LTC1751-3.3_15 Datasheet, PDF (1/12 Pages) Linear Technology – Micropower, Regulated Charge Pump DC/DC Converters

LTC1751/LTC1751-3.3/LTC1751-5
Micropower, Regulated
Charge Pump
DC/DC Converters
FEATURES
s _{5V Output Current: 100mA (VIN ≥ 3V)}
s _{3.3V Output Current: 80mA (VIN ≥ 2.5V)}
s _{Ultralow Power: 20µA Quiescent Current}
s _{Regulated Output Voltage: 3.3V ±4%, 5V ±4%, ADJ}
s _{No Inductors}
s _{Short-Circuit/Thermal Protection}
s _{VIN Range: 2V to 5.5V}
s _{800kHz Switching Frequency}
s _{Very Low Shutdown Current: <2µA}
s _{Shutdown Disconnects Load from VIN}
s _{PowerGood/Undervoltage Output}
s _{Adjustable Soft-Start Time}
s _{Available in an 8-Pin MSOP Package}
U
APPLICATIO S
s _{Li-Ion Battery Backup Supplies}
s _{Local 3V and 5V Conversion}
s _{Smart Card Readers}
s _{PCMCIA Local 5V Supplies}
s _{White LED Backlighting}
DESCRIPTIO
The LTC^®1751 family are micropower charge pump DC/
DC converters that produce a regulated output voltage at
up to 100mA. The input voltage range is 2V to 5.5V.
Extremely low operating current (20µA typical with no
load) and low external parts count (one flying capacitor
and two small bypass capacitors at V_IN and V_OUT) make
them ideally suited for small, battery-powered applica-
tions.
The LTC1751 family operate as Burst Mode^TM switched
capacitor voltage doublers to achieve ultralow quiescent
current. They have thermal shutdown capability and can
survive a continuous short circuit from V_OUT to GND. The
PGOOD pin on the LTC1751-3.3 and LTC1751-5 indicates
when the output voltage has reached its final value and if
the output has an undervoltage fault condition. The FB pin
of the adjustable LTC1751 can be used to program the
desired output voltage or current. An optional soft-start
capacitor may be used at the SS pin to prevent excessive
inrush current during start-up.
The LTC1751 family is available in an 8-pin MSOP
package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a trademark of Linear Technology Corporation.
TYPICAL APPLICATIO
Regulated 5V Output from a 2.7V to 5.5V Input
V_IN
2.7V
TO 5.5V ^C2
10µF
OFF ON
3
V_IN
2
V_OUT
7
1
SHDN PGOOD
8
LTC1751-5
SS
C⁺
6
4
GND
C^{– 5}
R1
100k
PGOOD
C_FLY
1µF
1751 TA01
C_FLY = MURATA GRM39X5R105K6.3AJ
C1, C2 = MURATA GRM40X5R106K6.3AJ
V_OUT
C1
10µF
5V ±4%
I_OUT ≤ 100mA, V_IN ≥ 3V
I_OUT ≤ 50mA, V_IN ≥ 2.7V
Output Voltage vs Input Voltage
5.2
I_OUT = 50mA
C_FLY = 1µF
C_OUT = 10µF
5.1
T_A = 85°C
5.0
T_A = 25°C
T_A = –40°C
4.9
4.8
2.5
3.0 3.5 4.0 4.5
INPUT VOLTAGE (V)
5.0 5.5
1751 TA02
1