LT1309
OBSOLETE:
Contact Linear Technology for Potential Replacement
FOR INFORMATION PURPOSES ONLY
500kHz Micropower
DC/DC Converter
for Flash Memory
U
12V Output Efficiency
86
84
82
EFFICIENCY (%)
80
78
76
74
72
LT1309 • TA01
FEATURES
I
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DESCRIPTIO
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60mA Output Current at 12V from 3V or 5V Supply
Shutdown to 9µA
VPP VALID Comparator
Up to 85% Efficiency
Switching Frequency: 500kHz (Typical)
Quiescent Current: 650µA
Low V
CESAT
Switch: 300mV at 0.5A (Typical)
Soft Start Reduces Supply Current Transients
Uses Low Value, Small Size,
Surface Mount Inductors
Available in 8-Lead SO Package
The LT
®
1309 is a 500kHz micropower DC/DC converter
for Flash Memory. The regulator features Burst Mode
TM
operation with a 0.5A, 300mV switch, enabling 85%
efficiency at the fixed 12V output. High frequency opera-
tion permits the use of small value, and therefore small
size, surface mount inductors and capacitors. The LT1309
comes in an 8-lead SO package allowing extremely
compact PC board layouts. These features make the
device attractive for PCMCIA cards, cellular phones and
other applications where PC board space is limited.
Quiescent current is 650µA decreasing to 9µA when the
part shuts down. The device includes a soft start feature
which limits supply current transients during turn-on.
The LT1309 contains a VPP VALID comparator with a
logic output that goes low when the output voltage is
ready to program 12V Flash Memory. This comparator
simplifies the interface to external control logic.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a trademark of Linear Technology Corporation.
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Flash Memory VPP Generators
Type II and III PCMCIA Card DC/DC Converters
3V to 12V, 5V to 12V Converters
Portable Computers and Instruments
Cellular Telephones
DC/DC Converter Module Replacements
12V, 60mA Flash Memory Programming Supply
V
IN
3.3V TO 5V
V
IN
VPP VALID
ON/OFF
C1
4.7µF
L1*
10µH
D1
†
VPP 12V, 60mA
+
VPP VALID SENSE
LT1309
SOFT
ON/OFF
START
PGND
GND
* MURATA ERIE LQH3C100K0YM00
** CERAMIC
†
MOTOROLA MBR0530
UO
TYPICAL APPLICATI
UO
APPLICATI
S
V
IN
= 5V
V
SW
V
IN
= 3.3V
R1
1M
C3
0.1µF
C2
1µF**
70
1
10
LOAD CURRENT (mA)
100
LT1309 • TA02
1
LT1309
ABSOLUTE
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
SOFT START 1
V
CC
2
PGND 3
V
SW
4
8
7
6
5
ON/OFF
SENSE
VPP VALID
GND
V
CC
Voltage............................................................... 7V
V
SW
Voltage ............................................................ 20V
V
SENSE
Voltage ....................................................... 20V
V
ON/OFF
Voltage......................................................... 7V
V
SEL
Voltage ............................................................. 7V
I
LIM
Voltage .............................................................. 7V
Maximum Power Dissipation ............................ 500mW
Operating Temperature Range ..................... 0°C to 70°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
ORDER PART
NUMBER
LT1309CS8
S8 PART MARKING
1309
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 150°C,
θ
JA
= 150°C/W
Consult factory for Industrial and Military grade parts.
ELECTRICAL CHARACTERISTICS
SYMBOL
I
Q
PARAMETER
Quiescent Current
Quiescent Current, Shutdown
Input Voltage Range
Output Sense Voltage
Output Referred Comparator Hysteresis
f
OSC
DC
t
ON
V
CESAT
Oscillator Frequency
Maximum Duty Cycle
Switch ON Time
Reference Line Regulation
Switch Saturation Voltage
Switch Leakage Current
Switch Current Limit
Soft Start Current
ON/OFF Input Voltage Low
ON/OFF Input Voltage High
ON/OFF Bias Current
T
A
= 25°C, V
CC
= 5V, V
ON/OFF
= 3V, unless otherwise noted.
MIN
TYP
650
9
2
q
CONDITIONS
V
SENSE
= 12V
V
ON/OFF
= 0.2V
MAX
900
15
6
12.6
700
92
0.15
350
10
900
950
120
0.8
UNITS
µA
µA
V
V
mV
kHz
%
µs
%/V
mV
µA
mA
mA
µA
V
V
µA
µA
µA
µA
µA
V
V
11.5
400
12
35
500
85
1.7
0.06
230
0.1
Current Limit Not Asserted
q
80
2V < V
IN
< 6V
I
SW
= 0.5A
V
SW
= 12V, Switch Off
V
IN
= 5V, Soft Start Floating
V
IN
= 3V, Soft Start Floating
Soft Start Grounded
1.6
V
ON/OFF
= 5V
V
ON/OFF
= 3V
V
ON/OFF
= 0V
V
ON/OFF
= 0.2V
400
450
600
650
80
16.0
8.0
0.1
50.0
0.1
V
SENSE
– 200mV
0.13
4
4.5
24.0
14.0
1.0
90
1
0.3
Sense Pin Input Current
VPP VALID Threshold
VPP VALID Output Voltage Low
VPP VALID Output Voltage High
V
SENSE
Rising (High to Low Transition)
I
SINK
= 100µA
I
SOURCE
= 2.5µA
The
q
denotes specifications which apply over the full operating
temperature range.
2
U
W
U
U
W W
W
LT1309
TYPICAL PERFORMANCE CHARACTERISTICS
Oscillator Frequency
800
OSCILLATOR FREQUENCY (kHz)
1000
900
SWITCH CURRENT (mA)
800
V
CC
= 3V
700
V
CC
= 5V
600
500
400
–50
SWITCH SATURATION VOLTAGE (mV)
700
600
500
400
300
–50
–25
0
25
50
TEMPERATURE (°C)
Sense Voltage
12.20
12.15
SUPPLY CURRENT (µA)
SENSE VOLTAGE (V)
800
12.10
12.05
12.00
11.95
11.90
11.85
11.80
–50
–25
50
25
TEMPERATURE (°C)
0
75
100
1309 G04
Supply Current in Shutdown
14
12
10
8
6
4
2
0
–50
V
CC
= 3V
V
CC
= 5V
MAXIMUM DUTY CYCLE (%)
90
SUPPLY CURRENT (µA)
95
–25
50
25
0
TEMPERATURE (°C)
U W
75
1309 G01
Switch Current Limit
250
Switch Saturation Voltage
I
SW
= 500mA
225
200
175
150
125
100
–50
100
–25
0
25
50
TEMPERATURE (°C)
75
100
1309 G02
–25
0
25
50
TEMPERATURE (°C)
75
100
1309 G03
Supply Current
700
V
CC
= 5V
V
CC
= 3V
600
500
400
300
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
1309 G05
Maximum Duty Cycle
85
80
75
75
100
1309 G06
70
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
1309 G07
3
LT1309
TYPICAL PERFORMANCE CHARACTERISTICS
Start-Up Waveforms, I
LOAD
= 1mA
12V
V
OUT
2V/DIV
I
L
500mA/DIV
V
ON/OFF
10V/DIV
50µs/DIV
1309 G08
VPP VALID
10V/DIV
V
ON/OFF
10V/DIV
PI FU CTIO S
SOFT START (Pin 1):
A 0.1µF/1MΩ parallel RC from this
pin to GND provides a Soft Start function upon device
turn-on. Initially about 80µA 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
CC
(Pin 2):
Input Supply. At least 1µF input bypass
capacitance is required. More capacitance reduces ring-
ing on the supply line.
PGND (Pin 3):
Power Ground. Connect to ground plane.
V
SW
(Pin 4):
Collector of Power Switch. High dV/dt
present on this pin. To minimize radiated noise keep
layout short and direct.
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 < 1µA.
ON/OFF (Pin 8):
Shutdown Control. When pulled below
1.5V, this pin disables the LT1309 and reduces supply
current to 9µA. All circuitry is disabled in shutdown. The
part is enabled when ON/OFF is greater than 1.5V.
4
U W
Start-Up Waveforms, I
LOAD
= 10mA
V
OUT
5V/DIV
50µs/DIV
1309 G09
Load Transient Response,
C
OUT
= 1µF
12V OUTPUT
1V/DIV
AC COUPLED
60mA
10mA
I
LOAD
50µs/DIV
1309 G10
U
U
U
LT1309
BLOCK DIAGRA
W
ON/OFF
8
POWER ON
864k
V
CC
C3
36mV
V
CC
2
SENSE
7
+
+ –
200k
–
+
–
VPP VALID
Q3
1
R2
700Ω
R1
3Ω
C2
6
BIAS
SW
4
Q2
×
1
Q1
×
50
4k
OFF
C1
500kHz
OSCILLATOR
SOFT START
V
REF
1.24V
OPERATIO
The LT1309 is a current limited, Burst Mode (gated
oscillator) type switching regulator that produces a 12V
output from a 3.3V or 5V input. Operation can best be
understood by referring to the Block Diagram. When the
voltage at the Sense pin (Pin 7) is less than 12V, compara-
tor C1 enables the oscillator, turning switches Q1 and Q2
on. The switch turns off when current limit is reached or
when the oscillator maximum on-time is reached. When
+
5
GND
3
PGND
1309 BD
100k
–
U
Q2 turns off, current built up in the inductor flows into the
output capacitor and load. This action occurs until the
output voltage reaches 12V. During start-up, the Sense pin
voltage is either 3.3V or 5V, depending on the input. The
VPP VALID signal remains high until the output voltage
reaches 12V, signaling correct voltage level to program
flash memory. Connecting a 1µF/0.1µF parallel RC to the
Soft Start pin limits inrush current during start-up.
5
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