LTC1871EMS-7 Linear Technology, LTC1871EMS-7 Datasheet - Page 12

• Manufacturer Part Number: LTC1871EMS-7
• Description: IC MULTI CONFIG SYNC ADJ 10MSOP
• Manufacturer: Linear Technology
• Type: Step-Up (Boost), Flyback, Sepicr

Specifications of LTC1871EMS-7

• Internal Switch(s): No
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 1.23 ~ 36 V
• Current - Output: 50mA
• Frequency - Switching: 50kHz ~ 1MHz
• Voltage - Input: 6 ~ 36 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 10-MSOP, Micro10™, 10-uMAX, 10-uSOP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Power - Output: -

LTC1871-7
OPERATION
The resistors R1 and R2 are typically chosen so that the
error caused by the current fl owing into the FB pin dur-
ing normal operation is less than 1% (this translates to a
maximum value of R1 of about 250k).
Programming Turn-On and Turn-Off Thresholds with
the RUN Pin
The LTC1871-7 contains an independent, micropower volt-
age reference and comparator detection circuit that remains
active even when the device is shut down, as shown in
Figure 8. This allows users to accurately program an input
voltage at which the converter will turn on and off. The
falling threshold voltage on the RUN pin is equal to the
internal reference voltage of 1.248V. The comparator has
100mV of hysteresis to increase noise immunity.
12
LOGIC CONTROL
Figure 8b. On/Off Control Using External Logic
EXTERNAL
RUN
SUPPLY
Figure 8a. Programming the Turn-On and Turn-Off Thresholds Using the RUN Pin
INPUT
6V
1.248V
+
–
CAPACITOR
OPTIONAL
FILTER
+
–
18717 F08b
COMPARATOR
RUN
R2
R1
V
RUN
GND
IN
REFERENCE
μPOWER
6V
1.248V
The turn-on and turn-off input voltage thresholds are
programmed using a resistor divider according to the
following formulas:
The resistor R1 is typically chosen to be less than 1M.
For applications where the RUN pin is only to be used as
a logic input, the user should be aware of the 7V Absolute
Maximum Rating for this pin! The RUN pin can be con-
nected to the input voltage through an external 1M resistor,
as shown in Figure 8c, for “always on” operation.
V
V
IN(OFF)
IN(ON)
+
–
SUPPLY
INPUT
Figure 8c. External Pull-Up Resistor On
RUN Pin for “Always On” Operation
= 1.348V • 1+
COMPARATOR
= 1.248V • 1+
+
–
RUN
1M
R2
START-UP
BIAS AND
CONTROL
V
RUN
GND
IN
R2
R1
18717 F8a
R2
R1
1.248V
6V
+
–
COMPARATOR
RUN
18717 F08c
18717fc