LTC3204EDC-3.3#TRMPBF Linear Technology, LTC3204EDC-3.3#TRMPBF Datasheet - Page 7

• Manufacturer Part Number: LTC3204EDC-3.3#TRMPBF
• Description: IC SW CAP/DBLR 3.3V 50MA 6DFN
• Manufacturer: Linear Technology
• Type: Switched Capacitor (Charge Pump), Doublerr

Specifications of LTC3204EDC-3.3#TRMPBF

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 3.3V
• Current - Output: 50mA
• Frequency - Switching: 1.2MHz
• Voltage - Input: 1.8 ~ 4.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 6-DFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Other names: LTC3204EDC-3.3#PBF; LTC3204EDC-3.3#PBF

OPERATIO
The LTC3204-3.3/LTC3204-5/LTC3204B-3.3/LTC3204B-5
use a switched capacitor charge pump to boost V
regulated output voltage. Regulation is achieved by sensing
the output voltage through an internal resistor divider and
modulating the charge pump output current based on the
error signal. A 2-phase nonoverlapping clock activates the
charge pump switches. The flying capacitor is charged from
V
of the clock it is stacked in series with V
to V
flying capacitor continues at a free running frequency of
1.2MHz (typ).
Shutdown Mode
In shutdown mode, all circuitry is turned off and the
LTC3204-3.3/LTC3204-5/LTC3204B-3.3/LTC3204B-5
draws only leakage current from the V
more, V
CMOS input with a threshold voltage of approximately 0.7V.
The LTC3204-3.3/LTC3204-5/LTC3204B-3.3/LTC3204B-5
are in shutdown when a logic low is applied to the  S  H  D  N
pin. Since the  S  H  D  N pin is a very high impedance CMOS
input, it should never be allowed to float. To ensure that
its state is defined, it must always be driven with a valid
logic level.
Since the output voltages of these devices can go above
the input voltage, special circuitry is required to control
the internal logic. Detection logic will draw an input current
of 5µA when the devices are in shutdown. However, this
current will be eliminated if the output voltage (V
less than approximately 0.8V.
Burst Mode Operation
The LTC3204-3.3/LTC3204-5 provide automatic Burst
Mode operation to reduce supply current at light loads.
Burst Mode operation is initiated if the output load current
falls below an internally programmed threshold. Once
IN
on the first phase of the clock. On the second phase
OUT
. This sequence of charging and discharging the
OUT
is disconnected from V
U
(Refer to the Block Diagram)
IN
. The  S  H  D  N pin is a
IN
IN
supply. Further-
and connected
OUT
IN
to a
) is
Burst Mode operation is initiated, the part shuts down
the internal oscillator to reduce the switching losses and
goes into a low current state. This state is referred to as
the sleep state in which the IC consumes only about 40µA
from the input. When the output voltage droops enough
to overcome the burst comparator hysteresis, the part
wakes up and commences normal fixed frequency opera-
tion. The output capacitor recharges and causes the part
to reenter the sleep state if the output load still remains
less than the Burst Mode threshold. This Burst Mode
threshold varies with V
storage capacitor.
Soft-Start
The LTC3204-3.3/LTC3204-5/LTC3204B-3.3/LTC3204B-5
have built-in soft-start circuitry to prevent excessive current
flow during start-up. The soft-start is achieved by charging
an internal capacitor with a very weak current source. The
voltage on this capacitor, in turn, slowly ramps the amount
of current available to the output storage capacitor from
zero to a value of 300mA over a period of approximately
0.75ms. The soft-start circuit is reset in the event of a
commanded shutdown or thermal shutdown.
Short-Circuit/Thermal Protection
The LTC3204-3.3/LTC3204-5/LTC3204B-3.3/LTC3204B-5
have built-in short-circuit current limit as well as over-tem-
perature protection. During a short-circuit condition, they
will automatically limit their output current to approximately
300mA. At higher temperatures, or if the input voltage is
high enough to cause excessive self-heating of the part,
the thermal shutdown circuitry will shutdown the charge
pumponcethejunctiontemperatureexceedsapproximately
160°C. It will enable the charge pump once the junction
temperature drops back to approximately 150°C. The
LTC3204-3.3/LTC3204-5/LTC3204B-3.3/LTC3204B-5 will
cycle in and out of thermal shutdown indefinitely without
latchup or damage until the short-circuit condition on
V
OUT
LTC3204B-3.3/LTC3204B-5
is removed.
LTC3204-3.3/LTC3204-5/
IN
, V
OUT
and the choice of output
3204fa
7