ETC EUP2796

芯美电子
EUP2796
Dual-Display White LED Driver with 3/2X
Switched Capacitor Boost
DESCRIPTION
FEATURES
The EUP2796 is a charge-pump based white-LED
driver that is ideal for mobile phone display
backlighting. It can drive up to 6 LEDs in parallel
with up to 20mA through each LED. Regulated
internal current sources deliver excellent current and
brightness matching in all LEDs. The LED-driver
current sources are split into two independently
controlled groups.
The primary group (4 LEDs) can be used to backlight
the main phone display. The second group (2 LEDs)
can be used to backlight a secondary display or to
provide other lighting features (keypad LEDs, for
example). Brightness of the two groups can be adjusted
independently with pulse-width modulated (PWM )
digital signals.
The EUP2796 works off an extended Li-Ion input
voltage range (2.7V to 5.5V). Voltage boost is
achieved with a high-efficiency 3/2- gain charge pump.
The EUP2796 is available in a 16-pin TQFN package.
z
z
z
z
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Drives up to 6 LEDs with up to 20mA each
LEDs controlled in 2 Distinct Groups, for
Backlighting 2 Displays (main LCD and
sub-LCD)
Excellent Current and Brightness Matching
High Efficiency 3/2X Charge Pump
Extended Li-Ion Input: 2.7V to 5.5V
PWM Brightness Control: 100Hz - 1kHz
3mm × 3mm TQFN-16 Package
RoHS Compliant and 100% Lead(Pb)-Free
APPLICATIONS
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z
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Mobile Phone Display Lighting
Mobile Phone Keypad Lighting
PDAs
General LED Lighting
Typical Application Circuit
Figure 1.
DS2796
Ver1.0
Feb. 2007
1
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EUP2796
Pin Configurations
Package
Type
Pin
Configurations
TQFN-16
Pin Description
PIN
C2P
POUT
Pin
1
2
ISET
3
ENS
4
ENM
5
LED1-6
GND
C1N
VIN
C2N
C1P
11,10,9,8,7,6
12
13
14
15
16
DS2796
Ver1.0
Feb. 2007
DESCRIPTION
Positive terminal of C2
Charge pump output
Current sense input. Connect 1% resistor to ground to set constant current through
LED
Enable for Group-B LEDs (D5~D6). Logic input High=Group-B LEDs ON.
Low=GroupB LEDs OFF. Pulsing this pin with a PWM signal (100Hz-1kHz) can
be used to dim LEDs.
Enable for Group-A LEDs (D1~D4). Logic input High=Group-A LEDs ON.
Low=GroupA LEDs OFF. Pulsing this pin with a PWM signal (100Hz-1kHz) can be
used to dim LEDs.
Current source outputs. Connect directly to LED
Power supply ground input
Negative terminal of C1
Power supply voltage input
Negative terminal of C2
Positive terminal of C1
2
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芯美电子
EUP2796
Ordering Information
Order Number
Package Type
Marking
Operating Temperature range
EUP2796JIR1
TQFN-16
xxxx
2796A
-40 °C to 85°C
EUP2796- □ □ □ □
Lead Free Code
1: Lead Free 0: Lead
Packing
R: Tape & Reel
Operating temperature range
I: Industry Standard
Package Type
J: TQFN-16
Block Diagram
Figure 2.
DS2796
Ver1.0
Feb. 2007
3
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芯美电子
EUP2796
Absolute Maximum Ratings
„
„
„
„
„
„
„
„
„
VIN -------------------------------------------------------------------------------- -0.3V to 6V max
ENM,ENS, ------------------------------------------------------- -0.3V to (VIN+0.3V) w/ 6V max
Continuous Power Dissipation ------------------------------------------------- Internally Limited
TQFN-16L 3 × 3, θJA ------------------------------------------------------------------------- 68°C/W
Junction-to-Ambient Thermal resistance (θJA) ------------------------------------------ 100°C/W
Junction Temperature (TJ-MAX) --------------------------------------------------------------- 150°C
Storage Temperature Range ----------------------------------------------------- -65°C to 150°C
Lead Temp (Soldering, 10sec) --------------------------------------------------------------- 265°C
ESD Rating
Human Body Model ----------------------------------------------------------------------------- 2kV
Operating Conditions
„
„
Input Voltage (VIN) ------------------------------------------------------------------ 2.7V to 5.5V
Ambient Temperature (TA) --------------------------------------------------------- -40°C to 85°C
Electrical Characteristics
Limits in standard typeface and typical values apply for TJ = 25°C. Limits in boldface type apply over the full
operating junction temperature range (-40˚C ≤ TJ≤ 85˚C) . Unless otherwise specified: VIN=3.6V; VDX = 3.4V;
V(EN) = 2.0V; Group A and Group B LEDs not ON simultaneously (ENM = ENS=VIN ); RSET = 7.5kΩ; CIN,
C1,C2, and CPOUT = 1µF.
Symbol
IDX
ID-MATCH
IQ
ISD
VSET
IDX / ISET
ROUT
VHR
fSW
tSTART
VIL
VIH
ILEAK
Parameter
Output Current Regulation
Conditions
3.0V ≤ VIN ≤ 4.2V, and VIN = 5.5V
2.5V ≤ VDX ≤ 3.4V ;RSET=7.5kΩ
3.0V ≤ VIN ≤ 5.5V,
2.5V ≤ VDX ≤ 3.4V ;RSET=11.8kΩ
3.0V ≤ VIN ≤ 5.5V,
2.5V ≤ VDX ≤ 3.4V ;RSET=7.5kΩ
2.7V ≤ VIN ≤ 3.0V,
2.5V ≤ VDX ≤ 3.4V ;RSET=5.8kΩ
Current Matching Between Any Two
VIN =3.0V
Group A Outputs or Group B Outputs
2.7V ≤ VIN ≤ 4.2V, No Load Current,
Quiescent Supply Current
ENM=ENS=OFF
Shutdown Supply Current
2.7V ≤ VIN ≤ 5.5V, EN=OFF
ISET Pin Voltage
2.7V ≤ VIN ≤ 5.5V
Output Current to Current Set Ratio
Charge Pump Output Resistance
VIN =3.0V
IDX=95% × IDX (nom) RSET=7.5kΩ
(IDX (nom) ≈ 15mA)
Current Source Headroom
Voltage Requirement
IDX=95% × IDX (nom) RSET=11.8kΩ
(IDX (nom) ≈ 10mA)
Switching Frequency
3.0V ≤ VIN ≤ 4.2V
Start-up Time
IDX=90% ISET
SD Input Logic Low
2.7V ≤ VIN ≤ 5.5V
SD Input Logic High
2.7V ≤ VIN ≤ 5.5V
Input Leakage Current
VENX= 0V
DS2796
Ver1.0
Feb. 2007
EUP2796
Min
Typ
Max.
14.3
(-8%)
15.5
Unit
16.8
mA(%)
(+8%)
10
15
mA
20
± 0.3
%
4
7.5
mA
0.1
1.18
100
3.5
1
µA
V
Ω
300
mV
200
500
kHz
0.5
1.1
0.1
4
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V
V
µA
芯美电子
EUP2796
Typical Operating Characteristics
Vset vs Power Supply
LED Current vs VIN
1.20
16.25
1.19
15.75
Vset Voltage
LED Current (mA)
16.00
15.50
15.25
1.18
1.17
15.00
14.75
TA=25℃
1.16
14.50
2.7
3.2
3.7
4.2
4.7
5.2
2.7
5.7
3.2
3.7
4.2
4.7
5.2
5.7
Pow er Supply (V)
Pow er Supply (V)
Head Room Voltage vs LED Current
LED Current vs RSET
20.00
30.00
LED Current (mA)
LED Current (mA)
25.00
20.00
15.00
10.00
15.00
10.00
5.00
5.00
0.00
0.00
20
40
60
80
0
100
0.2
0.3
0.4
0.5
Head Room Voltage
Efficient vs Supply Voltage
Driving Six WLEDs (Rset=7.5KΩ, VLED=3.6V)
Input Current vs. Supply Voltage
Driving Six WLEDs (Rset=7.5KΩ, VLED=3.6V）
100
160
90
150
80
70
60
50
40
30
140
130
120
110
100
90
80
20
2.7
3.1
3.5
3.9
4.3
2.7
4.7
Ver1.0
Feb. 2007
3.1
3.5
3.9
4.3
Supply Voltage(V)
Supply Voltage(V)
DS2796
0.1
RSET Resistance (kΩ)
Input Current (mA)
Efficiency (%)
0
5
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4.7
芯美电子
EUP2796
Input Current vs. Supply Voltage
(Rset=7.5KΩ, VLED=3.6V）
LED Current Matching vs. Supply Voltage
(Rset=7.5KΩ,VLED=3.6V)
16.25
160
6 LEDs
16.00
4 LEDs
120
LED Current (mA)
Input Current (mA)
140
2 LEDs
100
80
60
15.50
15.25
15.00
14.75
40
14.50
20
2.7
3.1
3.5
3.9
4.3
2.7
4.7
Ver1.0
Feb. 2007
3.1
3.5
3.9
4.3
Supply Voltage(V)
Supply Voltage(V)
DS2796
15.75
6
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4.7
芯美电子
EUP2796
Application Information
Enable Pins: ENM, ENS
The EUP2796 has 2 enable pins-ENM and ENS,
which control the main and sub LEDs. All two are
active-high logic (HIGH = ON). When both of ENM
or ENS voltage is low (<0.5V), the part is in
shutdown mode. All internal circuitry is OFF and the
part consumes almost no supply current when the
EUP2796 is shutdown. When the voltage on either of
ENM and ENS pin is high (>1.1V), the part is active.
The charge pump is ON, and turn on the output
currents to drive the LEDs. ENM activates
/deactivates the four group-A outputs (D1-D4). ENS
activates/deactivates the two group-B outputs
(D5-D6).
There is no pull down resistors that are connected
internally between each of the enable pins to ground.
Maximum Output Current, Maximum LED
Voltage, Minimum Input Voltage
The EUP2796 can drive 6 LEDs at 15mA each from
an input voltage as low as 3.0V, so long as the LEDs
have a forward voltage of 3.6V or less (room
temperature).
The statement above is a simple example of the LED
drive capabilities of the EUP2796. The statement
contains the key application parameters that are
required to validate an LED- drive design using the
EUP2796: LED current (ILED), number of active
LEDs (N), LED forward voltage (VLED), and minimum input voltage (VIN-MIN).
The equation below can be used to estimate the total
output current capability of the EUP2796:
1.5 ∗ VIN − VLED
, (eq.1)
N ∗ R OUT + K HR
1.5 ∗ VIN − VLED
I LED _ MAX =
N ∗ 4Ω + 12mV / mA
Setting LED Currents
The output currents of the EUP2796 can be set to a
desired value simply by connecting an appropriately
sized resistor (RSET) between the ISET pin of the
EUP2796 and GND. The output currents (LED
currents) are proportional to the current that flows out
of the ISET pin. The output currents are a factor of 100
greater than the ISET current. The feedback loop of an
internal amplifier sets the voltage of the ISET pin to
1.18V(typ.). Placing a resistor between ISET and GND
programs the ISET current, and thus the LED currents.
The statements above are simplified in the equations
below:
I LED _ MAX =
ROUT – Output resistance. This parameter models the
internal losses of the charge pump that result in
voltage droop at the pump output POUT. Since the
magnitude of the voltage droop is proportional to the
total output current of the charge pump, the loss
parameter is modeled as a resistance. The output
resistance of the EUP2796 is typically 4Ω (VIN = 3.0V,
TA = 25˚C). In equation form:
I DXX = 100 × (VSET × R SET )
VPOUT = 1.5 × VIN − N × I LED × R OUT (eq.2 )
R SET = 100 × (1.18V × I DXX )
KHR – Headroom constant. This parameter models the
minimum voltage required to be present across the
current sources for them to regulate properly. This
minimum voltage is proportional to the programmed
LED current, so the constant has units of mV/mA.
The typical KHR of the EUP2796 is 12mV/mA. In
equation form:
(VPOUT − VLED ) > K HR × I LED (eq.3)
The "ILED-MAX" equation (eq. 1) is obtained from
combining the ROUT equation (eq. 2) with the KHR
equation (eq. 3) and solving for ILED. Maximum LED
current is highly dependent on minimum input
voltage and LED forward voltage. Output current
capability can be increased by raising the minimum
input voltage of the application, or by selecting an
LED with a lower forward voltage. Excessive power
dissipation may also limit output current capability of
an application.
DS2796
Ver1.0
Feb. 2007
7
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EUP2796
This inrush current results in a current and voltage
spike at the input of the part. By only applying the
PWM signal to ENM/ENS, the charge pump stays on
continuously and much lower input noise results.
In cases where a PWM signal must be connected to
the EN pin, measures can be taken to reduce the
magnitude of the charge-pump turn-on voltage spikes.
More input capacitance, series resistors and/or ferrite
beads may provide benefits.
Soft-Start
The EUP2796 contains internal soft-start circuitry to
limit input inrush currents when the part is enabled.
Soft start is implemented internally with a
controlled turn-on of the internal voltage reference.
During soft start, the current through the LED outputs
rise at the rate of the reference voltage ramp. Due to
the soft-start circuitry, turn-on time of the EUP2796 is
approximately 100µs (typ.).
Thermal Protection
Internal thermal protection circuitry disables the
EUP2796 when the junction temperature exceeds
160˚C (typ.). This feature protects the device from
being damaged by high die temperatures that might
otherwise result from excessive power dissipation.
The device will recover and operate normally when
the junction temperature falls below 140˚C (typ.).It is
important that the board layout provides good thermal
conduction. This will help to keep the junction
temperature within specified operating ratings.
Capacitor Selection
The EUP2796 requires 4 external capacitors for
proper operation. Surface-mount multi-layer ceramic
capacitors are recommended. These capacitors are
small, inexpensive and have very low equivalent
series resistance (ESR<20mΩ typ.). Tantalum
capacitors, OS-CON capacitors, and aluminum
electrolytic capacitors are not recommended for use
with the EUP2796 due to their high ESR, as
compared to ceramic capacitors.
For most applications, ceramic capacitors with X7R
or X5R temperature characteristic are preferred for
use with the EUP2796. These capacitors have tight
capacitance tolerance (as good as ±10%) and hold
their value over temperature (X7R: ±15% over -55˚C
to 125˚C; X5R: ±15% over -55˚C to 85˚C).
Capacitors
with
Y5V
or
Z5Utemperature
characteristic are generally not recommended for
use with the EUP2796. Capacitors with these
temperature characteristics typically have wide
capacitance tolerance (80%,-20%) and vary
significantly over temperature (Y5V: 22%, -82% over
-30˚C to 85˚C range; Z5U: 22%, -56% over 10˚C to
85˚C range). Under some conditions, a nominal 1µF
Y5V or Z5U capacitor could have a capacitance of
only 0.1µF. Such detrimental deviation is likely to
cause Y5V and Z5U capacitors to fail to meet the
minimum capacitance requirements of the EUP2796.
For LED driver applications, the input voltage ripple
is more important than output ripple. Input ripple is
controlled by input capacitor CIN, increasing the
value of input capacitance can further reduce the
ripple. Practically, the input voltage ripple depends on
the power supply’s impedance. If a single input
capacitor CIN cannot satisfy the requirement of
application, it is necessary to add a low-pass filter.
Adjusting LED Brightness (PWM control)
Perceived LED brightness can be adjusted using a
PWM control signal to turn the EUP2796 current
sources ON and OFF at a rate faster than perceptible
by the eye. When this is done, the total brightness
perceived is proportional to the duty cycle (D) of the
PWM signal (D = the percentage of time that the LED
is on in every PWM cycle). A simple example: if the
LEDs are driven at 15mA each with a PWM signal
that has a 50% duty cycle, perceived LED brightness
will be about half as bright as compared to when the
LEDs are driven continuously with 15mA. A PWM
signal thus provides brightness (dimming) control for
the solution.
The minimum recommended PWM frequency is
100Hz. Frequencies below this may be visibly
noticeable as flicker or blinking. The maximum
recommended PWM frequency is 1kHz. Frequencies
above this may cause interference with internal
current driver circuitry.
The preferred method for applying a PWM signal to
adjust brightness is to keep the master EN voltage ON
continuously and to apply the PWM signal(s) to the
current source enable pin(s): ENM and/or ENS. The
benefit of this type of connection can be best
understood with a contrary example. When a PWM
signal is connected to the master enable (EN) pin, the
charge pump repeatedly turns on and off. Every time
the charge pump turns on, there is an inrush of
current as capacitances, both internal and external, are
recharged.
DS2796
Ver1.0
Feb. 2007
8
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EUP2796
Packaging Information
TQFN-16
SYMBOLS
A
A1
b
E
D
D1
E1
e
L
DS2796
Ver1.0
Feb. 2007
MILLIMETERS
MIN.
MAX.
0.70
0.80
0.00
0.05
0.18
0.30
2.90
3.10
2.90
3.10
1.70
1.70
0.50
0.30
0.50
INCHES
MIN.
MAX.
0.028
0.031
0.000
0.002
0.007
0.012
0.114
0.122
0.114
0.122
0.067
0.067
0.020
0.012
0.020
9
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