Datasheet

LTC3561
4
3561f
TYPICAL PERFOR A CE CHARACTERISTICS
UW
2.5 3 3.5 4 4.5 5 5.5 6
V
IN
(V)
R
DS(ON)
(mΩ)
120
115
110
105
100
95
90
3561 G12
MAIN SWITCH
SYNCHRONOUS SWITCH
T
A
= 25°C
Frequency Variation
vs Temperature
R
DS(ON)
vs V
IN
–50 –25 0 25 50 75 100 125
TEMPERATURE (°C)
REFERENCE VARIATION (%)
10
8
6
4
2
0
–2
–4
–6
–8
–10
3561 G10
FREQUENCY (MHz)
0
85
EFFICIENCY (%)
90
95
100
12
3561 G11
34
V
IN
= 3.3V
V
OUT
= 2.5V
I
OUT
= 500mA
T
A
= 25°C
Efficiency vs Frequency
PI FU CTIO S
UUU
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
shutdown all functions are disabled.
SGND (Pin 2): The Signal Ground Pin. All small signal
components and compensation components should be
connected to this ground (see Board Layout
Considerations).
SW (Pin 3): The Switch Node Connection to the Inductor.
This pin swings from PV
IN
to PGND.
PGND (Pin 4): Main Power Ground Pin. Connect to the
(–) terminal of C
OUT
, and (–) terminal of C
IN
.
PV
IN
(Pin 5): Main Supply Pin. Must be closely decoupled
to PGND.
SV
IN
(Pin 6): 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
.
V
FB
(Pin 7): Receives the feedback voltage from the
external resistive divider across the output. Nominal
voltage for this pin is 0.8V.
I
TH
(Pin 8): Error Amplifier Compensation Point. The
current comparator threshold increases with this control
voltage. Nominal voltage range for this pin is 0V to 1.5V.
Exposed Pad (Pin 9): Thermal Connection to PCB. This
pin should be soldered to ground to achieve rated
thermal performance.