XR77103 Datasheet, PDF (24/28 Pages) Exar Corporation – 3-Output Programmable Buck Regulator

XR77103
Applications Information (Continued)
Switching Frequency and Phase Register (09h)
Switching frequency and phase register has 7 effective bits.
The 5 least significant bits are setting switching frequency.
The factory default value is 500kHz (00010b).
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
X
D6
D5
D4
D3
D2
D1
D0
D [4:0] Hex
00
01
02
03
04
05
06
07
08
09
f_SW [MHz]
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
D [4:0] Hex
0A
0B
0C
0D
0E
0F
10
11
12
13
f_SW [MHz]
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2
2.1
2.2
PWR Register (0Ah)
PWR register has 5 effective bits. The bits 0-2 select which
channels will be enabled at transition of ENABLE pin from
low to high. The state of the bit 3 determines whether
buck converters operate in Pulse Skipping Mode or not.
Setting this bit to 1 allows Pulse Skipping Mode operation
to minimize power losses at light load levels. The bit 6
determines threshold voltage for V_IN UVLO. The factory
default of this register is 7Fh.
Bit 7
X
Bit 6
UV
Bit 5
X
Bit 4
X
Bit 3 Bit 2 Bit 1 Bit 0
PSM
BUCK BUCK BUCK
3
2
1
0
1
D0
BUCK 1
Not Used
Select
D1
BUCK 2
Not Used
Select
D2
BUCK 3
Not Used
Select
D3
PSM
Disable
Enable
D6
UV
4.2V
7V
The bits 5 and 6 are for setting phase shift among buck
converters. The factory default value is channel 3 180°
out-of-phase in respect to the channels 1 and 2 (10b).
D6
D5
Phase Shift
0
0
All converters operate in phase
0
1
1
0
1
1
Buck1 and Buck2/3 operate
180° out-of-phase
Buck1/2 and Buck3 operate
180° out-of-phase
Buck1/3 and Buck2 operate
180° out-of-phase
REV1B
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