Analog Devices MAX77857, Руководство пользователя

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Evaluates: MAX77857 (WLP) MAX77857 Evaluation Kit
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J1 to position 1-2. This connects EN to V
IN
through a 510kΩ pullup resistor so that EN is controlled by V
IN
. Also, install
header jumper J2. This connects V
IO
to V
L
so that V
IO
is powered from V
L
, eliminating the need for an external V
IO
power
supply.
MAXUSB_INTERFACE#
The MAXUSB_INTERFACE# along with the companion EV kit GUI software allows users to easily change the
MAX77857’s register settings with a Windows PC. Before connecting the MAXUSB_INTERFACE# to the EV kit’s
MAXUSB_INTERFACE# connector (J5), make sure the MAXUSB_INTERFACE# is configured with the following settings:
•
SW1, SW2 to ON Position (This enables I
2
C mode on the MAXUSB_INTERFACE#.)
•
V
L
Jumper (J5) to 1.8V (This sets the MAXUSB_INTERFACE#’s V
IO
voltage.)
•
Warning: Setting this incorrectly to 3.3V could potentially damage the MAX77857 IC.
The MAXUSB_INTERFACE# also includes an on-board LDO that can supply the necessary voltage to V
IO
. If you are
using the MAXUS_INTERFACE#, disconnect any external V
IO
supply from the EV kit, and make sure header jumper J2
is removed from the EV kit.
External I
2
C Bus
If you wish to connect to the external I
2
C serial bus and not use the MAXUSB_INTERFACE#, unplug the
MAXUSB_INTERFACE# from the EV kit’s MAXUSB_INTERFACE# connector (J5). Apply an external I/O supply to the
V
IO
pin or power the V
IO
pin from the V
L
pin by connecting header jumper J2. Make sure the external I
2 C serial bus’s
logic voltag
e level is compatible with the MAX77857’s I/O logic voltage level. Refer to the
MAX77857 IC data sheet for
the appropriate I/O logic voltage level.
R
SEL
Configuration Resistor
The MAX77857 includes an SEL pin to set the I
2
C slave address, switching current limit, and feedback configuration. A
resistor with 1% tolerance (or better) should be chosen for R
SEL
(R9). The default R
SEL
value installed on the EV kit is
0Ω. See
Table 2 for nominal R
SEL
values and their corresponding settings. The switching current limit is also adjustable
dynamically through the I
2
C serial interface when the IC is enabled. See the EV Kit Software section for more information.
Table 2. MAX77857 R
SEL
Selection Table
R
SEL
(Ω)
FEEDBACK
RESISTOR
SELECTION
TYPICAL
I
LIM
(A)
I
2
C SLAVE
ADDRESS
(7-BIT)
R
SEL
(Ω)
FEEDBACK
RESISTOR
SELECTION
TYPICAL
I
LIM
(A)
I
2
C SLAVE
ADDRESS
(7-BIT)
0*
Internal
feedback
resistors
7.0
110 0110 (0x66) 3740
External
feedback
resistors
7.0
110 0110 (0x66)
200 110 0111 (0x67) 8060 110 0111 (0x67)
309 110 1110 (0x6E) 12400 110 1110 (0x6E)
(0x6E) (0x6E)
422 110 1111 (0x6F) 16900 110 1111 (0x6F)
536
5.6
110 0110 (0x66) 21500
5.6
110 0110 (0x66)
649 110 0111 (0x67) 26100 110 0111 (0x67)
768 110 1110 (0x6E) 30900 110 1110 (0x6E)
909 110 1111 (0x6F) 36500 110 1111 (0x6F)
1050
3.8
110 0110 (0x66) 42200
3.8
110 0110 (0x66)
1210 110 0111 (0x67) 48700 110 0111 (0x67)
1400 110 1110 (0x6E) 56200 110 1110 (0x6E)
1620 110 1111 (0x6F) 64900 110 1111 (0x6F)
1870
1.8
110 0110 (0x66) 75000
1.8
110 0110 (0x66)
2150 110 0111 (0x67) 86600 110 0111 (0x67)
2490 110 1110 (0x6E) 100000 110 1110 (0x6E)
2870 110 1111 (0x6F) OPEN 110 1111 (0x6F)
*Default value installed on the EV Kit