Datasheet

MAX8660/MAX8660A/MAX8660B/MAX8661
High-Efficiency, Low-I
Q
, PMICs with Dynamic
Voltage Management for Mobile Applications
38
1
S
NUMBER OF BITS
R/W
SLAVE ADDRESS
7
0
18
REGISTER POINTER
1 18
DATA A
1
P
1
SLAVE TO MASTER
MASTER TO SLAVE
LEGEND
1
S
R/W
SLAVE ADDRESS
7
0
18
REGISTER POINTER XA
1
A
A
18
DATA X A
1
P
1
8
REGISTER POINTER n A
18
DATA n A
1
8
REGISTER POINTER Z A
18
DATA Z A
1
A. WRITING TO A SINGLE REGISTER WITH THE “WRITE BYTE” PROTOCOL
B. WRITING TO MULTIPLE REGISTERS WITH THE “MULTIPLE-BYTE REGISTER-DATA PAIR” PROTOCOL
NUMBER OF BITS
NUMBER OF BITS
NUMBER OF BITS
A A
Figure 11. Writing to the MAX8660/MAX8661
Design Procedure
Setting the Output Voltages
The REG1 and REG2 regulators each have three preset
voltages that are programmed with the SET1 and SET2
inputs. See the REG1 (VCC_IO) Step-Down DC-DC
Converter (MAX8660 Only) and REG2 (VCC_IO,
VCC_MEM) Step-Down DC-DC Converters sections for
more information. V8 is fixed at 3.3V and cannot be
changed.
V3–V7 are set by the I
2
C interface. See the I
2
C
Interface section for more information. Note that while
operating in forced-PWM mode with an input voltage
greater than 4.3V, the minimum output voltage of REG3
and REG4 is limited by the minimum duty cycle. In
forced-PWM mode, the minimum output voltage for
REG3 or REG4 is:
Note that the above minimum voltage limitation does
not apply to normal-mode operation.
Inductor Selection
Calculate the inductor value (L
IDEAL
) for each of REG1
through REG4 as follows:
This sets the peak-to-peak inductor current ripple to 1/4
the maximum output current. The oscillator frequency,
f
OSC
, is 2MHz, and the duty cycle, D, is:
Given L
IDEAL
, the peak-to-peak inductor ripple current
is 0.25 x I
OUT(MAX)
. The peak inductor current is 1.125
x IOUT(MAX). Make sure that the saturation current of the
inductor exceeds the peak inductor current, and the
rated maximum DC inductor current exceeds the maxi-
mum output current (I
OUT(MAX)
). Inductance values
smaller than L
IDEAL
can be used to reduce inductor
size; however, if much smaller values are used, peak
inductor current rises and a larger output capacitance
may be required to suppress output ripple. Larger
D
V
V
OUT
IN
=
L
xV xDx D
Ixf
IDEAL
IN
OUT MAX OSC
=
−41()
()
VxV
VxV
MIN PV
MIN PV
3 0 167
4 0 167
3
4
=
=
.
.