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PDF EMD2794-00BA16GRR Data sheet ( Hoja de datos )
| Número de pieza | EMD2794-00BA16GRR | |
| Descripción | Regulated Switched Capacitor LED Current Source | |
| Fabricantes | Elite MicroPower | |
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Elite MicroPower Inc.
Preliminary EMD2794/EMD2795
Regulated Switched Capacitor LED Current
Source with Analog and PWM Brightness Control
General Description
The EMD2794/EMD2795 is a 1.5x/1.0x charge pump that
provides four regulated current sources. It accepts an
input voltage range from 2.7V to 5.5V and maintains a
constant current determined by an external resistor.
The EMD2794/EMD2795 delivers up to 80mA of load current
to accommodate four White LEDs. The switching
frequency is fixed at 1.2MHz to make noise filtering easier.
Brightness control can be done by both linear and PWM
techniques. Linear control is achieved by applying 0V to
3.0V to the BRGT pin to linearly vary the LED current. PWM
technique is to apply a clock to the EN pin to having
brightness varying with clock duty.
Shutdown is done by applying low (high for 2795) to the pin
EN. The VIN current drops to less than 1.0uA in shutdown
mode.
The EMD2794/EMD2795 is available in a TQFN-16 & FBP-16
3x3 package.
Features
Regulated current sources with ±0.5% matching
between any two outputs
High efficiency 3/2 boost function
Drives one to four white LEDs.
2.7V to 5.5V input range
Up to 80mA output current
Analog brightness control
Active-low or high shutdown input (‘94/95)
Very small solution size and no inductor
Shutdown Current < 1μA
1.2MHz switching frequency
Constant frequency generates predictable noise
spectrum
QFN16 3x3 package
Applications
White LED Display Backlights
White LED Keypad Backlights
1-Cell Li-Ion battery-operated equipment including
PDAs, hand-held PCs, cellular phones.
Elite MicroPower Inc. reserves the right to make changes to improve reliability or manufacturability without notice, and
customers are advised to obtain the latest version of relevant information prior to placing orders.
DSD2794/2795_V2.1 January 21 th 2008
Page 1 of 14
www.elitemicropower.com
1 page  
Elite MicroPower Inc.
Preliminary EMD2794/EMD2795
Absolute Maximum Ratings (Note 1)
VIN -0.5 to 6.2V
EN -0.5 to 6.2V
BRGT
-0.5 to min[(VIN+0.3), 6.2V]
Continuous Power Dissipation (Note 2) Internally Limited
TJMAX (Note 2)
135oC
Storage Temeprature
-60oC to +150oC
Lead Temp. (Soldering, 5 sec.)
260oC
ESD Rating
Human Body Model
Machine Model
2kV
200V
Recommended Operating Conditions
VIN 2.7 to 5.5V
Ambient Temperature (TA)
-30C to +85C
Junction Temperature (Tj)
-30C to +100C
Electrical Characteristics
Limits in standard typeface are for TJ=25oC and limits in boldface type apply over the full Operating Junction Temperature
Range (-30oC≦TJ≦+100oC). Unless otherwise specified, C1=C2=CIN=COUT=1uF, VIN=3.6V, BRGT pin =0V; RSET=124Ω; EMD2794:
VEN=VIN (EMD2795: VEN=0V).
Symbol
Parameter
Conditions
Min Typ Max Units Note
IDX Available current
3.0V≦VIN≦5.5V
VDX≦3.8V, BRGT=50mV
16.7 mA
ID-MATCH
Current Matching Between Any
Two Outputs
VDX=3.6V
0.5 %
IQ Quiescent Supply Current
3.0V≦VIN≦4.2V, Active, No Load,
RSET=OPEN
3.2 mA
ISD Shutdown Supply Current
3.0V≦VIN≦5.5V, Shutdown
1 uA
IPULL-EN
EN pull-high current (EMD2795)
3.2 uA
VCP 1.5X to 1.0X Threshold
4.75 V
VCPH
1.0X to 1.5X Hysteresis
300 mV
VIH EN Input Logic High (EMD2794)
1.0
EN Input Logic High (EMD2795)
0.8VIN
VIL EN Input Logic Low (EMD2794)
0.4 V
RBRGT
fSW
EN Input Logic Low (EMD2795)
BRGT Input Resistance
Switching Frequency
3.0V≦VIN≦5.5V
0.2VIN
240
1.2
kΩ
MHz
Note 1: Absolute maximum ratings indicate limits beyond which damage to the device may occur. Electrical specifications
do not apply when operating the device beyond its rated operating conditions.
Note 2: Internal thermal shutdown circuitry protects the device from permanent damage. Thermal shutdown engages at
TJ=150°C (typ.) and disengages at TJ=140°C (typ.).
Elite MicroPower Inc. reserves the right to make changes to improve reliability or manufacturability without notice, and
customers are advised to obtain the latest version of relevant information prior to placing orders.
DSD2794/2795_V2.1 January 21 th 2008
Page 5 of 14
www.elitemicropower.com
5 Page 
Elite MicroPower Inc.
Preliminary EMD2794/EMD2795
100% duty cycle will turn off the LEDs and a 50% duty
cycle will result in an average ILED being half the
programmed LED current.
BRGT
0.0V
0.5V
1.0V
1.5V
2.0V
2.5V
3.0V
Table 1 RSET Values
LED Current
5mA
10mA
15mA
376Ω
188Ω
125Ω
761Ω
381Ω
254Ω
1.15kΩ
573Ω
382Ω
1.53kΩ
766Ω
510Ω
1.92kΩ
958Ω
639Ω
2.30Ω
1.15kΩ
767Ω
2.69kΩ 1.34kΩ
895Ω
20mA
94Ω
190Ω
287Ω
383Ω
479Ω
575Ω
672Ω
Brightness Control Using BRGT
1. Choose the maximum ILED desired and determine
the max voltage to be applied to the BRGT pin. For
constant brightness, set BRGT to a fixed voltage
between 0V to 3V.
2. Use the ILED equation above to calculate RSET.
3. Use Table 2 as a reference for the dimming profile of
the LEDs, when BRGT ranges from 0V to 3V.
BRGT
0.0V
0.5V
1.0V
1.5V
2.0V
2.5V
3.0V
Table 2 LED Current
2.67kΩ
LED Current
1.33kΩ
909Ω
0.7mA
1.4mA
2.1mA
1.4mA
2.9mA
4.2mA
2.1mA
4.3mA
6.3mA
2.9mA
5.8mA
8.4mA
3.6mA
7.2mA 10.5mA
4.3mA
8.7mA 12.7mA
5.0mA 10.1mA 14.8mA
665Ω
2.8mA
5.7mA
8.6mA
11.5mA
14.4mA
17.3mA
20.2mA
CHARGE PUMP OUTPUT AND INPUT (POUT AND SOUT)
The EMD2794/5 charge pump is an unregulated switched
capacitor converter with a gain of 1.5. The voltage at the
output of the pump (the POUT pin) is nominally 1.5 x VIN.
This rail can be used to deliver additional current to other
circuitry. Since POUT is unregulated, driving LEDs directly off
POUT is usually practical only with a fixed input voltage. If
the input voltage is not fixed (Li-Ion battery, for example),
using a linear regulator between the POUT pin and the LEDs
is recommended.
LED drivers use power supply from pin SOUT. To maintain
normal operation of LED current output, connect pin SOUT
directly to POUT on PCB.
PARALLEL DX OUTPUTS FOR INCREASED CURRENT DRIVE
Outputs D1 through D4 may be connected together in any
combination to drive higher currents through fewer LEDs.
For example, outputs D1 and D2 can be connected
together to drive one LED while D3 and D4 are connected
together to drive a second LED.
THERMAL PROTECTION
When the junction temperature exceeds 150°C (typ.), the
EMD2794/5 internal thermal protection circuitry disables
the part. This feature protects the device from damage
due to excessive power dissipation. The device will recover
and operate normally when the junction temperature falls
below 140°C (typ.). It is important to have good thermal
conduction with a proper layout to reduce thermal
resistance.
Elite MicroPower Inc. reserves the right to make changes to improve reliability or manufacturability without notice, and
customers are advised to obtain the latest version of relevant information prior to placing orders.
DSD2794/2795_V2.1 January 21 th 2008
Page 11 of 14
www.elitemicropower.com
11 Page | ||
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