LTC1262
12V, 30mA Flash Memory
Programming Supply
FEATURES
s
s
s
s
s
s
s
DESCRIPTIO
Regulated 12V
±5%
Output Voltage
No Inductors
Supply Voltage Range: 4.75V to 5.5V
Guaranteed 30mA Output
Low Power: I
CC
= 500
µ
A
I
CC
in Shutdown: 0.5µA
8-Pin PDIP or SO-8 Package
The LTC
®
1262 is a regulated 12V, 30mA output DC/DC
converter. It is designed to provide the 12V
±5%
output
necessary to program byte-wide flash memories. The
output will provide up to 30mA from input voltages as low
as 4.75V without using any inductors. Only four external
capacitors are required to complete an extremely small
surface mountable circuit.
The TTL compatible shutdown pin can be directly con-
nected to a microprocessor and reduces the supply cur-
rent to less than 0.5µA. The LTC1262 offers improved
shutdown current performance and requires fewer exter-
nal components than competing solutions.
The LTC1262 is available in an 8-pin PDIP or SO-8
package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATI
s
s
s
S
12V Flash Memory Programming Supplies
Compact 12V Op Amp Supplies
Battery-Powered Systems
TYPICAL APPLICATI
1
0.22µF
2
3
0.22µF
4
C1
–
C1
+
SHDN
GND
LTC1262
V
OUT
V
CC
8
7
FROM MPU
FLASH
MEMORY
VPP
4.7µF
V
CC
LTC1262 • TA01
4.7µF
C2
–
C2
+
6
5
SHDN 5V
5V/DIV 0V
12V
V
OUT
5V/DIV 5V
0V
1ms/DIV
1262 TA01a
V
CC
4.75V TO 5.5V
U
In/Out of Shutdown
+
UO
+
UO
1
LTC1262
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
C1
–
1
C1
+
2
C2
–
3
C2
+
Supply Voltage (V
CC
) ................................................ 6V
Input Voltage (SHDN) ................... – 0.3V to V
CC
+ 0.3V
Output Current (I
OUT
) ........................................... 50mA
Operating Temperature Range
LTC1262C................................................ 0°C to 70°C
LTC1262I........................................... – 40°C to 85°C
Storage Temperature Range ................ – 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
ORDER PART
NUMBER
8
7
6
5
SHDN
GND
V
OUT
V
CC
4
LTC1262CN8
LTC1262CS8
LTC1262IS8
S8 PART MARKING
1262
1262I
N8 PACKAGE
8-LEAD PDIP
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 150°C,
θ
JA
= 100°C/W (N8)
T
JMAX
= 150°C,
θ
JA
= 150°C/W (S8)
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
V
CC
= 4.75V to 5.5V, T
A
= – 40°C to 85°C, (Notes 2, 3), unless otherwise noted.
SYMBOL
V
OUT
I
CC
I
SHDN
f
OSC
PARAMETER
Output Voltage
Supply Current
Shutdown Supply Current
Oscillator Frequency
Power Efficiency
R
SW
V
IH
V
IL
V
CC
to V
OUT
Switch Impedance
SHDN Input High Voltage
SHDN Input Low Voltage
SHDN Input Current
V
CC
= 5V, V
SHDN
= 0V, 0°C
≤
T
A
≤
70°C
V
CC
= 5V, V
SHDN
= 0V, – 40°C
≤
T
A
≤
85°C
V
CC
= 5V, V
SHDN
= 5V
C1 = C2 = 0.22µF, C
IN
= C
OUT
= 4.7µF, (Figures 1, 2)
C1 = C2 = 0.22µF, C
IN
= C
OUT
= 4.7µF, (Figures 1, 2)
CONDITIONS
0mA
≤
I
OUT
≤
30mA, V
SHDN
= 0V, 0°C
≤
T
A
≤
70°C
0mA
≤
I
OUT
≤
30mA, V
SHDN
= 0V, – 40°C
≤
T
A
≤
85°C
No Load, V
SHDN
= 0V, 0°C
≤
T
A
≤
70°C
No Load, V
SHDN
= 0V, – 40°C
≤
T
A
≤
85°C
No Load, V
SHDN
= V
CC
V
CC
= 5V, I
OUT
= 30mA
V
CC
= 5V, I
OUT
= 30mA
V
CC
= V
SHDN
= 5V, I
OUT
= 0mA
q
q
q
q
q
q
q
q
q
q
q
q
q
MIN
11.4
11.2
TYP
MAX
12.6
12.6
UNITS
V
V
mA
mA
µA
kHz
%
0.5
0.5
0.5
300
74
0.18
2.4
1.0
1.3
10
2
0.8
– 20
–35
– 10
–10
0.06
500
3.3
–5
–5
10
t
ON
t
OFF
Turn-On Time
Turn-Off Time
The
q
denotes specifications which apply over the full operating
temperature range.
Note 1:
Absolute maximum ratings are those values beyond which the life
of the device may be impaired.
Note 2:
All currents into device pins are positive; all currents out of device
pins are negative. All voltages are referenced to ground unless otherwise
specified.
Note 3:
All typicals are given at V
CC
= 5V, T
A
= 25°C.
2
U
kΩ
V
V
µA
µA
µA
µs
ms
W
U
U
W W
W
LTC1262
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency vs Output Current
85
80
75
V
CC
= 5.5V
70
65
60
55
3.6
SHUTDOWN SUPPLY CURRENT (µA)
V
CC
= 4.75V
V
CC
= 5V
EFFICIENCY (%)
0
10
20
30
40
OUTPUT CURRENT (mA)
Supply Current vs Supply Voltage
600
I
OUT
= 0
580
SUPPLY CURRENT (µA)
OUTPUT VOLTAGE (V)
560
540
520
T
A
= 25°C
500
T
A
= 0°C
480
4.5
4.75
5.0
5.25
5.5
SUPPLY VOLTAGE (V)
5.75
6.0
PI FU CTIO S
C1
–
(Pin 1):
C1 Negative Input. Connect a 0.22µF capaci-
tor C1 between C1
+
and C1
–
.
C1
+
(Pin 2):
C1 Positive Input. Connect a 0.22µF capaci-
tor C1 between C1
+
and C1
–
.
C2
–
(Pin 3):
C2 Negative Input. Connect a 0.22µF capaci-
tor C2 between C2
+
and C2
–
.
C2
+
(Pin 4):
C2 Positive Input. Connect a 0.22µF capaci-
tor C2 between C2
+
and C2
–
.
V
CC
(Pin 5):
Positive Supply Input Where 4.75V
≤
V
CC
≤
5.5V. Connect a 4.7µF bypass capacitor C
IN
to ground.
V
OUT
(Pin 6):
12V Output. Connect a 4.7µF bypass capaci-
tor C
OUT
to ground. When in the shutdown mode V
OUT
=
V
CC
.
GND (Pin 7):
Ground.
SHDN (Pin 8):
Logic Level Shutdown Pin. Application of a
logic low at SHDN pin will place the regulator in normal
operation. With no external connection, or with SHDN tied
to V
CC
, the device will be put into shutdown mode. Connect
to GND for normal operation. In shutdown mode the
charge pump is turned off and V
OUT
= V
CC
.
U W
T
A
= 70°C
Shutdown Supply Current
vs Temperature
V
CC
= 5V
3.0
2.4
1.8
1.2
0.6
0
–50
50
LTC1262 G01
–25
0
25
50
TEMPERATURE (°C)
75
100
LTC1262 G02
Output Voltage vs Output Current
12.2
12.0
11.8
11.6
11.4
11.2
11.0
10.8
10.6
10.4
10.2
0
5
10 15 20 25 30 35 40 45 50
OUTPUT CURRENT (mA)
1262 G04
V
CC
= 4.75V
V
CC
= 5.5V
V
CC
= 5V
LTC1262 G03
U
U
U
3
LTC1262
BLOCK DIAGRAM
W
V
CC
+
S3A
C1
+
C1
C1
–
S3B
C2
+
C2
C2
–
S3D
CHARGE
PUMP
OSCILLATOR
S4B
S4A
D2
S3C
D1 S1
SHDN
V
OUT
R1
C
IN
+
R2
C
OUT
S1 AND S2 SHOWN WITH SHDN PIN LOW.
S3A, S3B, S3C, S3D, S4A AND S4B SHOWN WITH OSCILLATOR OUTPUT LOW AND V
DIV
< V
BGAP
– V
HYST
.
COMPARATOR HYSTERISIS IS
±V
HYST
.
TI I G DIAGRA S
1
t
OFF
V
OUT
5.1V
t
ON
11.4V
V
OUT
C1
0.22µF
V
CC
V
CC
C2
0.22µF
3
4
C2
–
C2
+
V
OUT
V
CC
6
5
V
SHDN
1.4V
1.4V
0V
LTC1262 • F01
V
CC
4.75V TO 5V
Figure 1. LTC1262 Timing Diagram
Figure 2. LTC1262 Timing Circuit
4
+
+
–
V
BGAP
BANDGAP
REFERENCE
V
DIV
R3
+
S2
GND
LTC1262 • BD
W
UW
C1
–
C1
+
SHDN
GND
LTC1262
8
7
V
SHUTDOWN
2
C
OUT
4.7µF
C
IN
4.7µF
V
OUT
LTC1262 • F02
LTC1262
APPLICATIONS INFORMATION
Operation
The LTC1262 uses a charge pump tripler to generate 12V
from a V
CC
of 5V. The charge pump operates when clocked
by a 300kHz oscillator. When the oscillator output is low,
C1 and C2 are connected between V
CC
and GND, charging
them to V
CC
. When the oscillator output goes high, C1 and
C2 are stacked in series with the bottom plate of C1 pulled
to V
CC
. The top plate of C2 is switched to charge C
OUT
and
V
OUT
rises. V
OUT
is regulated to within 5% of 12V by an
oscillator pulse gating scheme. A resistor divider senses
V
OUT
. When the output of the divider (V
DIV
) is less than the
output of a bandgap (V
BGAP
) by the hysteresis voltage
(V
HYST
) of the comparator, oscillator pulses are applied to
the charge pump to raise V
OUT
. When V
DIV
is above V
BGAP
by V
HYST
, the oscillator pulses are prevented from clock-
ing the charge pump. V
OUT
drops until V
DIV
is below V
BGAP
by V
HYST
again. The gates of all internal switches are
driven between V
OUT
and GND. An internal diode ensures
that the LTC1262 will start up under load by charging C
OUT
to one diode drop below V
CC
.
To reduce supply current the LTC1262 may be put into
shutdown mode by floating the SHDN pin or taking it to
V
CC
. In this mode the bandgap, comparator, oscillator and
resistor divider are switched off to reduce supply current
to typically 0.5µA. At the same time an internal switch
shorts V
OUT
to V
CC
; V
OUT
takes 3.3ms to reach 5.1V (see
t
OFF
in Figure 1). When the SHDN pin is low, the LTC1262
exits shutdown and the charge pump operates to raise
V
OUT
to 12V. V
OUT
takes 500µs to reach the lower regula-
tion limit of 11.4V (see t
ON
in Figure 1).
Choice of Capacitors
The LTC1262 is tested with the capacitors shown in
Figure 2. C1 and C2 are 0.22µF ceramic capacitors and
C
IN
and C
OUT
are 4.7µF tantalum capacitors. Refer to
Table 1 if other choices are desired.
Table 1. Recommended Capacitor Types and Values
CAPACITOR
C1, C2
C
OUT
C
IN
CERAMIC
0.22µF to 1µF
2µF (Min)
1µF (Min)
TANTALUM
Not
Recommended
4.7µF (Min)
4.7µF (Min)
ALUMINUM
Not
Recommended
10µF (Min)
10µF (Min)
U
W
U
U
C1 and C2 should be ceramic capacitors with values in the
range of 0.22µF to 1µF. Higher values provide better load
regulation. Tantalum capacitors are not recommended as
the higher ESR of these capacitors degrades performance
when the load current is above 25mA with V
CC
= 4.75V.
C
IN
and C
OUT
can be ceramic, tantalum or electrolytic
capacitors. The ESR of C
OUT
introduces steps in the V
OUT
waveform whenever the charge pump charges C
OUT
. This
tends to increase V
OUT
ripple. Ceramic or tantalum capaci-
tors are recommended for C
OUT
if minimum ripple is
desired. The LTC1262 does not require a 0.1µF capacitor
between V
CC
and V
OUT
for stability.
Maximum Load Current
The LTC1262 will source up to 50mA continuously without
any damage to itself.
Do not short the V
OUT
pin to ground.
If the V
OUT
pin is shorted to ground, irreversible damage
to the device will result.
5
NXP MCU
京公网安备 11010802033920号
EEWORLD
