LTC3450 Datasheet, PDF (6/12 Pages) Linear Technology – Triple Output Power Supply for Small TFT-LCD Displays

LTC3450
PI FU CTIO S
C3⁺ (Pin 1): Charge Pump Inverter Flying Capacitor Posi-
tive Node. The charge pump inverter flying capacitor is
connected between C3⁺ and C3^–. The voltage on C3⁺ will
alternate between GND and V_INV at an approximate 50%
duty cycle while the inverting charge pump is operating.
Use a 10nF or larger X5R type ceramic capacitor for best
results.
C3^– (Pin 2): Charge Pump Inverter Flying Capacitor Nega-
tive Node. The charge pump inverter flying capacitor is
connected between C3⁺ and C3^–. The voltage on C3^– will
alternate between GND and V_NEG at an approximate 50%
duty cycle while the inverting charge pump is operating.
Use a 10nF or larger X5R type ceramic capacitor for best
results.
V_NEG (Pin 3): Charge Pump Inverter Output. V_NEG can be
either – 5V or –10V depending on where V_INV is con-
nected. V_NEG should be bypassed to GND with at 0.1µF or
larger X5R type ceramic capacitor. V_NEG can also be
configured for –15V with two external low current Schottky
diodes (see Applications section).
MODE (Pin 4): Drive MODE high to force the LTC3450 into
high power (scan) mode. Drive MODE low to force the
LTC3450 into low power (blank) mode. The output volt-
ages remain active with the MODE pin driven low but with
reduced output current capability. MODE must be pulled
up to V_IN or higher on initial application of power in order
for proper initialization to occur.
SHDN (Pin 5): Master Shutdown Input for the LTC3450.
Driving SHDN low disables all IC functions and reduces
quiescent current from the battery to less than 2µA. Each
generated output voltage is actively discharged to GND in
shutdown through internal pull down devices. An optional
RC network on SHDN provides a slower ramp up of the
boost converter inductor current during startup (soft-start).
V_IN (Pin 6): Input Supply to the LTC3450. Connect V_IN to
a voltage source between 1.5V and 4.6V. Bypass V_IN to
GND with a 2.2µF X5R ceramic capacitor.
V_OUT (Pin 7): Main 5.1V Output of the Boost Regulator and
Input to the Voltage Doubler Stage. Bypass V_OUT with a low
ESR, ESL ceramic capacitor (X5R type) between 2.2µF and
10µF.
SW (Pin 8): Switch Pin. Connect the inductor between SW
and V_IN. Keep PCB trace lengths as short and wide as
possible to reduce EMI and voltage overshoot. If the
inductor current falls to zero, the internal P-channel
MOSFET synchronous rectifier is turned off to prevent
reverse charging of the inductor and an internal switch
connects SW to V_IN to reduce EMI.
GND (Pin 9): Signal and Power Ground for the LTC3450.
Provide a short direct PCB path between GND and the
(–) side of the output filter capacitor(s) on V_OUT, V2X, V3X
and V_NEG.
C1^– (Pin 10): Charge Pump Doubler Flying Capacitor
Negative Node. The charge pump doubler flying capacitor
is connected between C1⁺ and C1^–. The voltage on C1^– will
alternate between GND and V_OUT at an approximate 50%
duty cycle while the charge pump is operating. Use a 10nF
or larger X5R type ceramic capacitor for best results.
C1⁺ (Pin 11): Charge Pump Doubler Flying Capacitor
Positive Node. The charge pump doubler flying capacitor
is connected between C1⁺ and C1^–. The voltage on C1⁺ will
alternate between V_OUT and V2X at an approximate 50%
duty cycle while the charge pump is operating. Use a 10nF
or larger X5R type ceramic capacitor for best results.
V2X (Pin 12): Charge Pump Doubler Output. This output
is 10.2V (nom) at no load and is capable of delivering up
to 500µA to a load. V2X should be bypassed to GND with
a 0.47µF X5R type ceramic capacitor.
C2^– (Pin 13): Charge Pump Tripler Flying Capacitor Nega-
tive Node. The charge pump tripler flying capacitor is
connected between C2⁺ and C2^–. The voltage on C2^– will
alternate between GND and V_OUT at an approximate 50%
duty cycle while the charge pump is operating. Use a 10nF
or larger X5R type ceramic capacitor for best results.
C2⁺ (Pin 14): Charge Pump Tripler Flying Capacitor Posi-
tive Node. The charge pump tripler flying capacitor is
connected between C2⁺ and C2^–. The voltage on C2⁺ will
alternate between V2X and V3X at an approximate 50%
duty cycle while the charge pump is operating. Use a 10nF
or larger X5R type ceramic capacitor for best results.
3450f
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