LTC1624CS8 Linear Technology, LTC1624CS8 Datasheet - Page 10

• Manufacturer Part Number: LTC1624CS8
• Description: IC SW REG CONTROLLER N-CH 8-SOIC
• Manufacturer: Linear Technology
• Type: Step-Down (Buck), Step-Up (Boost), Inverting, Sepicr

Specifications of LTC1624CS8

• Internal Switch(s): No
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 1.19 ~ 30 V
• Current - Output: 2A
• Frequency - Switching: 200kHz
• Voltage - Input: 3.5 ~ 36 V
• 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
• Power - Output: -

APPLICATIONS
LTC1624
pin through a small Schottky diode (like a Central
CMDSH-3) to V
3.3V and other lower voltage regulators, additional cir-
cuitry is required to derive boost supply power from the
output.
For low input voltage operation (V
diode can be connected from V
external MOSFET gate drive voltage. Be careful not to
exceed the maximum voltage on BOOST to SW pins
of 7.8V.
Output Voltage Programming
The output voltage is set by a resistive divider according
to the following formula:
The external resistive divider is connected to the output as
shown in Figure 2, allowing remote voltage sensing. When
using remote sensing, a local 100 resistor should be
connected from L1 to R2 to prevent V
away if the sense lead is disconnected.
I
The I
loop compensation and a means to shut down the LTC1624.
Soft start can also be implemented with this pin. Soft start
reduces surge currents from V
the internal current limit. Power supply sequencing can
also be accomplished using this pin.
An internal 2.5 A current source charges up the external
capacitor C
the LTC1624 begins operating. At this point the error
amplifier pulls up the I
(assuming V
10
TH
V
/RUN Function
OUT
TH
/RUN pin is a dual purpose pin that provides the
Figure 2. Setting the LTC1624 Output Voltage
1 19 1
C.
OUT
When the voltage on I
LTC1624
V
OUT
is starting low).
U
as shown in Figure 10. However, for
GND
V
FB
TH
R
R
2
1
/RUN pin to its maximum of 2.4V
INFORMATION
U
100pF
IN
L1
IN
to BOOST to increase the
by gradually increasing
TH
W
IN
R2
R1
/RUN reaches 0.8V
< 7V), a Schottky
1624 F02
V
OUT
OUT
from running
U
Soft start can be implemented by ramping the voltage on
I
voltage on I
peak current limit is also ramped at a proportional linear
rate. The peak current limit begins at approximately
10mV/R
The output current thus ramps up slowly, charging the
output capacitor. The peak inductor current and maximum
output current are as follows:
with I
During normal operation the voltage on the I
will vary from 1.19V to 2.4V depending on the load current.
Pulling the I
a low quiescent current shutdown (I
be driven directly from logic as shown in Figures 3(a)
and 3(b).
Efficiency Considerations
The percent efficiency of a switching regulator is equal to
the output power divided by the input power times 100%.
It is often useful to analyze individual losses to determine
TH
160mV/R
I
I
/RUN during start-up as shown in Figure 3(c). As the
L(PEAK)
OUT(MAX)
L
OR 5V
SENSE
3.3V
= ripple current in the inductor.
= (V
TH
TH/RUN
SENSE
= I
Figure 3. I
(a)
/RUN pin below 0.8V puts the LTC1624 into
(at V
ITH/RUN
LPEAK
D1
(V
ramps from 1.19V to 2.4V the internal
ITH/RUN
I
ITH/RUN
TH
– I
/RUN
– 1.3V)/(6.8R
TH
R1
R
/ RUN Pin Interfacing
C
C
C1
L
C
/ 2
= 1.4V) and ends at:
(c)
= 2.4V)
D1
Q
I
TH
< 30 A). This pin can
SENSE
/RUN
R
C
C
(b)
C
)
I
TH
/RUN
TH
1624 F03
R
/RUN pin
C
C
C