LTC1262CS8 Linear Technology, LTC1262CS8 Datasheet - Page 5

• Manufacturer Part Number: LTC1262CS8
• Description: IC DC/DC CONV FLASHMEM 12V 8SOIC
• Manufacturer: Linear Technology

Specifications of LTC1262CS8

• Applications: Converter, Programming Supply
• Voltage - Input: 4.75 ~ 5.5 V
• Number Of Outputs: 1
• Voltage - Output: 12V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

APPLICATIONS
Operation
The LTC1262 uses a charge pump tripler to generate 12V
from a V
by a 300kHz oscillator. When the oscillator output is low,
C1 and C2 are connected between V
them to V
C2 are stacked in series with the bottom plate of C1 pulled
to V
V
oscillator pulse gating scheme. A resistor divider senses
V
output of a bandgap (V
(V
the charge pump to raise V
by V
ing the charge pump. V
by V
driven between V
that the LTC1262 will start up under load by charging C
to one diode drop below V
To reduce supply current the LTC1262 may be put into
shutdown mode by floating the SHDN pin or taking it to
V
resistor divider are switched off to reduce supply current
to typically 0.5 A. At the same time an internal switch
shorts V
t
exits shutdown and the charge pump operates to raise
V
tion limit of 11.4V (see t
OFF
OUT
OUT
CC
OUT
HYST
. In this mode the bandgap, comparator, oscillator and
CC
in Figure 1). When the SHDN pin is low, the LTC1262
HYST
HYST
. When the output of the divider (V
to 12V. V
rises. V
. The top plate of C2 is switched to charge C
) of the comparator, oscillator pulses are applied to
CC
OUT
, the oscillator pulses are prevented from clock-
CC
again. The gates of all internal switches are
of 5V. The charge pump operates when clocked
. When the oscillator output goes high, C1 and
to V
OUT
OUT
CC
OUT
is regulated to within 5% of 12V by an
takes 500 s to reach the lower regula-
; V
U
and GND. An internal diode ensures
OUT
OUT
BGAP
ON
INFORMATION
takes 3.3ms to reach 5.1V (see
U
OUT
drops until V
CC
in Figure 1).
.
) by the hysteresis voltage
. When V
W
CC
and GND, charging
DIV
DIV
DIV
) is less than the
is above V
is below V
U
OUT
BGAP
BGAP
and
OUT
Choice of Capacitors
The LTC1262 is tested with the capacitors shown in
Figure 2. C1 and C2 are 0.22 F ceramic capacitors and
C
Table 1 if other choices are desired.
Table 1. Recommended Capacitor Types and Values
C1 and C2 should be ceramic capacitors with values in the
range of 0.22 F to 1 F. 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
C
capacitors. The ESR of C
waveform whenever the charge pump charges C
tends to increase V
tors are recommended for C
desired. The LTC1262 does not require a 0.1 F capacitor
between V
Maximum Load Current
The LTC1262 will source up to 50mA continuously without
any damage to itself. Do not short the V
If the V
to the device will result.
IN
IN
CAPACITOR
C1, C2
and C
and C
C
C
OUT
IN
OUT
OUT
OUT
CC
pin is shorted to ground, irreversible damage
and V
are 4.7 F tantalum capacitors. Refer to
can be ceramic, tantalum or electrolytic
0.22 F to 1 F
2 F (Min)
1 F (Min)
CERAMIC
OUT
OUT
ripple. Ceramic or tantalum capaci-
for stability.
OUT
introduces steps in the V
Recommended
OUT
TANTALUM
4.7 F (Min)
4.7 F (Min)
Not
if minimum ripple is
OUT
LTC1262
pin to ground.
Recommended
CC
ALUMINUM
10 F (Min)
10 F (Min)
= 4.75V.
OUT
Not
. This
5
OUT