8
LTC1314/LTC1315
APPLICATIONS INFORMATION
WUU
U
+
V
DD
1µF
VPP
IN
SHDN
Q1A
1/2 Si9956DY
Si9956DY
Q2A
Q2B
VPP
OUT
VPP1
VPP2
V
CC
1314/15 F03
LTC1314
PCMCIA
CONTROLLER
EN0
EN1
GNDPGND
V
OUT
2N7002
13V TO 20V
(MAY BE FROM
AUXILLARY
WINDING)
V
IN
200pF
121k
1%
56.2k
1%
LT1121
SHDN
5V
5V
ADJ
V
CC0
V
CC1
DRV5
V
CCIN
DRV3
GND
5V
3.3V
PC CARD
SOCKET
+
1µF
0.1µF
+
10µF
100k
the asymmetrical turn-on and turn-off of the MOSFETs.
The LT1301 switching regulator is in shutdown mode and
consumes only 10µA until the VPP pins require 12V.
The VPP switching is accomplished by a combination of
the LTC1314/LTC1315 and LT1301. The LT1301 is in
shutdown mode to conserve power until the VPP pins
require 12V. When the VPP pins require 12V, the LT1301
is activated and the LTC1314/LTC1315’s internal switches
route the VPP
IN
pin to the VPP
OUT
pin. The LT1301 is
capable of delivering 12V at 120mA maintaining high
efficiency. The LTC1314/LTC1315’s break-before-make
and slope-controlled switching will ensure that the output
voltage transition will be smooth, of moderate slope, and
without overshoot. This is critical for flash memory prod-
ucts to prevent damaging parts from overshoot and
ringing exceeding the 13.5V device limit.
With Higher Voltage Supplies Available
Often systems have an available supply voltage greater
than 12V. The LTC1314/LTC1315 can be used in conjunc-
tion with an LT1121 linear regulator to supply the PC card
socket with all necessary voltages. Figures 3 and 4 show
these circuits. The LTC1314/LTC1315 enable the LT1121
linear regulator only when 12V is required at the VPP pins.
In all other modes the LT1121 is in shutdown mode and
consumes only 16µA. The LT1121 also provides thermal
shutdown and current limiting features to protect the
socket, the card and the system regulator.
Supply Bypassing
For best results, bypass V
CCIN
and VPP
IN
at their inputs
with 1µF capacitors. VPP
OUT
should have a 0.01µF to 0.1µF
capacitor for noise reduction and electrostatic discharge
(ESD) damage prevention. Larger values of output capaci-
tor will create large current spikes during transitions,
requiring larger bypass capacitors on the V
CCIN
and VPP
IN
pins.
Figure 3. LTC1314 with the LT1121 Linear Regulator
