LTC3205
Multidisplay
LED Controller
FEATURES
s
s
DESCRIPTIO
s
s
s
s
s
s
s
s
s
s
Step-Up/Step-Down Fractional Charge Pump for Up
to 92% Efficiency
Independent Current and Dimming Control for
1-4 LED Main, 1-2 LED Sub and RGB LED Displays
LED Currents Programmable Using 3-Wire Serial
Interface
Up to 250mA of Continuous LED Current
0.7% LED Current Matching
Low Noise Constant Frequency Operation*
Minimal Component Count
Automatic Soft-Start Limits Inrush Current
Four Programmable Dimming States for Main and
Sub Displays
Up to 4096 Color Combinations for RGB Display
Low Shutdown Current: I
CC
< 1µA
Tiny 24-Lead (4mm
×
4mm) QFN Package
The LTC
®
3205 is a highly integrated multidisplay LED con-
troller. The part contains a high efficiency, low noise frac-
tional step-up/step-down charge pump to provide power
for both main and sub white LED displays plus an RGB
color LED display. The LTC3205 requires only four small
ceramic capacitors plus two resistors to form a complete
3-display LED power supply and current controller.
Maximum currents for the main/sub and RGB displays are
set independently with a single resistor. Current for each
LED is controlled with an internal current source. Dim-
ming and ON/OFF control for all displays are achieved via
a 3-wire serial interface. Four dimming states exist for the
main and sub displays and 16 dimming states are available
via internal PWM for the red, green and blue LEDs result-
ing in up to 4096 color combinations.
The LTC3205 charge pump optimizes efficiency based on
V
IN
and LED forward voltage conditions. The part powers
up in step-down mode and automatically switches to step-
up mode once any enabled LED current source begins to
enter dropout. Internal circuitry prevents inrush current and
excess input noise during start-up and mode switching.
The LTC3205 is available in a low profile 24-lead
(4mm
×
4mm
×
0.8mm) QFN package.
APPLICATIO S
s
s
s
Cellular Phones
Wireless PDAs
Multidisplay Handheld Devices
, LTC and LT are registered trademarks of Linear Technology Corporation.
* U.S. Patent 6,411,531
TYPICAL APPLICATIO
1µF
1µF
V
IN
1µF
LTC3205
CPO
1µF
EFFICIENCY (P
LED
/P
IN
) (%)
V
IN
2.8V TO
4.5V
MAIN DISPLAY
SUB DISPLAY
RGB ILLUMINATOR
MAIN1-4
SUB1-2
SERIAL
INTERFACE
3
RGB
SERIAL PORT
I
MS
I
RGB
4
2
3
RED
GREEN BLUE
3205 TA01a
U
4-LED Main Panel Efficiency
vs Input Voltage
100
90
80
70
60
50
40
30
20
10
FOUR LEDs AT 15mA/LED
(TYP V
F
AT 15mA = 3.2V)
T
A
= 25°C
3.3
3.6
3.9
INPUT VOLTAGE (V)
4.2
3205 TA01b
U
U
0
3.0
3205f
1
LTC3205
ABSOLUTE
(Note 1)
AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
GREEN
MAIN3
MAIN4
SUB1
SUB2
BLUE
STEPUP
ENRGB
V
IN
, DV
CC
, CPO to GND............................. – 0.3V TO 6V
D
IN
, SCLK, LD, STEPUP,
ENRGB ...................................... – 0.3V to (DV
CC
+ 0.3V)
I
CPO
(Note 4)...................................................... 250mA
I
MAIN1-4,
I
SUB1,2
(Note 4) ..................................... 50mA
I
RED,GREEN,BLUE
(Note 4) ..................................... 100mA
I
MS
, I
RGB
(Note 4) .................................................. 1mA
CPO Short-Circuit Duration ............................ Indefinite
Operating Temperature Range (Note 2) .. – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 125°C
ORDER PART
NUMBER
18 RED
17 SGND
24 23 22 21 20 19
MAIN2 1
MAIN1 2
C2
–
C1
–
LTC3205EUF
3
4
25
16 V
IN
15 CPO
14 I
MS
13 I
RGB
C1
+
5
C2
+
6
7
D
IN
8
SCLK
9 10 11 12
LD
DV
CC
UF PART
MARKING
3205
UF PACKAGE
24-LEAD (4mm
×
4mm) PLASTIC QFN
T
JMAX
= 150°C,
θ
JA
= 37°C/W,
θ
JC
= 2°C/W
EXPOSED PAD IS PGND (PIN 25)
MUST BE SOLDERED TO PCB
Consult LTC Marketing for parts specified with wider operating temperature ranges.
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 3.6V, DV
CC
= 1.8V unless otherwise noted.
SYMBOL PARAMETER
Input Power Supply
V
IN
Operating Voltage
DV
CC
Operating Voltage
I
VIN
Operating Current
I
DVCC
Operating Current
V
IN
Shutdown Current
DV
CC
Shutdown Current
White LED Current (MAIN1-MAIN4, SUB1, SUB2)
I
MS
Servo Voltage
Full-Scale LED Current Ratio (I
LED
/I
MS
)
Half-Scale LED Current Ratio (I
LED
/I
MS
)
LED Current Matching
RGB LED Current (RED, GREEN, BLUE)
I
RGB
Servo Voltage
LED Current Ratio (I
LED
/I
RGB
)
RGB PWM Frequency
RGB LED Switching Frequency
RGB PWM (Duty Factor) Range
0/15
3.5
15/15
kHz
%
25µA < I
RGB
< 75µA
q
q
q
ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
2.8
1.5
TYP
MAX
4.5
5.5
UNITS
V
V
µA
mA
I
CPO
, I
MS
, I
IRGB
= 0µA, Step-Down Mode
I
CPO
= 0µA, Step-Up Mode
Serial Port Idle
70
4.2
1
1
1
25µA < I
MS
< 75µA
q
1.193
1.175
368
184
92
1.223
1.223
400
200
100
0.7
1.253
1.271
432
216
108
MAIN1-MAIN4, SUB1, SUB2 Voltage = 1V
MAIN1-MAIN4, SUB1, SUB2 Voltage = 1V
Any Two MAIN or SUB Outputs
q
q
q
mA/mA
mA/mA
mA/mA
%
Quarter-Scale LED Current Ratio (I
LED
/I
MS
) MAIN1-MAIN4, SUB1, SUB2 Voltage = 1V
1.193
1.175
360
1.223
1.223
400
1.253
1.271
440
RED, GREEN, BLUE Voltage = 1V
mA/mA
2
U
µA
µA
µA
V
V
V
V
3205f
W
U
U
W W
W
LTC3205
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 3.6V, DV
CC
= 1.8V unless otherwise noted.
SYMBOL PARAMETER
Charge Pump (CPO)
1:1 Mode Output Impedance
2:3 Mode Output Impedance
CPO Regulation Voltage
CLK Frequency
D
IN
, SCLK, LD, STEPUP, ENRGB
V
IL
V
IH
I
IH
I
IL
t
DS
t
DH
t
L
t
H
t
LW
t
CL
t
LC
Low Level Input Voltage
High Level Input Voltage
Input Current
Input Current
D
IN
Valid to SCLK Setup
D
IN
Valid to SCLK Hold
SCLK Low Time
SCLK High Time
LD Pulse Width
SCLK to LD
LD to SCLK
D
IN
, SCLK, LD, STEPUP, ENRGB = DV
CC
D
IN
, SCLK, LD, STEPUP, ENRGB = 0V
q
q
0.85 • DV
CC
q
q
ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
TYP
0.8
MAX
UNITS
Ω
Ω
V
V
IN
= 3V, V
CPO
= 4.2V (Note 3)
I
CPO
= 20mA, 2:3 Mode
0.6
2.5
4.7
0.8
1.1
0.15 • DV
CC
–1
–1
35
35
35
35
35
35
0
1
1
MHz
V
V
µA
µA
ns
ns
ns
ns
ns
ns
ns
Serial Port Timing
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
The LTC3205E is guaranteed to meet performance specifications
from 0°C to 70°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls.
Note 3:
2:3 mode output impedance is defined as (1.5V
IN
– V
CPO
)/I
CPO
.
Note 4:
Based on long term current density limitations.
TYPICAL PERFOR A CE CHARACTERISTICS
LED Pin Sink Current
vs LED Pin Voltage
V
IN
AC COUPLED
(20mV/DIV)
V
OUT
AC COUPLED
(50mV/DIV)
I
LED
3mA/DIV
(100%
SETTING)
EFFICIENCY (P
LED
/P
IN
) (%)
0mA
200mV/DIV
3205 G01
U W
Input and Output
Charge Pump Noise
100
90
80
70
60
50
40
30
20
10
4-LED Main Panel Efficiency
vs Input Voltage
I
CPO
= 150mA
500ns/DIV
V
IN
= 3.6V
C
IN
= C
CPO
= 0.7µF
3205 G02
0
3.0
FOUR LEDs AT 15mA/LED
(TYP V
F
AT 15mA = 3.2V)
T
A
= 25°C
3.3
3.6
3.9
INPUT VOLTAGE (V)
4.2
3205 TA01b
3205f
3
LTC3205
TYPICAL PERFOR A CE CHARACTERISTICS
1:1 Mode Switch Resistance
vs Temperature
1.0
3.2
I
CPO
= 100mA
OUTPUT RESISTANCE (Ω)
V
IN
= 3.3V
SWITCH RESISTANCE (Ω)
0.9
V
IN
= 3.6V
0.8
V
IN
= 3.9V
2.8
2.6
2.4
2.2
CPO VOLTAGE (V)
0.7
0.6
–40
–15
35
10
TEMPERATURE (°C)
2:3 Mode CPO Voltage in
Current Limit
5.0
4.5
4.0
900
1000
DV
CC
SHUTDOWN CURRENT (µA)
CPO VOLTAGE (V)
FREQUENCY (kHz)
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
0
V
IN
= 4.2V
T
A
= 25°C
100
200
400
300
LOAD CURRENT (mA)
500
600
3205 G13
V
IN
Shutdown Current
vs Input Voltage
1.0
DV
CC
= V
IN
V
IN
SHUTDOWN CURRENT (µA)
0.8
T
A
= 25°C
T
A
= –40°C
0.6
T
A
= 85°C
0.4
80
90
SUPPLY CURRENT (mA)
SUPPLY CURRENT (µA)
0.2
0
2.7
3.0
4.2
3.3
3.6
3.9
V
IN
INPUT VOLTAGE (V)
4
U W
60
3205 G04
3205 G09
2:3 Mode Charge Pump Open-
Loop Output Resistance vs
Temperature (3/2V
IN
– V
CPO
)/I
CPO
3.0
V
IN
= 3V
V
CPO
= 4.2V
C
IN
= C
CPO
= C
FLY1
= C
FLY2
= 1µF
2:3 Mode CPO Voltage
vs Load Current
4.8
4.7
4.6
4.5
4.4
4.3
4.2
4.1
4.0
3.9
V
IN
= 3.1V
V
IN
= 3.2V
V
IN
= 3.3V
V
IN
= 3.4V
V
IN
= 3.0V
0
50
150
200
100
LOAD CURRENT (mA)
250
3205 G06
T
A
= 25°C
V
IN
= 3.6V V
IN
= 3.5V
85
2.0
–40
–15
10
35
TEMPERATURE (°C)
60
85
3205 G05
3.8
Oscillator Frequency
vs V
IN
Voltage
0.5
DV
CC
Shutdown Current
vs DV
CC
V
IN
= DV
CC
T
A
= 25°C
T
A
= –40°C
0.4
0.3
T
A
= 25°C
T
A
= –40°C
800
T
A
= 85°C
700
0.2
T
A
= 85°C
0.1
600
2.7
3.0
3.3
3.6
3.9
V
IN
VOLTAGE (V)
4.2
4.5
3205 G07
0
2.7
3.0
3.3
3.6
3.9
DV
CC
VOLTAGE (V)
4.2
4.5
3205 G08
1:1 Mode No Load Supply Current
vs V
IN
T
A
= 25°C
I
MS
= I
RGB
= 0µA
10
2:3 Mode Supply Current
vs I
CPO
(I
IN
– 3/2I
CPO
)
V
IN
= 3.6V
9 T
A
= 25°C
8
7
6
5
4
3
2
1
70
60
4.5
50
2.7
3
3.3
3.6
3.9
INPUT VOLTAGE (V)
4.2
4.5
3205 G12
0
0
100
50
150
LOAD CURRRENT (mA)
200
3205 G10
3205f
LTC3205
TYPICAL PERFOR A CE CHARACTERISTICS
Input Supply Voltage Required for
Higher LED Currents
3.9
3.7
INPUT VOLTAGE (V)
LED CURRENT (mA)
T
A
= 25°C
3.5
3.3
3.1
2.9
2.7
2.5
25
50
I
MS
I
RGB
100 125 175 200 225 250
I
MS
OR I
RGB
CURRENT (µA)
3205 G14
75
PI FU CTIO S
MAIN1-MAIN4 (Pins 2, 1, 24, 23):
Current Source
Outputs for the Main Display White LEDs. The current for
the main display is controlled by the resistor on the I
MS
pin. The LEDs on the main display can be set to 100%,
50%, 25% or 0% of full-scale programmed current under
software control. See Tables 1 and 2.
5, 4, 6, 3):
Charge Pump Flying
Capacitor Pins. A 1µF X7R or X5R ceramic capacitor should be
connected from C1
+
to C1
–
and another from C2
+
to C2
–
.
D
IN
(Pin 7):
Input Data for the 16-Bit Serial Port. Serial data
is shifted in one bit per clock to control the LTC3205 (see
Table 1). The logic level for D
IN
is referenced to DV
CC
.
SCLK (Pin 8):
Clock Input for the 16-Bit Serial Port (see
Figure 3). The logic level for SCLK is referenced to DV
CC
.
LD (Pin 9):
Load Input for the 16-Bit Serial Port. Command
data is loaded into the command latch on the falling edge
of LD (see Figure 3). The logic level for LD is referenced to
DV
CC
.
ENRGB (Pin 10):
This pin is used to enable and disable the
red, green and blue current sources. Once ENRGB is brought
high, the LTC3205 illuminates the RGB display with the color
combination that was previously programmed via the serial
port. When the main and sub displays are off and ENRGB is
low, the LTC3205 will be in shutdown. The logic level for
ENRGB is referenced to DV
CC
.
C1
+
,
C1
–
,
C2
+
,
C2
–
(Pins
STEPUP (Pin 11):
A logic high on this pin forces the
LTC3205’s charge pump to operate in 2:3 step-up mode,
thereby eliminating any possibility of the device switching
from 1:1 mode to 2:3 mode during critical communication
periods. The logic level for STEPUP is referenced to DV
CC
.
DV
CC
(Pin 12):
This pin sets the logic reference level of the
LTC3205.
I
RGB
(Pin 13):
This pin controls the amount of LED current
at the RED, GREEN and BLUE LED pins. The I
RGB
pin
servos to 1.223V when there is a resistor to ground. The
current in the RED, GREEN and BLUE LEDs will be 400
times the current at the I
RGB
pin when programmed to full
scale (see Tables 1 and 3).
I
MS
(Pin 14):
This pin controls the maximum amount of
LED current in both the main and sub LED displays. The
I
MS
pin servos to 1.223V when there is a resistor to
ground. The currents in the main and sub display LEDs will
be 100, 200 or 400 times the current at the I
MS
pin
depending on which setting is chosen from the serial port.
CPO (Pin 15):
Output of the Charge Pump. This output
should be used to power white, blue and “true” green
LEDs. Red LEDs can be powered from V
IN
or CPO. An X5R
or X7R low impedance (ceramic) 1µF charge storage
capacitor is required on CPO.
3205f
U W
Compliance Voltage for Higher
LED Currents
120
100
80
60
40
20
0
0
0.2
0.4
0.6
0.8
LED PIN VOLTAGE (V)
1.0
3205 G15
RGB LED Turn On and Off
Characteristics
V
IN
= 3.6V
T
A
= 25°C
I
RGB
= 250µA
I
RGB
= 200µA
I
RGB
= 150µA
I
RGB
= 100µA
0mA
I
RGB
= 50µA
5µs/DIV
3205 G011
I
LED
3mA/DIV
U
U
U
5
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