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DS4422 Schematic ( PDF Datasheet ) - Maxim Integrated Products

Teilenummer DS4422
Beschreibung (DS4422 / DS4424) 7-Bit Sink/Source Current DAC
Hersteller Maxim Integrated Products
Logo Maxim Integrated Products Logo 




Gesamt 10 Seiten
DS4422 Datasheet, Funktion
Rev 0; 3/08
Two-/Four-Channel, I2C, 7-Bit Sink/Source
Current DAC
General Description
The DS4422 and DS4424 contain two or four I2C pro-
grammable current DACs that are each capable of
sinking and sourcing current up to 200µA. Each DAC
output has 127 sink and 127 source settings that are
programmed using the I2C interface. The current DAC
outputs power up in a high-impedance state.
www.DataSheet4U.com
Applications
Power-Supply Adjustment
Power-Supply Margining
Adjustable Current Sink or Source
Ordering Information
PART
OUTPUTS TEMP RANGE
DS4422N+
2 -40°C to +85°C
DS4422N+T&R
2 -40°C to +85°C
DS4424N+
4 -40°C to +85°C
DS4424N+T&R
4 -40°C to +85°C
+Denotes a lead-free package.
T&R = Tape and reel.
PIN-
PACKAGE
14 TDFN
14 TDFN
14 TDFN
14 TDFN
Features
Two (DS4422) or Four (DS4424) Current DACs
Full-Scale Current 50µA to 200µA
Full-Scale Range for Each DAC Determined by
External Resistors
127 Settings Each for Sink and Source Modes
I2C-Compatible Serial Interface
Two Address Pins Allow Four Devices on Same
I2C Bus
Low Cost
Small Package (14-Pin, 3mm x 3mm TDFN)
-40°C to +85°C Temperature Range
2.7V to 5.5V Operating Range
Pin Configuration appears at end of data sheet.
Typical Operating Circuit
RPU RPU
VCC
SDA
SCL
A1 DS4422/ OUT0
A0 DS4424 OUT1
GND
FS0
RFS0
FS1
RFS1
VCC VOUT0
OUT
DC-DC
CONVERTER
FB
R0A
R0B
VOUT1
OUT
DC-DC
CONVERTER
FB
R1A
R1B
_______________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.






DS4422 Datasheet, Funktion
Two-/Four-Channel, I2C, 7-Bit Sink/Source
Current DAC
Detailed Description
The DS4422/DS4424 contain two or four I2C adjustable
current sources that are each capable of sinking and
sourcing current. Each output (OUT0, OUT1, OUT2, and
OUT3) has 127 sink and 127 source settings that can be
controlled by the I2C interface. The full-scale ranges
and corresponding step sizes of the outputs are deter-
mined by external resistors, connected to pins FS0, FS1,
www.DataSheeFt4SU2.c,oamnd FS3, that can adjust the output current over a
4:1 range. Pins OUT2, OUT3, FS2, and FS3 are only
available on the DS4424.
The formula to determine RFS (connected to the FSx
pins) to attain the desired full-scale current range is:
Equation 1:
RFS
=
VRFS
16 × IFS
× 127
Where IFS is the desired full-scale current value, VRFS is
the RFS voltage (see the DC Electrical Characteristics
table), and RFS is the external resistor value.
To calculate the output current value (IOUT) based on the
corresponding DAC value (see Table 1 for corresponding
memory addresses), use equation 2.
Equation 2:
IOUT
=
DAC
Value(dec)
127
× IFS
On power-up the DS4422/DS4424 output zero current.
This is done to prevent them from sinking or sourcing an
incorrect amount of current before the system host con-
troller has had a chance to modify the device’s setting.
As a source for biasing instrumentation or other circuits,
the DS4422/DS4424 provide a simple and inexpensive
current source with an I2C interface for control. The
adjustable full-scale range allows the application to get
the most out of its 7-bit sink or source resolution.
When used in adjustable power-supply applications
(see Typical Operating Circuit), the DS4422/DS4424 do
not affect the initial power-up voltage of the supply
because they default to providing zero output current on
power-up. As the devices source or sink current into the
feedback-voltage node, they change the amount of out-
put voltage required by the regulator to reach its steady-
state operating point. Using the external resistor, RFS, to
set the output current range, the DS4422/DS4424 pro-
vide some flexibility for adjusting the impedances of the
feedback network or the range over which the power
supply can be controlled or margined.
I2C Slave Address
The DS4422/DS4424 respond to one of four I2C slave
addresses determined by the two address inputs, A0
and A1. The address inputs should be connected to
either VCC or ground. Table 1 lists the slave addresses
determined by the address input combinations.
Table 1. Slave Addresses
A1
GND
GND
VCC
VCC
A0
GND
VCC
GND
VCC
SLAVE ADDRESS
(HEX)
20h
60h
A0h
E0h
Memory Organization
To control the DS4422/DS4424’s current sources, write
to the memory addresses listed in Table 2.
Table 2. Memory Addresses
MEMORY ADDRESS
(HEX)
F8h
F9h
FAh*
FBh*
*Only for DS4424.
CURRENT SOURCE
OUT0
OUT1
OUT2*
OUT3*
The format of each output control register is given by:
MSB
LSB
S D6 D5 D4 D3 D2 D1 D0
Where:
BIT NAME
FUNCTION
POWER-ON
DEFAULT
S
Sign
Bit
Determines if DAC sources or
sinks current. For sink
S = 0; for source S = 1.
0b
7-Bit Data Controlling DAC
DX
Data
Output. Setting 0000000b
outputs zero current regardless
0000000b
of the state of the sign bit.
6 _______________________________________________________________________________________

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