LTC1517CS5-3.3#TRPBF Linear Technology, LTC1517CS5-3.3#TRPBF Datasheet - Page 5

• Manufacturer Part Number: LTC1517CS5-3.3#TRPBF
• Description: IC CHARGE PUMP REG 3.3V SOT23-5
• Manufacturer: Linear Technology
• Type: Switched Capacitor (Charge Pump)r

Specifications of LTC1517CS5-3.3#TRPBF

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 3.3V
• Current - Output: 15mA
• Frequency - Switching: 700kHz
• Voltage - Input: 2 ~ 4.4 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: SOT-23-5, SC-74A, SOT-25
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -

APPLICATIONS
Operation
The LTC1517-3.3 uses a switched-capacitor charge pump
to boost V
achieves regulation by sensing the output voltage through
an internal resistor divider and enabling the charge pump
when the divided output droops below the comparator’s
lower trip point (set by V
enabled, a 2-phase nonoverlapping clock controls the
internal charge pump switches. Flying capacitor C1 is
charged to V
the clock, C1 is stacked in series with V
to V
charging and discharging the flying capacitor occurs at a
free running frequency of 700kHz (typ) and continues until
the divided output voltage reaches the upper trip point of
the comparator. Once the output is back in regulation, the
charge pump is disabled. This method of bursting the
charge pump on and off enables the LTC1517-3.3 to
achieve high efficiency at extremely low output loads.
Capacitor Selection
For best performance, it is recommended that low ESR
capacitors be used for both C
and ripple. The C
ceramic or tantalum and should be 3.3 F or greater.
Ceramic capacitors will provide the smallest size for a
given capacitance. If the input source impedance is very
low (< 0.5 ), C
are recommended for the flying capacitor C1 with values
of 0.1 F or 0.22 F. Smaller value flying capacitors may be
used in low I
OUT
through an internal switch. This sequence of
IN
IN
OUT
to a 3.3V 4% regulated output. The part
on phase one of the clock. On phase two of
IN
IN
applications.
may not be needed. Ceramic capacitors
U
and C
INFORMATION
REF
OUT
U
). When the charge pump is
IN
capacitors should be either
and C
W
OUT
IN
to reduce noise
and connected
U
Output Ripple
Normal LTC1517-3.3 operation produces voltage ripple
on the V
parts to regulate. Low frequency ripple exists due to the
hysteresis in the sense comparator and propagation de-
lays in the charge pump enable/disable circuits. High
frequency ripple is also present mainly from the ESR
(equivalent series resistance) in the output capacitor.
Typical output ripple with V
is 75mV peak-to-peak with a low ESR 3.3 F output capaci-
tor (minimum recommended C
requiring V
less than 75mV of peak-to-peak ripple, a 6.8 F to 10 F
C
in output ripple can be achieved by using C
larger than 10 F.
Short-Circuit/Thermal Protection
During short-circuit conditions, the LTC1517-3.3 will draw
between 20mA and 150mA from V
junction temperature. On-chip thermal shutdown circuitry
disables the charge pump once the junction temperature
exceeds approximately 160 C. The charge pump is
reenabled once the junction temperature drops to approxi-
mately 145 C. The LTC1517-3.3 will cycle in and out of
thermal shutdown indefinitely without latchup or damage
until the V
OUT
capacitor is recommended. Slight further decreases
OUT
OUT
IN
pin. Output voltage ripple is required for the
to exceed 3.3V or for applications requiring
short is removed.
IN
= 2.5V under maximum load
OUT
LTC1517-3.3
IN
). For applications
, causing a rise in
OUT
capacitors
5