XRP6840
4.3A Supercapacitor Flash LED Driver with I2C
December 2009
Rev. 1.0.0
GENERAL DESCRIPTION
EVALUATION BOARD MANUAL
The XRP6840 is a controlled-current dual-cell
supercapacitor charger and high power LED
driver. Operating from a standard lithium-ion
battery, the XRP6840 provides up to 4.3A of
programmable Flash LED current and up to
600mA
and
5.6V
of
programmable
supercapacitor charging current and voltage.
The XRP6840EVB, Exar’s XRP6840 Evaluation
Board, supports either XRP6840A or XRP6840B
in a 4x4 TQFN package and is fitted by default
with the XRP6840A supporting three channels.
With 1x, 1.5x and 2x charge pump operating
modes, XRP6840EVB can provide a stable drive
current for up to 3 1.5A, 4W Luxeon Flash LEDs.
The evaluation board is a completely assembled
and tested surface mount board which provides
easy probe access points to all XRP6840 inputs
and outputs for easy connection and
measuring.
FEATURES
Programmable 4.3A Flash LED Driver
Torch and Flash Modes
Programmable Supercapacitor Charger
600mA Adjustable Charging Current
Programmable Supercapacitor Voltage
Active Voltage Balance Control
The Evaluation Board schematic diagram is
shown in Figure 1.
Tri-mode Charge Pump Architecture
1x, 1.5x, 2x Operation Modes
2.4MHz Switching Frequency
I2C Serial Interface
EVALUATION BOARD SCHEMATICS
16
18
17
C2N
C2P
GND
SDA
NC
PGND
Vin
PGND
R7
NP
15
Flash Ready Indicator
13
C3
CAPxx
12
11
D3
LED
J3
10
9
R3
0.1
J4_LED3
R9
3k
D4
J2
D2
LED
J1
R2
0.1
D1
LED
R1
0.1
FLASH
RDY
RDY
J7
14
1M
8
R8
U1
XRP6840
SCL
6
J5
1
2
3
CAP
FLASH
5
COUT
10uF
U1
RDY
LED3
4
VOUT
VOUT
LED2
3
C1P
20
VIN
2
CGND
LED1
R5
1 NP
2
3
4
RDY
7
J6
R4
NP
RESET_N
1
C1N
CIN
22uF
Vin
19
C2
C1
0.47uF 0.47uF
VIN: 2.7-5.5V
J4_LED2
J4_LED1
SW PUSHBUTTON
R6
Vin
SW1
FLASH
10K
FLASH
Fig. 1: XRP6840 Evaluation Board Schematics
Exar Corporation
48720 Kato Road, Fremont CA 94538, USA
www.exar.com
Tel. +1 510 668-7000 – Fax. +1 510 668-7001
XRP6840
4.3A Supercapacitor Flash LED Driver with I2C
PIN ASSIGNEMENT
XRP6840A – 3 Channel Version
XRP6840B – 2 Channel Version
Fig. 2: XRP6840 Pin Assignment
PIN DESCRIPTION
Name
Pin Number
CGND
1
Charge pump ground pin.
RDY
2
Active high push-pull output. RDY is high when VOUT reached to 100mV below its
VOUT_LIMIT voltage. The VOUT_LIMIT for Flash mode is determined by STATUS2 register [B7
B6 B5]. The VOUT_LIMIT for Torch mode is 4.50V.
SCL, SDA
3, 4
The SDA and SCL pins connect to the I2C bus. Multiple functions can be programmed
through his interface. They can also be used for read-back.
PGND
5, 11
RESET_N
6
LED1, LED2, LED3
(XRP6840A)
7, 8, 9
LED1, NC, LED2
(XRP6840B)
7, 8, 9
Description
Power ground pin. The Source of internal NMOS is connected to this pin.
Active Low input pin.
If RESET_N = 0, then XRP6840 is in Shut-down mode
If RESET_N = 0 and STATUS1 register [B5] = 0, then reset all registers to logic low.
If RESET_N = 0 and STATUS1 register [B5] = 1, then all bits of all registers will be
saved.
LED1, LED2, LED3 connect to the drain of the internal NMOS which are current sources
for LED current. These current sources are controlled by LEDFLASH or LEDTORCH
registers which is programmed through I2C to provide the Torch and Flash current for
the LEDs. LED1, LED2, LED3 pins can be connected together to provide higher LED
current. If a pin is not used connect it to VOUT. The XRP6840 incorporates a short LED
protection circuit which shut-down LED current if LED voltage approaches to VOUT_LIMIT.
FLASH
10
Digital Input pin. Active high. If STATUS1 register [B7 B6] = 11 and FLASH = 1 then
LEDs are ON for one Flash timeout duration. Flash Timeout duration is controlled by
STATUS1 register [B1 B0].
NC
12
No connection. This pin can be connected to PGND pin for heat sink.
GND
13
Ground pin. This ground pin doesn’t carry high internal current.
CAP
14
This pin is the output of an internal Op-Amp. This internal Op-Amp is powered by VOUT.
The output voltage is half of VOUT, and output resistance is 470Ω. The sink and source
current is limited by 470Ω output resistance. This provides active balancing between
two internal sections of the super capacitor.
VOUT
15
Output voltage. Connect positive terminal of SuperCap here. Connect the LEDs
between this pin and the corresponding internal current source. Decouple with 10µF
ceramic capacitor close to the pins of the IC.
C2P, C2N
16, 17
Connect C2 external flying capacitor between these pins.
C1P, C2P
18, 19
Connect C1 external flying capacitor between these pins.
VIN
20
Thermal Pad
-
© 2009 Exar Corporation
Power supply input. Decouple with 10µF ceramic capacitor close to the pins of the IC.
Connect thermal pad to PGND pins.
2/8
Rev. 1.0.0
XRP6840
4.3A Supercapacitor Flash LED Driver with I2C
USING THE EVALUATION BOARD
Address
The XRP6840 Evaluation Board can be powered
from a 5V power supply. Connect with short
leads directly to the “VIN” and “GND” posts. To
power up XRP6840A/B connect the “RESET_N”
Jumper to the “VIN” position and connect J7 or
place Resistor R7 of 0. The I2C can be
programmed through SCL, SDA jumper J6.
1
0
1
STATUS2
Flash
Shut
Torch Down
Gain
Mode Control
Flash
Flash Flash
V
V
Ready
LEDFLASH
LED1
LED2
LED3*
LEDTORCH
LED1
LED2
LED3*
STATUS1
POWERING UP THE XRP6840 CIRCUIT
0
Flash
Torch
Mode
Flash
V
0
0
0
R/W
Flash
Flash
Timeout Timeout
Gain
-
UVLO
Fault
Temp
Fault
0
0
D2
D1
D0
-
-
D3
D2
D1
D0
-
Table 1: XRP6840 I C Registers Bit Map
2
* Not used for XRP6840B
STATUS1 Register
STATUS1 Register Bits B7, B6, B4 and B3
GETTING STARTED ON XRP6840EVB
B7
B6
B4
B3
1. Connect VIN and GND to a power supply
(VIN range is 2.7V~5.5V).
0
1
0
0
High Efficiency Torch Mode
0
1
0
1
1X Torch Mode
2. Connect RESET_N to VIN on Jumper J5.
0
1
1
0
1.5X Torch Mode
1
1
1
2X Torch Mode
3. Connect Jumper J7 to drive LEDs.
0
1
0
0
0
Auto Gain Torch Mode
4. Connect I2C Interface pins: SDA, SCL, GND
1
0
0
1
1X Torch Mode
0
1
0
5. Program Torch or Flash Mode and the
desired operating current through I2C.
1
1.5X Torch Mode
1
0
1
1
2X Torch Mode
1
1
0
0
Auto Gain Flash Mode
1
1
0
1
1X Flash Mode
1
1
1
0
1.5X Flash Mode
1
1
1
1
2X Flash Mode
6. For Flash Mode, the push button can be
used to power LEDs after each Flash
Duration Timeout.
Table 2: STATUS1 Register Operation Modes
The I2C Interface and the available Registers
are described in the subsequent sections.
STATUS1 Register Bit B5
This bit is used to save or reset the contents of
STATUS1, STATUS2, LEDFLASH and LEDTORCH
registers for the next I2C command when
RESET_N, pin 6, is ‘1’. If B5 is ‘1’ then all bits
in these registers will be saved. Otherwise if B5
is ‘0’ then all bits will be reset to ‘0’.
I2C SERIAL INTERFACE
REGISTERS
The XRP6840 has five serially programmable
data registers via the I²C interface. These
registers can be reset to ‘0’ through power on
reset or setting RESET_N, pin 6, to ‘0’. The first
register is for Device Address as shown in
Figure 3; it is activated by ‘28’ HEX (7-bit
format). The second register, STATUS1,
contains the control word for programming
operating modes, shutdown control, charge
pump modes and flash timeout. The third
register, STATUS2, contains the flash voltage
level, read back of the Flash Ready, and fault
conditions UVLO and over temperature. The
fourth register, LEDFLASH, controls individual
LED channels and current level in Flash Mode.
The fifth register, LEDTORCH, controls
individual LED channels and current level in
Torch Mode.
Register
B7
B6
B5
© 2009 Exar Corporation
B4
B3
B2
B1
Operation Mode
STATUS1 Register Bits B1 and B0
These two bits program the flash timeout
duration as follows:
B1
B0
Flash Duration
0
0
1
1
0
1
0
1
0.11s
0.22s
0.53s
1.10s
Table 3: Charge Pump Mode Selection
STATUS2 Register
Flash Mode Voltage Programming
VOUT_LIMIT in Flash Mode is regulated with 50mV
of hysteresis and is programmed through bits
B7, B6 and B5 of STATUS2 register as follows:
B0
3/8
Rev. 1.0.0
XRP6840
4.3A Supercapacitor Flash LED Driver with I2C
B7
B6
B5
Comment
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
4.55V
4.70V
4.85V
5.00V
5.15V
5.30V
5.45V
5.60V
are used to set the torch LED current levels in
each channel. Table 6 provides the DAC codes
and their corresponding nominal current levels
for each channel. Remember that the total
current that can be supported in torch mode is
600mA divided by the gain of the charge pump.
If 2 channels are set to 440mA (a total of
880mA), even with a gain of 1X, the input
current limit will clamp the total current to
approximately 600mA.
Table 4: Flash Mode VOUT_LIMIT Settings
Bit B4
RDY bit is available for I2C read-back. This bit
is set to ‘1’ when VOUT > VOUT_LIMIT, and set to ‘0’
otherwise.
D3-D0
Code
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
Fault mode read-back bits B3, B2
These bits are designed for 2 Fault Mode flags
and are also available for I2C read-back. Bits 3
and 2 are set to ‘1’ when UVLO and over
temperature conditions are detected, as shown
in Table 1.
LEDFLASH Register
LEDFLASH register, bits B7, B6 and B5 are used
to activate the LED outputs channels as
summarized in Table 1; they correspond to
LED1, LED2 and LED3. Bits B4, B3 and B2
represent the DAC codes D2, D1, D0. They are
used to set the flash LED current levels in each
channel. Table 5 provides the DAC codes and
the corresponding nominal current levels for
each channel:
D2-D0
Code
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
XRP6840A
IOUT/Ch. (mA)
0
400
586
770
948
1197
1291
1445
D2-D0
Code
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
XRP6840A
IOUT/Ch. (mA)
0
23
46
66
86
105
125
145
165
185
205
225
245
260
280
300
D3-D0
Code
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
XRP6840B
IOUT/Ch. (mA)
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
34
66
97
127
155
185
215
245
275
305
330
360
385
415
440
Table 6: Torch Mode Output Current
Addressing and Writing Data
To write data to the XRP6840 one of the
following two sequences is required:
Easy shutdown/startup sequence
[Slave Address with write bit][Data for Status]
XRP6840B
IOUT/Ch. (mA)
Full shutdown/startup sequence
0
597
875
1127
1400
1671
1910
2150
[Slave Address with write bit][Data for Status]
[Data for LEDFLASH][Data for LEDTORCH]
Slave address is ‘28’ Hex.
Addressing and Reading Data
Table 5: Nominal Flash Mode Output Current
To read data from the XRP6840 the following
sequence is required:
LEDTORCH Register
[Slave Address with read bit][Data for Status]
[Data for LEDFLASH][Data for LEDTORCH]
LEDTORCH register bits B2 to B7, also
summarized in Table 1; they correspond to
LED1, LED2 and LED3. Bits B4, B3, B2, and B1
represent the DAC codes D3, D2, D1, D0. They
TYPICAL PERFORMANCE CHARACTERISTICS
All data taken at VIN = 2.7V-5.5V, unless otherwise specified.
© 2009 Exar Corporation
4/8
Rev. 1.0.0
XRP6840
4.3A Supercapacitor Flash LED Driver with I2C
Fig. 3: High Efficiency Torch Mode ILED at 200mA
with PWF4W-001
Fig. 4: High Efficiency Torch Mode, LED Current versus VIN
Fig. 5: 200mA High Efficiency Torch Mode with 0.55F
Supercap, CH1=VIN, CH2=VOUT, CH3=LEDX,
CH4=IVIN =0.5A/div
Fig. 6: 200mA Torch Mode with 0.55F Supercap, CH1=VIN,
CH2=VOUT, CH3=LEDX, CH4=IVIN =0.5A/div
Fig. 7: LED Current Settling Time: 0mA to 100mA.
Fig. 8: LED Current Settling Time: 100mA to 200mA.
CH1=SDA, CH2=SCL, CH4=ILED=0.1A/div
CH1=SDA, CH2=SCL, CH4=ILED=0.1A/div
© 2009 Exar Corporation
5/8
Rev. 1.0.0
XRP6840
4.3A Supercapacitor Flash LED Driver with I2C
Fig. 9: Figure 21: Flash Mode Enable From Shutdown
CH1=RESET_N, CH2=RDY, CH3=VOUT
© 2009 Exar Corporation
Fig. 10: Flash Mode Shutdown. CH1=RESET_N,
CH2=RDY, CH3=VOUT
6/8
Rev. 1.0.0
XRP6840
4.3A Supercapacitor Flash LED Driver with I2C
EVALUATION BOARD LAYOUT
Fig. 11: XRP6840 Evaluation Board Component Placement
and Component Side Lay Out
Fig. 12: XRP6840 Evaluation Board
Soldier Side Lay Out
Fig. 13: XRP6840 Evaluation Board Component Placement
BILL OF MATERIAL
Ref.
Qty
Manufacturer
Part Number
Size
Component
EVAL BD
1
U1
1
Exar Corp
146-6675-02
2.25”x3.0”
Exar Corp
XRP6840AILB-F
TQFN-20L
1
1
2
Murata
Murata
Murata
GRM219R61A226KE44B
GRM219R61A106KE44B
GRM155B31A474KE14B
0805
0805
0402
C3
1
Cap-xx
HS106
29x17x2.4mm
D1, D2, D3
D4
J1, J2, J3, J7
J4, J5
J6
R1, R2, R3
R4, R5, R7
R6
R8
R9
SW1
Test Point VIN,
VOUT, GND, RDY,
CAP, CIN, FLASH
3
1
4
2
1
3
3
1
1
1
1
Lumileds
Vishay
Wurth Electronics
Wurth Electronics
Wurth Electronics
Vishay
NP
Vishay
Vishay
Vishay
Bourn Inc.
LXCL-PWF4W-0001
TLMG2100-GS08
61303611121
61303611121
61304011021
CRCW0805R100F
NP
CRCW060310K00F
CRCW06031M00J
CRCW06033K01J
7914J-1-000
2.04x1.64x0.75mm
2.3x1.3x1.4mm
0.64mm SQ x 6mm
0.64mm SQ x 6mm
0.64mm SQ x 6mm
0805
NP
0603
0603
0603
4.8x5.0 mm
XRP6840EVB Evaluation Board
4.8A Supercapacitor Flash LED
Driver with I2C
Ceramic 22µF 10V X5R
Ceramic 10µF 10V X5R
Ceramic 0.47µF 10V X5R
Super Capacitor 0.6F/5.5V 70mΩ
ESR, 20%
1.5A Luxeon Flash LED
Green Color Mini LED
2 Pin Header, 2.54mm pitch
3 Pin Header, 2.54mm pitch
4 Pin Angled Header, 2.54mm pitch
0.1Ω Resistor, 0.25W, 1%
NP
10KΩ Resistor, 0.1W, 1%
1MΩ Resistor, 0.1W, 5%
3.01KΩ Resistor, 0.1W, 1%
Push Button Switch
CIN
COUT
C1, C2
12
Mill-Max
0300-115-01-4727100
0.042” diameter
Test Point Female Pin
© 2009 Exar Corporation
7/8
Rev. 1.0.0
XRP6840
4.3A Supercapacitor Flash LED Driver with I2C
REVISION HISTORY
Revision
Date
1.0.0
12/07/09
Initial release of document
Description
09/08/14
OBSOLETE – See “XRP6840EVB Exarizer”
FOR FURTHER ASSISTANCE
Email:
customersupport@exar.com
Exar Technical Documentation:
http://www.exar.com/TechDoc/default.aspx?
EXAR CORPORATION
HEADQUARTERS AND SALES OFFICES
48720 Kato Road
Fremont, CA 94538 – USA
Tel.: +1 (510) 668-7000
Fax: +1 (510) 668-7030
www.exar.com
NOTICE
EXAR Corporation reserves the right to make changes to the products contained in this publication in order to improve design,
performance or reliability. EXAR Corporation assumes no responsibility for the use of any circuits described herein, conveys
no license under any patent or other right, and makes no representation that the circuits are free of patent infringement.
Charts and schedules contained here in are only for illustration purposes and may vary depending upon a user’s specific
application. While the information in this publication has been carefully checked; no responsibility, however, is assumed for
inaccuracies.
EXAR Corporation does not recommend the use of any of its products in life support applications where the failure or
malfunction of the product can reasonably be expected to cause failure of the life support system or to significantly affect its
safety or effectiveness. Products are not authorized for use in such applications unless EXAR Corporation receives, in writing,
assurances to its satisfaction that: (a) the risk of injury or damage has been minimized; (b) the user assumes all such risks;
(c) potential liability of EXAR Corporation is adequately protected under the circumstances.
Reproduction, in part or whole, without the prior written consent of EXAR Corporation is prohibited.
© 2009 Exar Corporation
8/8
Rev. 1.0.0
工商网监
湘ICP备2023018690号
