XRP7714ILB-0X10-F Exar Corporation, XRP7714ILB-0X10-F Datasheet - Page 20

• Manufacturer Part Number: XRP7714ILB-0X10-F
• Description: IC CTRLR PWM/LDO STP-DWN 40TQFN
• Manufacturer: Exar Corporation
• Series: -r

Specifications of XRP7714ILB-0X10-F

• Topology: Step-Down (Buck) Synchronous (4), Linear (LDO) (1)
• Function: Any Function
• Number Of Outputs: 5
• Frequency - Switching: 1.5MHz
• Voltage/current - Output 1: Controller
• Voltage/current - Output 2: Controller
• Voltage/current - Output 3: Controller
• W/led Driver: No
• W/supervisor: No
• W/sequencer: Yes
• Voltage - Supply: 4.75 V ~ 25 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: *
• Package / Case: *
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 1016-1701

There are a number of options that could result in similar PWM switching frequency as shown
above. In general, the chip consumes less power at lower oscillator frequency. When
synchronization of the Main Oscillator Frequency to an external system clock is desired, the user
must choose the oscillator frequency to be within ±5% of the external clock frequency. A higher
Main Oscillator frequency will not improve accuracy or any performance efficiency.
Note: It is the intention of the synchronization feature to sync to a system clock or to another
compatible Exar device, not the switching frequency.
PWM S
There are several considerations when choosing the PWM switching frequency.
Minimum on time determines the minimum duty cycle at the specific switching frequency. The
minimum on time for the XRP7714 is 40ns.
As an example the minimum duty cycle is 4% for 1MHz PWM frequency. This is important since the
minimum on time dictates the maximum conversion ratio that the PWM controller can achieve.
The maximum duty cycle is dictated by the minimum required time to sample the current when the
low side MOSFET is on, this depends on the frequency of the main oscillator and the selected PWM
frequency. It is best to choose the highest main oscillator frequency available for any specific PWM
frequency. The maximum duty cycle for each PWM frequency is shown in the table below:
© 2011 Exar Corporation
PWM Switching Frequency
Minimum On Time
Maximum Duty Cycle
SET_SW_FREQUENCY[2:0]
Maximum Duty Cycle
WITCHING
78%
86%
84%
89%
88%
88%
86%
000
001
010
011
100
101
110
111
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F
REQUENCY
600KHZ
429KHZ
600KHZ
429KHZ
750KHz
500KHz
375KHz
750KHz
500KHz
375KHz
1.5MHz
1.0MHz
1.5MHz
1.0MHz
C
48MHz
000
ONSIDERATIONS
NA
Q
Q
�������������� �������� ����������% >
u
u
a
a
d
d
Fig. 26: PWM Frequency
44.8MHz 41.6MHz 38.4MHz 35.2MHz
467KHZ
400KHZ
467KHZ
400KHZ
933KHz
700KHz
560KHz
350KHz
933KHz
700KHz
560KHz
350KHz
1.4MHz
1.4MHz
001
C
C
NA
h
h
a
a
20/29
n
n
n
n
867KHz
650KHz
520KHz
433KHz
370KHz
325KHz
867KHz
650KHz
520KHz
433KHz
370KHz
325KHz
1.3MHz
1.3MHz
e
e
010
NA
l
l
SET_SW_FREQUENCY[6:4]
Main Oscillator Frequency
D
D
i
i
g
g
������������
800KHz
600KHz
480KHz
400KHz
343KHz
300KHz
800KHz
600KHz
480KHz
400KHz
343KHz
300KHz
1.2MHz
1.2MHz
i
i
��������
t
t
011
NA
a
a
l
l
P
P
W
W
733KHz
550KHz
440KHz
367KHz
314KHz
733KHz
550KHz
440KHz
367KHz
314KHz
1.1MHz
1.1MHz
M
100
M
NA
NA
NA
S
S
t
t
e
e
667KHz
500KHz
400KHz
333KHz
667KHz
500KHz
400KHz
333KHz
1.0MHz
1.0MHz
p
p
32MHz
101
NA
NA
NA
NA
NA
D
D
o
o
w
w
28.8Mhz
900KHz
600KHz
450KHz
360KHz
300KHz
900KHz
600KHz
450KHz
360KHz
300KHz
n
n
110
X
X
NA
NA
NA
NA
NA
C
C
R
R
o
o
n
P
n
P
Rev. 1.1.6
t
t
7
7
25.6MHz
800KHz
533KHz
400KHz
320KHz
800KHz
533KHz
400KHz
320KHz
r
r
o
o
111
7
7
NA
NA
NA
NA
NA
NA
NA
l
l
1
1
l
l
e
e
4
4
r
r