LTC3411 Datasheet, PDF (3/20 Pages) Linear Technology – 1.25A, 4MHz, Synchronous Step-Down DC/DC Converter

LTC3411
ELECTRICAL CHARACTERISTICS The q denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T_A = 25°C. V_IN = 3.3V, R_T = 324k unless otherwise specified. (Note 2)
SYMBOL
PARAMETER
CONDITIONS
MIN TYP MAX
PGOOD
R_PGOOD
Power Good Threshold
Power Good Pull-Down On-Resistance
V_FB Ramping Up, SHDN/R_T = 1V
V_FB Ramping Down, SHDN/R_T = 1V
6.8
– 7.6
118
200
UNITS
%
%
Ω
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: The LTC3411E is guaranteed to meet specified performance from
0°C to 70°C. Specifications over the – 40°C to 85°C operating ambient
termperature range are assured by design, characterization and correlation
with statistical process controls.
Note 3: The LTC3411 is tested in a feedback loop which servos V_FB to the
midpoint for the error amplifier (V_ITH = 0.6V).
Note 4: Dynamic supply current is higher due to the internal gate charge
being delivered at the switching frequency.
Note 5: T_J is calculated from the ambient T_A and power dissipation P_D
according to the following formula:
LTC3411EDD: T_J = T_A + (P_D • 43°C/W)
LTC3411EMS: T_J = T_A + (P_D • 120°C/W)
Note 6: Switch on-resistance is guaranteed by correlation to wafer level
measurements.
Note 7: 4MHz operation is guaranteed by design but not production tested
and is subject to duty cycle limitations (see Applications Information).
Note 8: This IC includes overtemperature protection that is intended to
protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.
PI FU CTIO S
SHDN/R_T (Pin 1): Combination Shutdown and Timing
Resistor Pin. The oscillator frequency is programmed by
connecting a resistor from this pin to ground. Forcing this
pin to SV_IN causes the device to be shut down. In shut-
down all functions are disabled.
SYNC/MODE (Pin 2): Combination Mode Selection and
Oscillator Synchronization Pin. This pin controls the op-
eration of the device. When tied to SV_IN or SGND, Burst
Mode operation or pulse skipping mode is selected, re-
spectively. If this pin is held at half of SV_IN, the forced
continuous mode is selected. The oscillation frequency
can be syncronized to an external oscillator applied to this
pin. When synchronized to an external clock pulse skip
mode is selected.
SGND (Pin 3): The Signal Ground Pin. All small signal
components and compensation components should be
connected to this ground (see Board Layout Consider-
ations).
SW (Pin 4): The Switch Node Connection to the Inductor.
This pin swings from PV_IN to PGND.
PGND (Pin 5): Main Power Ground Pin. Connect to the
(–) terminal of C_OUT, and (–) terminal of C_IN.
PV_IN (Pin 6): Main Supply Pin. Must be closely decoupled
to PGND.
SV_IN (Pin 7): The Signal Power Pin. All active circuitry is
powered from this pin. Must be closely decoupled to
SGND. SV_IN must be greater than or equal to PV_IN.
PGOOD (Pin 8): The Power Good Pin. This common drain
logic output is pulled to SGND when the output voltage is
not within ±7.5% of regulation.
V_FB (Pin 9): Receives the feedback voltage from the
external resistive divider across the output. Nominal volt-
age for this pin is 0.8V.
I_TH (Pin 10): Error Amplifier Compensation Point. The
current comparator threshold increases with this control
voltage. Nominal voltage range for this pin is 0V to 1.5V.
sn3411 3411fs
3