LT1534-1 LINER [Linear Technology], LT1534-1 Datasheet - Page 6

• Manufacturer Part Number: LT1534-1
• Description: Ultralow Noise 2A Switching Regulators
• Manufacturer: LINER [Linear Technology]

PIN
LT1534/LT1534-1
COL (Pins 2, 15/Pin 2): These two pins should be con-
nected together externally to create the collector of the
power switch. The emitter returns to PGND through a
sense resistor. Large currents flow into these pins so it is
desirable to keep external trace lengths short to minimize
radiation.
SYNC (Pin 4): The SYNC pin can be used to synchronize
the oscillator to an external clock (see Oscillator Sync in
Applications Information section for more details). The
SYNC pin may either be floated or tied to ground if not
used.
C
conjunction with R
For R
R
charge and discharge currents of the oscillator capacitor.
The nominal value is 16.9k. It is possible to adjust this
resistance 25% to get a more accurate oscillator fre-
quency.
FB (Pin 7): The feedback pin is used for positive voltage
sensing and oscillator frequency shifting during start-up
and short-circuit conditions. It is the inverting input to the
error amplifier. The noninverting input of this amplifier
connects internally to a 1.25V reference. This pin should
be left open if not used.
NFB (Pin 8/Pin 10): The negative voltage feedback pin is
used for sensing a negative output voltage. The pin is
connected to the inverting input of the negative feedback
amplifier through a 100k source resistor. The negative
feedback amplifier provides a gain of – 0.5 to the feedback
amplifier; therefore, the nominal regulation point is – 2.5V
on NFB. This pin should be left open if not used.
GND (Pin 9/Pins 1, 8, 9, 16): Signal Ground. The internal
error amplifier, negative feedback amplifier, oscillator,
slew control circuitry and the bandgap reference are
6
T
T
C
U
(Pin 6): The oscillator resistor pin is used to set the
(Pin 5): The oscillator capacitor pin is used in
T(NF)
T
FUNCTIONS
= 16.9k,
= 129/f
U
OSC(kHz)
T
U
to set the oscillator frequency.
(LT1534/LT1534-1)
referred to this ground. Keep the connection to the feed-
back divider and V
ground currents.
V
frequency compensation and current limiting. It is the
output of the error amplifier and the input of the current
comparator. Loop frequency compensation can be per-
formed with an RC network connected from the V
ground.
SHDN (Pin 11/Pin 12): The shutdown pin is used for
disabling the switcher. Grounding this pin will disable all
internal circuitry. Normally this output can be tied high (to
V
R
slew rate for the power switch. The minimum resistor
value is 3.9k and the maximum value is 68k. Current slew
will be approximately:
R
slew rate for the power switch collector. The minimum
resistor value is 3.9k and the maximum value is 68k.
Voltage slew will be approximately:
V
a 4.7 F low ESR capacitor. When V
part will go into undervoltage lockout where it will stop
output switching and pull the V
PGND (Pin 16/Pin 3): Power Switch Ground. This ground
comes from the emitters of the power switches. In normal
operation this pin should have approximately 25nH induc-
tance to ground. This can be done by trace inductance
(approximately 1") or with wire or a specific inductive
component (e.g., small ferrite bead). This inductance
ensures stability in the current slew control loop during
turn-off. Too much inductance (>50nH) may produce
oscillation on the output voltage slew edges.
C
IN
IN
CSL
VSL
I
V
) or may be left floating.
SLEW(A/ s)
(Pin 10/Pin 11): The compensation pin is used for
(Pin 14/Pin 15): Input Supply Pin. Bypass this pin with
SLEW(V/ s)
(Pin 12/Pin 13): A resistor to ground sets the current
(Pin 13/Pin 14): A resistor to ground sets the voltage
= 33/R
= 220/R
C
compensation network free of large
CSL(k )
VSL(k )
C
pin low.
IN
is below 2.55V the
C
pin to