LTC3704IMS#TRPBF Linear Technology, LTC3704IMS#TRPBF Datasheet - Page 10

• Manufacturer Part Number: LTC3704IMS#TRPBF
• Description: IC INV SYNC 5.2V 50MA 10MSOP
• Manufacturer: Linear Technology
• Type: Invertingr

Specifications of LTC3704IMS#TRPBF

• Internal Switch(s): No
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: -5.2V
• Current - Output: 50mA
• Frequency - Switching: 50kHz ~ 1MHz
• Voltage - Input: 2.5 ~ 36 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 10-MSOP, Micro10™, 10-uMAX, 10-uSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -

APPLICATIO S I FOR ATIO
LTC3704
Programming the Operating Frequency
The choice of operating frequency and inductor value is a
tradeoff between efficiency and component size. Low
frequency operation improves efficiency by reducing
MOSFET and diode switching losses. However, lower
frequency operation requires more inductance for a given
amount of load current.
The LTC3704 uses a constant frequency architecture that
can be programmed over a 50kHz to 1000kHz range with
a single external resistor from the FREQ pin to ground, as
shown in Figure 1. The nominal voltage on the FREQ pin is
0.6V, and the current that flows into the FREQ pin is used
to charge and discharge an internal oscillator capacitor. A
graph for selecting the value of R
frequency is shown in Figure 6.
10
MODE/
SYNC
GATE
I
SW
Figure 5. MODE/SYNC Clock Input and Switching
Waveforms for Synchronized Operation
1000
100
10
Figure 6. Timing Resistor (R
0
100
t
MIN
200
U
= 25ns
300
FREQUENCY (kHz)
400
U
D = 40%
500
600
0.8T
T
700
W
for a given operating
800
T
T
) Value
900
3704 F06
T = 1/f
3404 F05
1000
O
2V TO 7V
U
1.230V
For input voltages that don’t exceed 7V (the absolute
maximum rating for this pin), the internal low dropout
regulator in the LTC3704 is redundant and the INTV
can be shorted directly to the V
shorted to V
regulated INTV
the input supply, even in shutdown mode. For applications
that require the lowest shutdown mode input supply
current, do not connect the INTV
of whether the INTV
always necessary to have the driver circuitry bypassed
with a 4.7μF tantalum or low ESR ceramic capacitor to
ground immediately adjacent to the INTV
pins.
In an actual application, most of the IC supply current is
used to drive the gate capacitance of the power MOSFET.
As a result, high input voltage applications in which a large
power MOSFET is being driven at high frequencies can
INTV
An internal, P-channel low dropout voltage regulator pro-
duces the 5.2V supply which powers the gate driver and
logic circuitry within the LTC3704, as shown in Figure 7.
The INTV
bypassed to ground immediately adjacent to the IC pins
with a minimum of 4.7μF tantalum or ceramic capacitor.
Good bypassing is necessary to supply the high transient
currents required by the MOSFET gate driver.
R2
Figure 7. Bypassing the LDO Regulator and Gate Driver Supply
CC
–
+
LOGIC
Regulator Bypassing and Operation
CC
regulator can supply up to 50mA and must be
IN
, however, the divider that programs the
CC
R1
voltage will draw 10μA of current from
DRIVER
CC
P-CH
5.2V
pin is shorted to V
INTV
GATE
GND
V
CC
IN
IN
CC
pin. With the INTV
POSSIBLE TO DEVICE PINS
pin to V
+
PLACE AS CLOSE AS
C
4.7μF
VCC
IN
IN
CC
. Regardless
or not, it is
C
and GND
IN
M1
CC
CC
INPUT
SUPPLY
2.5V TO
30V
GND
3704fb
3704 F07
pin
pin