LTC3230_15 Datasheet, PDF (7/16 Pages) Linear Technology – 5-LED Main/Sub Display Driver with Dual LDO

LTC3230
PIN FUNCTIONS
CPO (Pin 1): Output of the Charge Pump Used to Power
All LEDs. This pin is enabled or disabled using the ENM
and ENS inputs. A 1μF X5R or X7R ceramic capacitor
should be connected to ground.
ENLDO1, ENLDO2 (Pins 2, 3): LDO1 and LDO2 Enables.
Logic-level high enables LDO1 or LDO2. Logic-level low
disables LDO1 or LDO2.
R_SET (Pin 4): LED Current Programming Resistor Pin. The
R_SET pin will servo to 0.8V. A resistor connected between
R_SET and GND is used to set the MLED and SLED full-scale
current level. Connecting a resistor 10k or less will cause
the LTC3230 to enter overcurrent shutdown.
ENS, ENM (Pins 5, 11): SLED and MLED Enable and Output
Control. The ENS and ENM pins are used to program the
LED output currents. Pulse the ENS pin up to 31 times to
decrement the internal 5-bit DAC which controls the Sub
LED current from full scale to one LSB. Pulse the ENM pin
up to 31 times to decrement the internal 5-bit DAC which
controls the MLED1-4 LED currents from full scale to one
LSB. The counters will stop at 1LSB when the number of
strobes exceeds 31. The pin must be held high after the
desired positive strobe edge and the data is transferred
after a 150μs (typical) delay. Holding the ENS or ENM
pin low will clear the counter for the selected display and
reset the LED current to zero. If both inputs are held low
for longer than 150μs (typical), the charge pump and LED
current sources will go into shutdown. The charge pump
mode is reset to 1x whenever ENS or ENM is held low or
when the part is shut down.
SLED (Pin 6): SLED Current Driver. SLED is the Sub cur-
rent source output. The LED is connected between CPO
(anode) and SLED (cathode). The current to the LED output
is set via the ENS input.
MLED1, MLED2, MLED3, MLED4 (Pins 7, 8, 9, 10):
MLED1-4 Current Drivers. MLED1 to MLED4 are the Main
current source outputs. The LEDs are connected between
CPO (anodes) and MLED1-4 (cathodes). The current to
the LED outputs are set via the ENM input. Any of the four
LED outputs can be disabled by connecting the output
directly to CPO. A 100μA current will flow through each
directly connected LED output.
V2, V1 (Pins 12, 13): LDO Output Voltage Select. V1 is
used to set LDO1’s output voltage. V2 is used to set LDO2’s
output voltage. Tie to V_IN, GND or float. LDO Output volt-
ages set by V1 and V2 are shown below.
V1
GND
FLOAT
V_IN
LDO1 (V)
1.2
1.5
1.8
V2
GND
FLOAT
V_IN
LDO2 (V)
1.8
2.8
3.3
LDO2, LDO1 (Pins 14, 15): LDO Outputs. Bypass LDO1 and
LDO2 with 1μF X5R or X7R ceramic capacitors to GND.
C2M, C1M, C2P, C1P (Pins 16, 17, 19, 20): Charge
Pump Flying Capacitor Pins. 1μF X5R or X7R ceramic
capacitors should be connected from C1P to C1M and
from C2P and C2M.
V_IN (Pin 18): Supply Voltage. This pin should be bypassed
with a 2.2μF or greater low ESR ceramic capacitor.
Exposed Pad (Pin 21): Ground. This pad must be con-
nected directly to a low impedance ground plane for proper
thermal and electrical performance.
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