Datasheet

LTC3215
5
3215fc
Charge Pump Mode Switching
and Input Current (I
LED
= 400mA) Efficiency vs V
IN
I
SET
/I
LED
Current Ratio
vs I
LED
Current
TYPICAL PERFORMANCE CHARACTERISTICS
PIN FUNCTIONS
C2
+
, C1
+
, C2
–
, C1
–
(Pins 1, 2, 8, 10): Charge Pump
Flying Capacitor Pins. A 2.2µF X5R or X7R ceramic ca-
pacitor should be connected from C1
+
to C1
–
and from
C2
+
to C2
–
.
CPO (Pin 3): Output. CPO is the output of the Charge
Pump. This pin may be enabled or disabled using the EN
input. A 4.7µF X5
R or X7R ceramic capacitor is required
from CPO to GND.
I
LED
(Pin 4): Output. I
LED
is the LED current source
output. The LED is connected between CPO (anode) and
I
LED
(cathode). The current into the I
LED
pin is set by the
programming resistor connected from I
SET
to GND.
I
SET
(Pin 5): LED Current Programming Resistor Pin. The
I
SET
pin will servo to 1.22V. A resistor connected between
this pin and GND is used to set the LED current level. Con-
necting a resistor of 2k or less will cause the LTC3215 to
enter overcurrent shutdown mode.
EN (Pin 6): Input. The EN is used to enable the part or put
it into shutdown mode.
V
IN
(Pin 7): Power. Supply voltage for the LTC3215. V
IN
should be bypassed with
a 2.2µF or greater low impedance
ceramic capacitor to GND.
GND (Pin 9): Charge Pump Ground. This pin should be
connected directly to a low impedance ground plane.
EXPOSED PAD (Pin 11): Control Signal Ground. This pad
must be soldered to a low impedance ground plane for
optimum thermal and electrical performance.
(T
A
= 25°C unless otherwise specified)
V
CPO
1V/DIV
I
VIN
500mA/
DIV
V
IN
= 3V 1ms/DIV
3215 G12
EN2
5V/DIV
V
IN
(V)
2.8
EFFICIENCY (P
LED
/P
IN
) (%)
100
90
80
70
60
50
40
30
20
10
0
3.2
3.6
3.8
3215 G13
3.0 3.4
4.0
4.2
4.4
AOT2015
V
F
= 3V TYP AT 200mA
100mA
200mA
400mA
I
LED
CURRENT (mA)
0
3100
CURRENT RATIO
3150
3200
3250
–40°C
25°C
85°C
3300
200 400
600
800
3215 G14
3350
3400