard flash memory card will require at least 60mA of
current during write or erase operations. Many flash cards
designed as solid state disc drives, often referred to as ATA
, LTC and LT are registered trademarks of Linear Technology Corporation.
AN60-1
Application Note 60
flash drives, will have two 16-bit wide banks of memory to
facilitate simultaneous writing and erasing. This speeds
card operation but will double the current requirement.
These cards will draw 120mA while writing/erasing.
Additional Practical Considerations
While the PCMCIA specification provides the basis for the
voltage switching requirements, there are many real world
requirements that must also be considered. These issues
include switch resistance, inrush current during voltage
switching, voltage ringing during switching, short-circuit
protection and cost effectiveness as a system, not just the
function.
The MOSFET switch on-resistance RDS(ON), should be low
enough to maintain the correct voltage tolerance at the
card input. The most critical case is when the VCC is 5V.
The specification requires the voltage to be 5V ±5%
(±0.25V). The most stringent requirement would be during hard disk drive spin-up where the card can pull up to
820mA. Many systems will have a main supply with a
tolerance of ±2%. When the main power supply is at its
minimum value of 4.90V, this leaves only 0.150V maximum voltage drop across the switch. To ensure that the
hard drive will spin-up without dropping the voltage below
4.75V the switch on-resistance must be less than 0.183Ω.
To ensure operation at the 1A limit the switch on-resistance must be less than 0.150Ω. It is common practice to
raise the nominal voltage slightly above 5V to relax the
voltage tolerance. For example, raising the nominal voltage to 5.10V will allow the tolerance to increase to ±4%.
The nature of PC cards and portable systems requires the
card being powered on and off as needed to conserve
power. With many PC cards drawing up 2W, this power
up/down sequencing can put demanding transient requirements on your system power supply. More important than the static current requirement of the card is the
dynamic requirement due to input capacitance. Cards will
have up to 150µF of input capacitance. This large capacitor
coupled with a fast switch will pull many amperes of
current from the system supply. With a simple switch the
only factors limiting the inrush current are the switch’s
rise time, the switch’s RDS(ON), the card input capacitor
value and the input capacitor’s equivalent series resis-
AN60-2
tance (ESR). Many large input capacitors will be for oncard switching power supplies and will likely have an ESR
in the 0.1Ω range. As noted above, the switch’s RDS(ON)
would be 0.183Ω or lower. These low resistance values
will do little to limit the inrush current. In a simple switch,
this leaves rise time as the only parameter that can keep
inrush current to manageable levels. More sophisticated
switches will also employ current limiting. Many simple
switches, without current limiting, have rise times as fast
as 100µs. This gives a peak current of over 7A! With the
rise time slowed to 500µs, the peak current is down to a
reasonable 1.5A. Current limiting will protect the system
against even larger input capacitors. To make the transient
response of the system supply manageable, the PCMCIA
switch should have a controlled, slowed rise time and
current limiting. Slowed rise time and current limiting
eliminate inadvertent system resets triggered by a momentary pull on the main supply.
The VPP lines also require slowed switch rise times. The
VPP pins are for flash memory programming and will not
have excessive input capacitance. As such, inrush current
is not a major issue. The switch times must be slowed to
avoid voltage ringing and overshoot at the flash memory
device. The flash memory device has a 14V absolute
maximum input voltage specification. Voltages beyond this
limit, for as little as 20ns, can permanently damage the
device. If the switch has a fast rise time there will be ringing
due to the trace and connector inductance. It will take only
a couple of inches of trace to form enough inductance to
cause excessive ringing. For this reason the VPP switch
must have a controlled, slowed rise time.
The PCMCIA socket will usually have a small door to protect
it from unwanted objects entering. Other than this door, the
socket pins are exposed to the outside world. The exposed
socket pins are vulnerable to being shorted by foreign
objects such as paper clips. The card installer is generally
not trained and may have little or no technical knowledge.
Some users may attempt to install damaged, possibly
short-circuited cards. In short, once the product is in the
hands of the consumer, the designer and manufacturer
have little control over its use and abuse. To ensure a robust
system and satisfied customer, PCMCIA switch protection
features such as current limiting and thermal shutdown are
Application Note 60
a necessity. These features will protect the card, socket and
main system power supply.
System design issues also deserve consideration. The
switch matrix’s digital interface should connect directly to
industry standard controllers. This may seem a trivial issue
but additional glue logic will add unnecessary cost and
consume real estate. The other system issue is the availability of a 12V supply. Some systems have a general purpose
12V supply in the system design from the start and there are
only minor issues to consider. The flash memory devices
have a strict 12V ±0.6V specification for guaranteed programming. When the main 12V supply tolerance is added
to the switch resistance, the main supply tolerance must be
very tight. The voltage should also be free of excessive
noise spikes that may exceed the flash device maximum
voltage limit. In addition, some switch matrix devices need
a constant 12V supply to operate while those incorporating
on-chip charge pumps require 12V only during flash
memory programming. Deriving the clean 12V supply in a
simple, cost effective manner is a significant part of the
design that must not be overlooked.
LTC1472: Fully Protected Switch Matrix
The LTC ®1472 is a complete VCC and VPP switch matrix
that addresses all the PCMCIA socket switching needs. The
part is fully integrated with no need for external switching
FETs. VCC switch RDS(ON) is below 0.120Ω to support the
current requirement of up to 1A. The VCC output is switched
between 3.3V, 5V and high impedance. VPP 12V switch
RDS(ON) is below 0.5Ω to support its current requirement.
The VPP output pin is switched between 0V,VCC, 12V and
high impedance. The VCC logic inputs are exclusively OR’d
to allow direct interfacing with both logic high and logic low
industry standard controllers without any external glue
logic. The LTC1472 is available in the space saving narrow
16-pin SOIC package.
The LTC1472 features SafeSlotTM protection. Built-in
SafeSlot current limiting and thermal shutdown features
are vital to ensuring a robust and reliable system. The VCC
current limit is above the 1A socket limit to maintain
compatibility with all existing cards yet provide protection
against inadvertent short circuiting. The VPP current limit
is above 200mA to also maintain compatibility and provide
protection. All switches are break-before-make type with
controlled rise and fall times for minimal system supply
impact. The LTC1472’s slowed rise time combined with the
current limiting minimizes inrush current to manageable
levels. Slowed rise time on the VPP switch ensures smooth
voltage transitions without damaging ringing and overshoot.
Figure 2 shows a typical LTC1472 application used in
conjunction with the LT ®1301 to supply the 12V input. The
LT1301 is optional. If your system already has a suitable
12V supply it can be directly connected to the VPPIN pin.
You should be cautious when using a general purpose 12V
supply. Make certain that it does not have spikes or transients exceeding the flash memory 14V maximum voltage
rating and that the regulation is within the 5% flash memory
tolerance.
D1
MBRS130LT3
L1
22µH
+ C1
47µF
3.3V
OR 5V
+ C2
VCC
SELECT
SW
SENSE
33µF
LT1301
SHDN
ILIM
PGND
GND
NC
3.3V
5V
5VIN VDD 3VIN
VPPIN
SHDN
VPPOUT
0.1µF
LTC1472
PCMCIA
CONTROLLER
PCMCIA
CARD
SOCKET
VPP EN0
VPP EN1 VCC(IN)
VCC(OUT)
VCC EN0
VCC EN0
VPP1
VPP2
10k
+
1µF
VCC1
VCC2
AN60 • F02
GND
Figure 2. Typical LTC1472 Application with the LT1301
3.3V/5V Boost Regulator
SafeSlot is a trademark of Linear Technology Corporation
AN60-3
Application Note 60
LTC1470 VCC Protected Switch Matrix with the LT1312
VPP Linear Regulator
Another approach is to use a linear regulator for VPP
voltages with a protected VCC switch. The LTC1470 is a
complete VCC switch matrix. The part is fully integrated with
no need for external switching FETs. Performance specifications are the same as the VCC section of the LTC1472
described above. The LTC1470 is available in the space
saving 8-pin SOIC package with a dual version, the LTC1471
in a 16-pin narrow SOIC. The LT1312 is a programmable
output voltage linear regulator designed specifically for
PCMCIA VPP drive applications. The LT1312 takes a raw,
unregulated 13V to 20V input supply and produces a clean,
regulated, selectable output voltage in conformance with
the PCMCIA standard. It comes in an 8-pin SOIC with a dual
version, the LT1313 in a 16-pin narrow SOIC.
VS
VCC SENSE
+
4V
–
EN0
EN1
The LT1312’s VPP pins are programmable to provide either
0V, 3.3V, 5V, 12V or a high impedance state. Figure 3 shows
the basic block diagram of the LT1312. Two enable inputs
(EN0 and EN1) and the VCC Sense inputs select these five
states. The logic inputs interface directly with logic high and
logic low industry standard controllers. When a VCC voltage
is selected, a comparator in the LT1312 automatically
switches the VPPOUT pin to 5V or 3.3V depending on the
voltage present at the Sense pin. The LT1312 has a 200mA
nominal output current capability with a 250mA shortcircuit current limit and thermal shutdown. These protection features can be very important when considering the
overall reliability and robustness of the main system. As
shown in Figure 4, the rise time of the LT1312 is sufficiently
slow to avoid ringing and overshoot. An additional feature
of the LT1312 is its low 25µA quiescent current in 0V or high
impedance modes.
VPPOUT
5V/DIV
The LTC1472 does not require a continuous 12V supply.
The device has on-chip charge pumps, running from the 5V
supply for driving the switches. For this reason the LT1301
is in shutdown mode, consuming only 10µA, most of the
time. The LT1301 becomes operational only when the
controller programs the LTC1472 to deliver 12V to the VPP
pin. The LTC1472 also conserves power by going to a low
1µA standby mode when both VCC and VPP outputs are
switched off. The schematic in Figure 2 includes a 10k pulldown resistor on the VCC(OUT) pin. This resistor will ensure
that when switching the VCC voltage from 5V to the off state,
the voltage will not float at 5V. The current PCMCIA specification requires the voltage be pulled down to 0.8V within
300ms when turned off. This pull-down resistor is adequate
to ensure proper operation.
VALID
EN0
Figure 4. LT1312 VPP Switching Waveform
VPPOUT
LOW DROPOUT
LINEAR
REGULATOR
VOLTAGE
CONTROL
LOGIC
AN60 • F04
20µs/DIV
+
11V
VALID
–
AN60 • F03
Figure 3. LT1312 Block Diagram
AN60-4
Application Note 60
Like the LTC1472, the LTC1470 also features SafeSlot
protection. The switches are break-before-make type with
controlled rise and fall times for minimal system power
supply impact. The built-in SafeSlot current limiting and
thermal shutdown features are vital to ensuring a robust
and reliable system. The LTC1470 also does not require a
continuous 12V supply. The device has on-chip charge
pumps running from the 5V supply for driving the switches.
51k
13V TO 20V
VLOGIC
VCC
Auxiliary Winding Power Supplies for Use
with the LT1312
VS
A_VPP_ PGM
EN0
A_VPP_ VCC
EN1
A_VPP_ VALID
VPPOUT
VPP1
+
LT1312
5V
3.3V
5VIN
3VIN
Because the LT1312 provides excellent output regulation,
the input voltage may come from a loosely regulated
source. One convenient and economic source of power is
an auxiliary winding on the main 3.3V or 5V switching
regulator inductor of the system power supply.
VPP2 PCMCIA
CARD
VCC1 SOCKET
1µF
VALID SENSE
GND
PCMCIA
CONTROLLER
VCC2
LTC1142 or LTC1148-5 Auxiliary Winding
Power Supply
LTC1470
A_VCC_ 3
EN0
A_VCC_ 5
EN1
OUT
10k
+
1µF
GND
AN60 • F05
Figure 5. Typical LTC1470 Application with the
LT1312 VPP Driver/Regulator
VIN
6.5V TO 14.5V
VIN
PDRIVE
Figure 5 shows a typical LTC1470 application with the
LT1312 used to control the VPP section. If your application
does not require VPP switching, the LT1312 is eliminated.
The LTC1470 conserves power by going to a low 1µA
standby mode when the output is switched off. The schematic in Figure 5 includes a 10k pull-down resistor on the
VCC(OUT) pin to guarantee that the VCC voltage will not float
when turned off.
+
An auxiliary winding to the 5V inductor of an LTC1142 or
LTC1148-5 based 5V power supply creates a loosely
regulated 14V power supply as shown in Figure 6. Diode
D2 rectifies the 9V output from this additional winding
adding it to the main 5V output. (Note the phasing of the
auxiliary winding shown in Figure 6.)
D1
MBRS130LT3
C1
22µF
+
C2
22µF
R4
22Ω
C4
1000pF
Q1
14V AULILIARY SUPPLY
LTC1148-5
OR
NDRIVE
1/2 LTC1142
(5V REG)
D3
MBRS140 •
R1
100Ω
Q2
SENSE +
C3
1000pF
SENSE
–
R5
0.033Ω
R2
100Ω
R3
18k
D2
T1
30µH MBRS130LT3
• 1.8T
+
C6
220µF
+
C5
22µF
EN0
EN1
+
5V
OUTPUT
TO SOCKET VPP PIN
0V, VCC, 12V OR Hi-Z
VS
VPPOUT
LT1312
VALID
+
1µF
SENSE
GND
C7
220µF
Q3
2N7002
FROM
SOCKET VCC PINS
EN0
EN1
VALID
AN60 • F06
C1, C2: AVX TPSD226M025R0200
C5: AVX TPSD226M025R0200
C6, C7: AVX TPSE227M010R0100
Q1: SILICONIX Si9430DY
Q2: SILICONIX Si9410DY
T1: DALE LPE-6582-A026 (605) 665-9301
Figure 6. Deriving 14V Power from a 5V Auxiliary Winding
AN60-5
Application Note 60
Referencing the auxiliary winding to the main 5V output
provides DC current feedback from the auxiliary supply to
the main 5V section. Returning the lead of C5 to the 5V
output as shown improves the AC transient response.
A TTL logic high on the enable line (EN0) activates the 12V
output. This will force the 5V section of the LTC1142 (or
LTC1148-5) into the continuous mode of operation. A
resistor divider, composed of R2, R3 and switch Q3 forces
an offset to counteract the internal offset at the –Sense input
of the part. Burst ModeTM operation ceases when this
external offset cancels the device’s built-in 25mV offset
forcing the switching regulator into continuous mode operation. (See the LTC1142 and LTC1148 data sheets for
further detail.) In this mode, the LT1312’s output can be
loaded without regard to the 5V output load.
Only when the LT1312 delivers 12V is the continuous
operation mode invoked. The LT1312’s input power comes
directly from the main power source (battery pack) through
diode D1 when delivering 0V, 3.3V or 5V. Again, the LT1312
output can be loaded without regard to loading on the 5V
output of the regulator. For cases of fixed VCC voltage (i.e.,
VCC = 5V only), grounding the Sense pin of the LT1312
automatically selects 5V in the VCC mode.
Figure 7 is a graph of the output voltage versus output
current for the auxiliary 14V supply shown in Figure 6.
Note that the auxiliary supply voltage is higher when the 5V
AUXILIARY OUTPUT VOLTAGE (V)
17
16
IOUT5V = 1A
14
LTC1142 or LTC1148-3.3 Auxiliary Power for Low Input
Voltage Applications
For low-battery count applications (< 6.5V) it is necessary
to modify the circuit of Figure 6. As the input voltage falls,
the 5V duty cycle increases to the point where there is
simply not enough time to transfer energy from the 5V
primary winding to the auxiliary secondary winding. For
applications where heavy 12V load currents exist in conjunction with these low input voltages, the auxiliary winding can be derived from the LTC1142’s 3.3V section or
from an LTC1148-3.3 part. The 3.3V duty cycle is more
than adequate to support 12V currents. Figure 8 shows
this circuit. In this case a transformer with a turns ratio of
1:3.6 replaces the 3.3V section inductor. In the previous
circuit, power is drawn directly from the batteries through
D1, when the switching regulator (LTC1142 or LTC11485) is in Burst Mode operation and the VPP pins require
3.3V or 5V. For these lower input voltages this technique
is invalid as the input will fall below the LT1312 linear
regulator’s dropout voltage. To correct for this situation,
the switch Q3 forces the switching regulator into continuous mode operation whenever 3.3V, 5V or 12V is selected.
Equipment with Existing 5V or 12V Supplies
The previous circuits were solutions for portable equipment that require multiple supplies from battery power.
For line-powered equipment or products that already have
5V available, the designer need only to generate a rough
supply to utilize the LT1312. Figure 9 shows how to use the
LT1172 as a boost regulator to convert the 5V input to
13.75V for use by the LT1312.
VIN = 8V
EN0 = HIGH
15
output loading is heavier. This is due to the increased
energy flowing through the main 5V inductor.
IOUT5V = 0mA
13
12
11
0.1
1
10
100
1000
AUXILIARY OUTPUT CURRENT (mA)
AN60 • F07
Figure 7. Auxiliary Winding Output Voltage vs Current
AN60-6
Some equipment such as PCs will have an existing 12V
supply. More often than not this supply is noisy and not
well regulated to the 12V ±5% flash memory specification.
Figure 10 shows a solution utilizing the LT1111 boost
regulator to deliver a 13.75V for input to the LT1312.
Burst Mode is a trademark of Linear Technology Corporation
Application Note 60
VIN
5.2V TO 18V
VIN
+
+
C1
22µF
C2
22µF
Q1
PDRIVE
C4
1000pF
R4
22Ω
D2
MBRS140
14V AUXILLARY SUPPLY
LTC1148-3.3
OR
NDRIVE
1/2 LTC1142
(3.3V REG)
D1
MBRS140
R1
100Ω
Q2
SENSE +
C3
1000pF
T1
22µH
• 3.38T
+
R3
18k
18V
+
C5
22µF
R5
0.033Ω
R2
100Ω
SENSE –
HC86
•
EN0
VS
VPPOUT
LT1312
TO SOCKET VPP PIN
0V, VCC,
12V OR Hi-Z
+
1µF
EN1
3.3V
OUTPUT
+
C6
100µF
VALID
SENSE
GND
C7
100µF
FROM
SOCKET VCC PINS
Q3
2N7002
EN0
EN1
VALID
AN60 • F08
C1, C2: AVX TPSD226M025R0200
C5: AVX TPSD226M025R0200
C6, C7: AVX TPSD107M010R0100
Q1: SILICONIX
Si9430DY
Q2: SILICONIX Si9410DY
T1: DALE LPE-6582-A086 (605) 665-9301
Figure 8. Deriving 14V Power from a 3.3V Auxiliary Winding
L1
100µH
MBRS130LT3
13.75V
5V
+
+
5
VIN
C1
47µF
VSW
EN0
10k
1%
LT1172
FB
VC
GND
3
C2
68µF
4
2
VS
VPPOUT
LT1312
VALID
1
1µF
EN1
1k
1%
TO SOCKET VPP PIN
0V, VCC, 12V OR Hi-Z
+
FROM SOCKET
VCC PINS
SENSE
GND
AN60 • F09
1k
+
C1: AVX TPSD476M016R0150
C2: AVX TPSE686M020R0150
L1: COILTRONICS CTX100-2
1µF
Figure 9. Local 5V to 13.75V Boost Regulator for Use with the LT1312
L1
100µH
MBRS130LT3
13.75V
12V
+
C1
22µF
1
+
2
VIN
100Ω
ILIM
SW1
3
C1: AVX TPSD226M025R0200
C2: AVX TPSE686M020R0150
L1: COILTRONICS CTX100-2
GND
5
SENSE
SW2
4
VS
EN0
10k
1%
LT1111CS8
C2
68µF
8
EN1
VPPOUT
LT1312
VALID
10k
1%
TO SOCKET VPP PIN
0V, VCC, 12V OR Hi-Z
+
1µF
FROM SOCKET
VCC PINS
SENSE
GND
AN60 • F10
Figure 10. Local 12V to 13.75V Boost Regulator for Use with the LT1312
AN60-7
Application Note 60
Dual Socket Design with the LTC1471 and LT1313
LTC1314: VCC Switch Driver and VPP Switch Matrix
For applications requiring two PC card sockets the designer can use the dual versions of the LTC1470 and the
LT1312. The LTC1471 dual VCC switch matrix has the
same performance characteristics as the LTC1470 and
comes in the narrow body 16-pin SOIC. The LT1313 dual
VPP regulator driver shares the same performance characteristics as the single version, the LT1312, and is also
packaged in the narrow body 16-pin SOIC. Figure 11
shows a typical two-socket application using the LTC1471
for VCC switching and the LT1313 regulating an overwinding to derive the VPP voltages. Performance is the same as
if the single version were used but with some board space
and cost savings realized.
Figure 12 shows another approach that is very space and
power efficient. Here the LTC1314 PCMCIA switch matrix,
used in conjunction with the LT1301 DC/DC converter,
provides complete power management for a PCMCIA
card socket. The LTC1314 and LT1301 combination
provide a highly efficient, minimal parts count solution.
This circuit is especially good for designers who are
adding a PCMCIA socket to existing systems that currently have only 5V or 3.3V available. Table 1 shows the
truth table for the LTC1314. The LTC1314’s logic interface allows direct connection to active high VCC or active
low VCC type controllers eliminating the need for additional glue logic.
D1
MBRS130LT3
VIN
6.5V TO 18V
VIN
+
C1
22µF
+
C2
22µF
R4
22Ω
C4
1000pF
Q1
PDRIVE
14V AUXILIARY SUPPLY
LTC1148-5
OR
NDRIVE
1/2 LTC1142
(5V REG)
D3
MBRS140 •
R1
100Ω
Q2
SENSE +
C3
R2
1000pF 100Ω
SENSE –
R3
18k
VLOGIC
Q3
2N7002
+
D2
T1
30µH MBRS130LT3
• 1.8T
+
R5
0.033Ω
C6
220µF
C5
22µF
VS
AEN0
VS
VPPOUT
1µF
AEN1
+
5V
OUTPUT
C7
220µF
Q4
2N7002
AVALID
ASENSE
LT1313
BEN0 BVPPOUT
FROM “A”
SOCKET VCC PINS
TO “B” SOCKET
VPP PINS
+
1µF
BEN1
51k
TO “A” SOCKET
VPP PINS
+
BVALID
A_VPP_PGM
A_VPP_VCC
FROM “B”
SOCKET VCC PINS
BSENSE
B_VPP_PGM
GND
GND
5V
3.3V
B_VPP_VCC
VPP_VALID
5VIN
PCMCIA
CONTROLLER
3VIN
AOUT
A_VCC_3
LTC1471
AENO
A_VCC_5
AEN1
B_VCC_3
BEN0
B_VCC_5
BEN1
C1, C2: AVX TPSD226M025R0200
C5: AVX TPSD226M025R0200
C6, C7: AVX TPSE227M010R0100
Q1: SILICONIX Si9430DY
Q2: SILICONIX Si9410DY
T1: DALE LPE-6582-A026 (605) 665-9301
Figure 11. Typical Two-Socket Application with the LTC1471 and LT1313
AN60-8
+
10k
BOUT
1µF
+
10k
TO “A” SOCKET
VCC PINS
TO “B” SOCKET
VCC PINS
1µF
AN60 • F11
Application Note 60
D1
MBRS130LT3
L1
22µH
VIN
SELECT
+ C1
33µF
SHDN
ILIM
PGND
GND
NC
VPPIN
SHDN
VDD
VPPOUT
LTC1314
PCMCIA
CARD SLOT
CONTROLLER
+ C2
LT1301
47µF
5V
12V
OUTPUT
SW
SENSE
EN0
VPP1
5V
100k
0.1µF
1k
1/2Si9956DY
DRV5
EN1
PCMCIA
CARD SLOT
0.1µF
VCC3
VCC(IN)
100k
VCC5
1k
DRV3
Si9956DY
VPP2
10k
VCC1
+
10µF
VCC2
0.1µF
GND
AN60 • F12
Si9956DY
C1: AVX TPSD476M016R0150
C2: AVX TPSD336M020R0200
L1: SUMIDA CD75-220K (708) 956-0666
3.3V
Figure 12. LTC1314 and LT1301 Configuration
Table 1. LTC1314 Truth Table
X = Don’t care.
The 3.3V VCC switch must use two MOSFETs due to the
parasitic body diode of the MOSFET. The on resistance of
the 3.3V channel is still below 0.18Ω, adequate for any
realistic current level. Different MOSFETs can be used for
lower resistance. To limit the inrush current when charging capacitive loads, an RC network is inserted between
the LTC1314 and the MOSFET’s gate. This will slow the
rise time down to a couple of milliseconds. Inrush current
is limited only by slowing down the rise time. With a 150µF
input capacitor and the 2ms rise time, the inrush current
is limited to just 275mA.
The LTC1314 drives three N-channel MOSFETs that provide VCC pin power switching. On-chip charge pumps
provide the necessary voltage to fully enhance the switches.
With the charge pumps on-chip the MOSFET drive is
available without the need for a 12V supply. This method
of VCC switching allows the use of fully enhanced
N-channel MOSFETs for low on resistance and low cost.
The LTC1314 provides a natural break-before-make action and smooth transitions due to the asymmetrical turnon and turn-off of the MOSFETs.
The VPP switching is accomplished by a combination of
the LTC1314 and LT1301 DC/DC converter. The LT1301
DC/DC converter is in shutdown mode, consuming only
10µA, to conserve power until the VPP pins require 12V.
When VPP pins require 12V, the LT1301 is activated and
the LTC1314’s internal switches will route the VPPIN pin to
the VPPOUT pin. The LT1301 is capable of delivering 12V
at 120mA maintaining high efficiency as shown in Figure
13. As shown in Figure 14, the LTC1314’s break-beforemake and slope-controlled switching will ensure that the
EN0
EN1
VCC3
VCC5
VPPOUT
DRV3
DRV5
0
0
X
X
GND
X
X
0
1
X
X
VCC(IN)
X
X
1
0
X
X
VPPIN
X
X
1
1
X
X
Hi-Z
X
X
X
X
1
0
X
1
0
X
X
0
1
X
0
1
X
X
0
0
X
0
0
X
X
1
1
X
0
0
AN60-9
Application Note 60
devices. When using a general purpose 12V supply,
make certain that you meet these criteria to ensure a safe,
robust system.
90
88
VIN = 5V
EFFICIENCY (%)
86
VIN = 3.3V
84
The major characteristics of the previous designs that are
missing are current limiting and thermal shutdown. The
low cost approach does not have these features and is
susceptible to short-circuit connections at the pins and
excessive inrush current if extremely large capacitive
loads are experienced. This may be acceptable in some
systems if the main supply is carefully current limited to
maintain operation or if some other form of protection is
added. Care should be exercised when allowing exposed
external pin connections to go without short-circuit
protection.
82
80
78
76
74
1
10
LOAD CURRENT (mA)
100 200
AN60 • F13
Figure 13. 12V Efficiency of LT1301
The LTC1314 with Higher Voltage Supplies Available
5V/DIV
VPPOUT
EN0
10µs/DIV
AN60 • F14
Figure 14. LTC1314/LT1301 VPP Switching Waveform
output voltage transition will be smooth, of moderate
slope, and without overshoot. This is critical for flash
memory products to prevent damaging parts from overshoot and ringing exceeding the 14V part limit.
The LTC1314’s VPPIN pin may be connected directly to a
stable 12V supply. However, this should be done with
caution. The 12V supply available with most computer
systems has an excessive voltage tolerance and is accompanied by significant digital switching noise. The
specification for flash memory requires 12V ±5%. Voltages greater than 14V will result in damaged memory
AN60-10
Often systems have an available supply voltage greater
than 12V. The LTC1314 can be used in conjunction with
the LT1121 linear regulator to supply the PC card socket
with all necessary voltages. Figure 15 shows this circuit.
The LTC1314 will enable the LT1121 linear regulator only
when 12V is required at the VPP pin. In all other modes the
LT1121 is in shutdown mode and consumes only 16µA.
This LT1121 also provides thermal and current limiting
features to increase the robustness of the socket. This
configuration can be used in conjunction with the LTC1142
auxiliary winding techniques shown earlier to provide a
current limited, protected solution.
LTC1315 Dual Switch Driver and VPP Switch Matrix
For applications requiring two PC card sockets the LTC1315
provides a single package switch matrix solution. The
LTC1315 is a dual version of the LTC1314 with two
complete “A” and “B” sections and operates in a similar
fashion. Figure 16 shows a typical circuit utilizing the
LT1301 to derive 12V from the 5V line. For maximum
efficiency, the ASHDN and BSHDN signals are diode OR’d
to enable the LT1301 only when 12V VPP is required.
Application Note 60
VIN
13V TO 20V
IN
+
10µF
OUT
200pF
LT1121CS8
SHDN
ADJ
GND
100k
5V
121k
56.2k
VPPIN
VDD
SHDN
2N7002
VPPOUT
LTC1314
EN0
PCMCIA
CARD SLOT
CONTROLLER
+
1µF
SOLID
TANTALUM
VPP1
5V
100k
0.1µF
1k
VPP2
1/2 Si9956DY
DRV5
EN1
PCMCIA
CARD SLOT
0.1µF
VCC3
VCC(IN)
100k
VCC5
1k
DRV3
Si9956DY
10k
VCC1
+
10µF
VCC2
0.1µF
GND
AN60 • F15
Si9956DY
3.3V
Figure 15. LTC1314 with the LT1121 Linear Regulator
L1
22µH
+ C1
VCC
47µF
+ C2
SW
33µF
SELECT
SENSE
LT1301
SHDN
ILIM
5V
PGND
100k
1N4148
D1
MBRS130LT3
NC
GND
C1: AVX TPSD476M016R0150
C2: AVX TPSD336M020R0200
L1: SUMIDA CD75-220K (708) 956-0666
VDD
ASHDN AVPPIN
BSHDN BVPPIN
AVPPOUT
1k
ADRV5
0.1µF
LTC1315
Q1A
1/2 Si9956DY
0.1µF
100k
Q2A
Si9956DY
10k
AVCC1
VCC1
+
1k
ADRV3
0.1µF
AVCC0
VPP2
PC CARD
SOCKET 1
AVCC(IN)
AEN0
AEN1
PCMCIA
CONTROLLER
VPP1
5V
100k
10µF
VCC2
Q2B
Si9956DY
VCC(IN)
BEN0
3.3V
BEN1
BVPPOUT
BVCC0
BVCC1
VPP1
5V
100k
1k
BDRV5
0.1µF
Q1B
1/2 Si9956DY
0.1µF
Q3A
Si9956DY
10k
PC CARD
SOCKET 2
BVCC(IN)
100k
VPP2
VCC1
+
1k
BDRV3
0.1µF
10µF
Q3B
Si9956DY
GND
VCC2
AN60 • F16
3.3V
Figure 16. Typical Two-Socket Application Using the LT1315 and the LT1301
AN60-11
Application Note 60
THE OTHER SIDE OF THE FENCE: PC CARD ON-CARD
POWER MANAGEMENT
Designers of PC cards may want to have greater control of
the power management and not be at the mercy of the
socket’s provisions. Many sockets do not support all of the
voltages that the PCMCIA standard outlines or may not be
able to meet the card’s current demands. In addition, not
all PCMCIA sockets will incorporate smooth voltage transitions thus damaging PC cards. To assure maximum
reliability and broad compatibility, the PC card designer
can design the card for VCC only operation. With the
release of the new PCMCIA low voltage card specifications, cards requiring only 3.3V will become popular. This
will often necessitate on-card 3.3V to 5V conversion and
VPP generation.
(350µA). The LT1106 also produces a VPP valid signal
when the voltage at the AVPP pin is greater than 11.5V to
indicate that a valid programming voltage is available. An
additional comparator output indicates whether the VCC
supply is 3.3V or 5V. The LT1106 is also selectable to
produce 5V or 12V and has a shutdown pin to reduce
supply current to only 10µA. The Soft Start pin controls the
rise time of the output by a single resistor and capacitor.
The LT1106 combines an efficient switching regulator
with many special PCMCIA interface features. On-chip
comparators sense the socket VPP pins. If 12V is present,
internal drivers enhance the P-channel MOSFET switches,
Q1 and Q2, and the LT1106 goes into a low power mode
AN60-12
D
0.1µF
BSS84
S
VPP2
0.1µF
D
BSS84
S
POWER ON
VCC
VPP1
G1
SW
AVPP
1µF
LT1106
VPP2
G2
12V
60mA
VPP VALID
VPP
VALID
3/5 DETECT
3/5
SOFT START
ON/OFF
PGND GND
12/5
1M
0.1µF
AN60 • F17
CIN: TANTALUM
FOR TYPE I CARDS (1.19mm MAX HEIGHT)
L1: COILTRONICS CTX02-11238 (407) 241-7876
OR DALE ILS-2538-10 (605) 665-9301
D1: PHILIPS BAT54C (4 IN PARALLEL)
FOR TYPE II CARDS (2.2mm MAX HEIGHT)
L1: MURATA ERIE LQH3C100K04M00
D1: PHILIPS PRLL5818 OR MOTOROLA MBR0530
LT1106: PC Card 3.3V/5V to 12V Converter for
Flash Memory
Figure 17. Typical LT1106 Application
AVPP
5V/DIV
Flash memory cards are a typical Type I and Type II PC card
application. The PC card socket should provide the necessary VPP 12V programming voltage. Card designers often
prefer to have this critical voltage under their own control.
The LT1106 is a switching regulator in the ultra-thin 20 pin
TSSOP package designed specifically for use in PC cards.
Figure 17 shows a typical application of the LT1106 as a
boost regulator from 3.3V or 5V to 12V at 60mA.
D1
1µF
VPP1
The size constraints of PC cards make on-card power
management design extremely challenging. Board “Real
Estate” problems are further compounded by severe height
requirements. There are few components available compatible with the Type I card’s 1.19mm height requirement.
Type II cards are only marginally easier at 1.752mm height
for center mounted cards and 2.31mm for offset mounted
cards. These dimensions are for typical applications and
vary depending on board thickness and card frame.
L1
10µH
CIN
VCC
3.3V/5V
VPPVAL
ON/OFF
50µs/DIV
AN60 • F18
Figure 18. LT1106 VPP Switching Waveform
Application Note 60
Important performance features, in addition to the thin
TSSOP package of the LT1106, make the part ideal for PC
card applications. The 500kHz switching frequency allows
the use of a small value, small size inductor. Small inductors in an ultra-thin form factor, critical for Type I and Type
II PC card applications are achievable. The LT1106 has
been designed to require only 1µF input and output capacitance. The LT1106 also features Burst Mode operation
with efficiency as high as 85% to minimize battery drain
and any on-card thermal issues.
Inductor, diode, and capacitor selection are critical to
achieving good regulation and high efficiency at the output
currents desired. The LT1106 circuit (Figure 17) requires
a 10µH inductor. This inductor must not saturate at the
LT1106’s rated current, must have low DC resistance, and
its inductance as a function of frequency must be relatively
constant up to the 500kHz oscillator frequency. The combination of characteristics makes the inductor design
formidable. There are several acceptable inductors listed
in Figure 17.
The diode selection criteria are also difficult to meet. The
diode must switch quickly, have low leakage and have a low
forward voltage drop. The switching speed requirement is
due primarily to the LT1106’s 500kHz oscillator and the low
forward voltage drop of the part is necessary to achieve
good efficiency. At the time of this writing there is no diode
that will satisfy this requirement in a package less than
1.19mm in height necessary for Type I cards. There are
several SOT-23 packaged, fast switching diodes that can be
paralleled to share the current requirements and therefore
run at a lower forward voltage drop. The BAT54C Schottky
diode from Philips is a dual diode in the SOT-23 package
that is a solution to this problem. The circuit in Figure 17
uses four of these packages (eight diodes) in parallel to get
the forward voltage drop down to 530mV at 600mA.
Capacitor selection is also critical. The capacitors must be
sufficient in value with an ESR below 0.5Ω to assure good
efficiency and output ripple values. The small 1µF output
capacitor value allows the use of ceramic capacitors. Thin
surface mount ceramic capacitors are readily available.
Paralleling ten 0.1µF capacitors, often used to decouple
ICs, yields a cost effective solution.
Figure 19 shows the efficiency of the LT1106 when producing 12V at various current levels. You can see how the
selection of the passive components affects the efficiency
of the regulator. The dashed lines represent the 12V converter made with the ultra-thin Type I card components and
shows good efficiency above 80% for most current ranges.
The larger Type II components allow the same circuit
topology to produce 2% to 3% better efficiency.
86
TYPE I CARDS
TYPE II CARDS
84
82
EFFICIENCY (%)
In Figure 18 the output voltage transition is smooth with
no overshoot and ringing. This type of response assures
the reliability of flash memory products.
VIN = 5V
VIN = 5V
80
VIN = 3.3V
78
VIN = 3.3V
76
74
72
70
1
10
LOAD CURRENT (mA)
100
DN60 • F19
Figure 19. 12V Output Efficiency
LT1106 3.3V to 5V DC/DC Converter for Type I Cards
The LT1106 has an output voltage select pin for 12V output
or 5V output. Connecting this pin to the 3.3V input will
program the LT1106 for 5V output. Utilizing the same
components as the 12V output design, this circuit will
provide 5V at up to 120mA output current. For maximum
efficiency, the ON/OFF control allows the device to be
activated only when required. Figure 20 shows a typical
AN60-13
Application Note 60
application. The LT1106’s higher frequency operation allows for smaller components making it an ideal part for oncard DC/DC regulation. The typical efficiency is plotted in
Figure 21.
L1
10µH
D1
5V
120mA
3.3V
1µF
POWER
ON
VCC
NC
VPP1
NC
G1
NC
VPP2
NC
G2
1µF
SW
AVPP
LT1106
VPP VALID
NC
3/5 DETECT
NC
cally for high frequency, small component operation. For
this reason the inductor and capacitor values will not be as
small as the LT1106 design. The LT1300’s SOIC package
and the use of a larger inductor with tantalum capacitors
limit this design to Type II or Type III cards. Figure 22 shows
a typical circuit utilizing the LT1300 to deliver 5V at 250mA
from a 3.3V input. While the passive devices are not as thin
as those used with the LT1106, the parts specified are much
thinner than those used in conventional designs with a
more standard height requirement. Figure 23 shows the
typical efficiency of this design.
ON/OFF SOFT START
PGND GND
12/5
1M
L1
10µH
0.1µF
3.3V
DN60 • F20
+ C1
FOR TYPE I CARDS (1.19mm MAX HEIGHT)
L1: COILTRONICS CTX02-11238 (407) 241-7876
OR DALE ILS-2538-10 (605) 665-9310
D1: PHILIPS 4 BAT54s IN PARALLEL
68µF
D1
VCC
SW
SELECT
SENSE
+ C2
5V
250mA
68µF
LT1300
Figure 20. LT1106 3.3V to 5V DC/DC Converter
SHDN
PGND
NC
ILIM
GND
76
DN60 • F22
C1, C2: SPRAGUE 592D686X0010R2T, 68µF, 10V, (1.5mm MAX HEIGHT)
D1: MOTOROLA MBR0530 (1.35mm MAX HEIGHT)
L1: MURATA ERIE LQH3C220K04, 22µH, 2 IN PARALLEL (2.2mm MAX HEIGHT) OR
SUMIDA CLS62-100L, 10µH, (2.5mm MAX HEIGHT)
74
EFFICIENCY (%)
72
70
Figure 22. LT1300 3.3V to 5V Converter
for Type II or Type III Cards
68
66
64
84
62
82
SUMIDA
60
10
100
LOAD CURRENT (mA)
1000
AN60 • F21
Figure 21. LT1106 3.3V to 5V Efficiency
EFFICIENCY (%)
1
80
78
MURATA
76
74
LT1300 3.3V to 5V DC/DC Converter for Type II Cards
72
For PC cards requiring 3.3V to 5V conversion at more than
120mA, a design utilizing the LT1300 can provide a solution
for Type II and Type III cards. While the LT1300 can deliver
more current than the LT1106, it was not designed specifi-
70
AN60-14
1
10
100
CURRENT LOAD (mA)
300
AN60 • F23
Figure 23. LT1300 3.3V to 5V Efficiency
Application Note 60
CONCLUSION
PCMCIA expansion sockets are becoming more popular
with portable equipment. The expansion sockets are also
being used in desktop systems and other systems that
require easy expandability. The PCMCIA specification gives
a set of guidelines that form a good starting point for the
design of any portable system. There are a host of other
practical design issues to consider for a robust system. The
main issues are switch on-resistance, inrush current, shortcircuit protection and switch output ringing during switching. The main features to look for in the switch matrix are
easy interface to standard controllers, low enough on-
resistance, slowed switch rise times, and current limiting
and thermal shutdown. By designing with these features
the PCMCIA socket will meet the voltage requirements of all
cards and will ensure a reliable system with a satisfied
customer.
On-card power management can take many forms. Conversion from 3.3V or 5V to other voltages, both positive
negative, can be achieved through careful design and
component selection. The specific voltage requirements
will be as varied as the wide diversity of PC card products
themselves. For solutions to your specific needs, call Linear
Technology for applications assistance.
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.
AN60-15
Application Note 60
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Linear Technology Corporation
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Phone: (215) 638-9667
FAX: (215) 638-9764
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FAX: (508) 658-2701
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Linear Technology Corporation
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Phone: (408) 432-1900
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0195
AN60-16
Linear Technology Corporation
LT/GP 0195 10K • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7487
(408) 432-1900 ● FAX: (408) 434-0507 ● TELEX: 499-3977
 LINEAR TECHNOLOGY CORPORATION 1995