DS4426T+TR MAXIM [Maxim Integrated Products], DS4426T+TR Datasheet - Page 10

• Manufacturer Part Number: DS4426T+TR
• Description: Quad-Channel, I2C-Margining IDACs with Three Channels of Power-Supply Tracking
• Manufacturer: MAXIM [Maxim Integrated Products]

Quad-Channel, I
Three Channels of Power-Supply Tracking
Table 1. Slave Addresses
When enabling/disabling the power-supply tracking, a
resistor-divider connected to the THR input sets the dis-
able threshold (see V
of the resistor-divider must be connected to the master
DC-DC voltage for correct operation. Below this thresh-
old, the tracking circuit is active.
The DS4426 can be used to perform power-supply
sequencing. This is a subset of power-supply tracking
with modifications to the external resistor network. The
basic concept is that the DS4426 sources maximum
current into the slave power supply's feedback node
until a voltage in the system has risen above a specific
voltage level. By sourcing the maximum current into the
feedback node, the power supply's output is held off.
Maximum sourcing current is achieved with two steps:
1) Apply the maximum allowed input voltage across
2) Set the gain to the maximum allowed (R
The slave power supply is allowed to turn on once the
voltage on THR is greater than V
divider connected to the rising system voltage to scale
the trip point to V
The DS4426 responds to one of four I
es determined by the state of the input on the two
address inputs. The two input states are connected to
V
10
CC
INP and INN. Connect INP to V
voltage-divider to ground. Connect INN to ground.
or connected to ground.
______________________________________________________________________________________
GND
GND
V
V
A1
CC
CC
Inputs for Tracking in DC-DC Power
REF
GND
GND
V
V
A0
/2.
CC
CC
THRESHOLD
Power-Supply Sequencing
I
2
C Slave Address
SLAVE ADDRESS (HEX)
REF
in Figure 4). The top
CC
/2. Use a resistor-
2
2
C slave address-
Applications
90h
92h
94h
96h
- 1.4V using a
C-Margining IDACs with
L
/R
G
= 5).
Table 2. Memory Addresses
The DS4426’s current sources are controlled by writing
to memory addresses listed in Table 2.
The format of each of the output control registers is
given by:
where:
For example:
R
0xAAh. Use the following formula to calculate the out-
put current:
The MSB of the output register is 1, so the output is
sourcing the value corresponding to position 2Ah (42
decimal). The magnitude of the output current is equal
to the following:
(MSB)
BIT NAME
BIT 7
D
FS0
MEMORY ADDRESS (HEX)
S
X
S
= 80kΩ and register 0xF8h is written to a value of
Data
Sign
Bit
I
BIT 6
FS
D
6
99.22µA x (42/127) = 32.8125µA
= (1.0V/80kΩ) x (127/16) = 99.22µA
F8h
F9h
FAh
FBh
Determines if DAC sources or
sinks current. For sink, S = 0.
For source, S = 1.
7-bit data word controlling DAC
output. Setting 0000000b
outputs zero current regardless
of the state of the sign bit.
BIT 5
D
5
DESCRIPTION
Memory Organization
BIT 4
D
4
BIT 3
D
3
CURRENT SOURCE
BIT 2
D
2
OUT0
OUT1
OUT2
OUT3
BIT 1
POWER-ON
D
DEFAULT
0000000b
1
0b
(LSB)
BIT 0
D
0