LTC1470/LTC1471
APPLICATIONS INFORMATION
TOTAL SYSTEM COST CONSIDERATIONS
The cost of an additional step-up switching regulator, induc-
tor, rectifier and capacitors to produce 12V for VPP can be
eliminated by using an auxiliary winding on either the 3.3V
or 5V output of the system switching regulator to produce an
auxiliary 15V supply for VPP power.
And, because the LTC1470/LTC1471 do not require 12V
power to operate (only 5V), the 12V VPP regulation and
switching may be operated separately from the 3.3V/5V V
CC
switching. This increases system configuration flexibility
and
reduces total system cost
by eliminating the need for a
third regulator for 12V power.
V
IN
6.5V TO 18V
V
IN
10
D1
MBRS140
+
9
Q1
C1
68µF
PDRIVE
1/2 LTC1142HV
(5V REG)
NDRIVE
20
Q2
SENSE
+
15
C2
1000pF
D3
MBRS130T3
T1*
R1
30µH
100Ω
SENSE
–
14
R3
18k
R2
100Ω
R5
0.033Ω
+
Q3
2N7002
AVPPEN0
BVPPEN0
Q4
2N7002
3.3V
0.1µF
A3V
IN
A3V
IN
B3V
IN
B3V
IN
A5V
IN
BOUT
0.1µF
B5V
IN
LTC1471
AV
CC
EN0
AV
CC
EN1
BV
CC
EN0
BV
CC
EN1
AEN0
AEN1
BEN0
BEN1
GND
GND
AOUT
AOUT
BOUT
* LPE-6562-A026 DALE (605) 665-9301
Figure 3. Cost Effective Complete SafeSlot Dual PCMCIA Power Management System
(with 15V Auxiliary Supply from LTC1142HV 5V Regulator Inductor)
8
U
W
U
U
LTC1142HV Auxiliary Winding Power Supply
Figure 3 is a schematic diagram which describes how a
loosely regulated 15V power supply is created by adding an
auxiliary winding to the 5V inductor in a split 3.3V/5V
LTC1142HV power supply system. An LT1313, dual VPP
regulator/driver with SafeSlot protection, produces “clean”
3.3V, 5V and 12V power from this loosely regulated 15V
output for the PC card slot VPP pins. (See LT1312 and
LT1313 data sheets for further detail.)
A turns ratio of 1:1.8 is used for transformer T1 to ensure that
the input voltage to the LT1313 falls between 13V and 20V
under all load conditions. The 9V output from this additional
(15V)
R4
22Ω
C4
1000pF
AVPPEN0
AVPPEN1
D2
MBRS140
AVALID
V
S
AEN0
AEN1
AVALID
V
S
AVPP
OUT
+
1µF
TO “A” SLOT
VPP PINS
1.8:1
+
LT1313
C5
22µF
BVPPEN0
BVPPEN1
5V
OUTPUT
BVALID
BEN0
BEN1
BVALID
BSENSE
GND
ASENSE
BVPP
OUT
FROM “A” V
CC
PINS
+
1µF
TO “B” SLOT
VPP PINS
C3
220µF
FROM “B” V
CC
PINS
GND
5V
+
1µF
TANT
TO “A” SLOT
V
CC
PINS
10k
+
1µF
TANT
10k
TO “B” SLOT
V
CC
PINS
1470/71 F03
LINER [ LINEAR TECHNOLOGY ]
