LT1309 Linear Technology, LT1309 Datasheet - Page 4

• Manufacturer Part Number: LT1309
• Description: 500kHz Micropower DC/DC Converter for Flash Memory
• Manufacturer: Linear Technology

PI FU CTIO S
LT1309
SOFT START (Pin 1): A 0.1 F/1M parallel RC from this
pin to GND provides a Soft Start function upon device
turn-on. Initially about 80 A will flow from the pin into the
capacitor. When the voltage at the pin reaches approxi-
mately 0.4V, current ceases flowing out of the pin.
V
capacitance is required. More capacitance reduces ring-
ing on the supply line.
PGND (Pin 3): Power Ground. Connect to ground plane.
V
present on this pin. To minimize radiated noise keep
layout short and direct.
4
TYPICAL PERFORMANCE CHARACTERISTICS
CC
SW
U
(Pin 2): Input Supply. At least 1 F input bypass
VPP VALID
(Pin 4): Collector of Power Switch. High dV/dt
10V/DIV
10V/DIV
V
2V/DIV
ON/OFF
V
12V
OUT
U
Start-Up Waveforms, I
U
W
50 s/DIV
LOAD
U
AC COUPLED
12V OUTPUT
I
LOAD
= 1mA
1V/DIV
60mA
10mA
Load Transient Response,
C
OUT
1309 G08
= 1 F
50 s/DIV
GND (Pin 5): Signal Ground. Connect to ground plane.
VPP VALID (Pin 6): This pin provides a logic signal
indicating that output voltage has reached 12V. Active low
with internal 200k pull-up resistor.
SENSE (Pin 7): Output Sense Pin. This pin connects to a
resistive divider that sets the output voltage. In shutdown,
the resistor string is disconnected and current into this pin
reduces to < 1 A.
ON/OFF (Pin 8): Shutdown Control. When pulled below
1.5V, this pin disables the LT1309 and reduces supply
current to 9 A. All circuitry is disabled in shutdown. The
part is enabled when ON/OFF is greater than 1.5V.
500mA/DIV
10V/DIV
V
5V/DIV
ON/OFF
V
OUT
I
L
Start-Up Waveforms, I
1309 G10
50 s/DIV
LOAD
= 10mA
1309 G09