L6714 STMicroelectronics, L6714 Datasheet - Page 54

• Manufacturer Part Number: L6714
• Description: IC CTRLR 4PH W/DRIVERS 64-TQFP
• Manufacturer: STMicroelectronics

Specifications of L6714

• Applications: Controller, Intel VR10, VR11, AMD CPU
• Voltage - Input: 12V
• Number Of Outputs: 4
• Voltage - Output: 0.3 ~ 1.6 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 64-TQFP Exposed Pad, 64-eTQFP, 64-HTQFP, 64-VQFP
• Mounting Style: SMD/SMT
• Case: QFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Oscillator
19
54/70
-------- -
6
Oscillator
L6714 embeds four phase oscillator with optimized phase-shift (90º phase-shift) in order to
reduce the input rms current and optimize the output filter definition.
The internal oscillator generates the triangular waveform for the PWM charging and
discharging with a constant current an internal capacitor. The switching frequency for each
channel, F
load side results in being multiplied by N (number of phases).
The current delivered to the oscillator is typically 25 A (corresponding to the free running
frequency F
between the OSC pin and SGND or VCC (or a fixed voltage greater than 1.24V). Since the
OSC pin is fixed at 1.24V, the frequency is varied proportionally to the current sunk (forced)
from (into) the pin considering the internal gain of 6KHz/ A.
In particular connecting R
pin), while connecting R
the pin), according the following relationships:
R
Hz
R
When using the Low-Side MOSFETs current sense, the maximum programmable switching
frequency per phase must be limited to 500kHz to avoid current reading errors causing, as a
consequence, current sharing errors.
Anyway, device power dissipation must be checked prior to design high switching frequency
systems.
A
kHz
---------- -
OSC
OSC
A
=
150 kHz
=
vs. SGND
vs. +12V
150 kHz 6.456
SW
SW
, is internally fixed at 150kHz so that the resulting switching frequency at the
F
+
F
= 150kHz) and it may be varied using an external resistor (R
SW
SW
–
7.422
-------------------------------
R
-------------------------------
R
OSC
=
=
OSC
150 kHz
150 kHz
k
10
OSC
k
10
OSC
3
4
to VCC = 12V the frequency is reduced (current is forced into
R
to SGND the frequency is increased (current is sunk from the
·
R
+
–
OSC
OSC
---------------------------
R
12V 1.240V
----------------------------------- -
1.240V
R
OSC
OSC
k
–
k
k
=
k
=
----------------------------------------------------------- -
F
----------------------------------------------------------- -
150 kHz
SW
6
kHz
---------- -
7.422
kHz
6
6.456
A
kHz
---------- -
=
A
–
150 kHz
–
=
150 kHz
F
10
150 kHz 6.456
SW
10
3
4
kHz
+
k
7.422
-------------------------------
R
–
k
-------------------------------
OSC
R
OSC
k
10
k
10
3
4
OSC
R
·
OSC
R
) connected
OSC
k
k
L6714
=
-----------
F
=
SW
-----
15