ltc3612 Linear Technology Corporation, ltc3612 Datasheet - Page 8

• Manufacturer Part Number: ltc3612
• Description: 3a, 4mhz Monolithic Synchronous Step-down Dc/dc Converter
• Manufacturer: Linear Technology Corporation

PIN FUNCTIONS
LTC3612
TYPICAL PERFORMANCE CHARACTERISTICS
DDR (Pin 1/Pin 8): DDR Mode Pin. Tying the DDR pin to
SV
an external reference input. If DDR is tied to SGND, the
internal 0.6V reference will be used.
RT/SYNC (Pin 2/Pin 9): Oscillator Frequency. This pin
provides three ways of setting the constant switching
frequency:
1. Connecting a resistor from RT/SYNC to ground will set
2. Driving the RT/SYNC pin with an external clock signal
3. Tying the RT/SYNC pin to SV
SGND (Pin 3/Pin 10): Signal Ground. All small-signal and
compensation components should connect to this ground,
which in turn should connect to PGND at a single point.
8
500mV/DIV
the switching frequency based on the resistor value.
will synchronize the LTC3612 to the applied frequency.
The slope compensation is automatically adapted to the
external clock frequency.
2.25MHz oscillator frequency.
IN
PGOOD
5V/DIV
2A/DIV
V
OUT
selects DDR mode and TRACK/SS can be used as
I
L
Start-Up from Shutdown with
Prebiased Output
(Forced Continuous Mode)
PREBIASED V
V
I
V
OUT
OUT
MODE
= 0V
= 1.2V
= 1.5V
OUT
= 2.2V
20μs/DIV
(QFN/FE)
IN
3612 G31
enables the internal
1.90
1.88
1.86
1.84
1.82
1.80
1.76
1.78
2.25
Output Voltage During Sinking
vs Input Voltage
V
1μH INDUCTOR
OUT
2.75
= 1.8V
–1.5A, 2MHz, 120°C
–1.5A, 2MHz, 25°C
3.25
INPUT VOLTAGE (V)
3.75
NC (Pins 4, 7, 10/Pins 11, 13, 18): Can be connected to
ground or left open.
SW (Pins 5, 6, 11, 12/Pins 12, 14, 17, 19): Switch Node.
Connection to the inductor. This pin connects to the drains
of the internal synchronous power MOSFET switches.
PV
connects to the source of the internal P-channel power
MOSFET. This pin is independent of SV
nected to the same voltage or to a lower voltage supply.
PV
ply. This pin must be connected to PV
SV
ers the internal control circuitry and is monitored by the
undervoltage lockout comparator.
RUN (Pin 15/Pin 2): Enable Pin. Forcing this pin to ground
shuts down the LTC3612. In shutdown, all functions are
disabled and the chip draws <1μA of supply current.
IN
IN_DRV
IN
4.25
(Pins 8, 9/Pins 15, 16): Power Input Supply. PV
(Pin 14/Pin 1): Signal Input Supply. This pin pow-
4.75
(Pin 13/Pin 20): Internal Gate Driver Input Sup-
V
IN
5.25
3612 G32
= 3.3V, RT/SYNC = SV
0.95
0.94
0.92
0.90
0.88
0.93
0.91
0.89
2.25
Output Voltage During Sinking
vs Input Voltage
V
1μH INDUCTOR
OUT
2.75
= 0.9V
IN
–1.5A, 1MHz, 120°C
–1.5A, 1MHz, 25°C
3.25
INPUT VOLTAGE (V)
unless otherwise noted.
IN
IN
3.75
.
and may be con-
4.25
4.75
5.25
3612 G33
3612f
IN