L6710 STMicroelectronics, L6710 Datasheet - Page 13

• Manufacturer Part Number: L6710
• Description: IC CTRLR 6BIT 2PH PROGR 44-TQFP
• Manufacturer: STMicroelectronics
• Type: Step-Down (Buck)r

Specifications of L6710

• Internal Switch(s): No
• Synchronous Rectifier: Yes
• Number Of Outputs: 2
• Voltage - Output: 0.84 ~ 1.6 V
• Current - Output: 2A
• Frequency - Switching: 150kHz
• Voltage - Input: 12V
• Operating Temperature: 0°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 44-TQFP, 44-VQFP
• Power - Output: 2.5W
• Product: Half-Bridge Drivers
• Supply Current: 12.5 mA
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

1.
This happens when the maximum ON time is reached before the current in each phase reaches I
(I
Figure 4a shows the maximum output voltage that the device is able to regulate considering the T
itation imposed by the previous relationship. If the desired output characteristic crosses the T
maximum output voltage, the output resulting voltage will start to drop after crossing. In this case, the de-
vice doesn't perform constant current limitation but only limits the maximum ON time following the previous
relationship. The output voltage follows the resulting characteristic (dotted in Figure 4b) until UVP is de-
tected or anyway until I
Figure 4. T
2.
This happens when ON time limitation is reached after the current in each phase reaches I
>35µA).
The device enters in Quasi-Constant-Current operation: the low-side mosfets stays ON until the current
read becomes lower than I
ON with a T
usual way until another OCP event is detected.
This means that the average current delivered can slightly increase also in Over Current condition since
the current ripple increases. In fact, the ON time increases due to the OFF time rise because of the current
has to reach the I
When this happens, the device works in Constant Current and the output voltage decrease as the load
increase. Crossing the UVP threshold causes the device to latch (FAULT pin is driven high).
Figure 5 shows this working condition.
It can be observed that the peak current (Ipeak) is greater than the IOCPx but it can be determined as
follow:
Where V
The device works in Constant-Current, and the output voltage decreases as the load increase, until the
INFOx
T
CONSTANT CURRENT OPERATION
0.80·V
0.40·V
ON
<35 A).
V
OUT
outMIN
LIMITED OUTPUT VOLTAGE.
IN
IN
ON
a) Maximum output Voltage
ON
Limited Operation
is the minimum output voltage (VID-40% as follow).
imposed by the control loop at the next available clock cycle and the device works in the
OCPx
I
pea k
bottom. The worst-case condition is when the ON time reaches its maximum value.
FB
T
=
ON
= 70 µA
OCPx
I
Limited Output
OCPx
characteristic
I
OCP
(I
(I
FB
+
INFOx
=2·I
=70 µ A)
V
------------------------------------ - Ton
IN
OCPx
–
< 35µA) skipping clock cycles. The high side mosfets can be turned
Vout
L
I
OUT
mi n
⋅
M AX
=
0.80·V
0.40·V
I
OCPx
V
OUT
IN
IN
+
V
------------------------------------- - 0.40 T
I N
b) T
–
Vout
L
ON
Limited Output Voltage
M IN
⋅
I
(I
OCP
⋅
FB
characteristic and
=2·I
=70 µ A)
Resulting Output
Desired Output
UVP threshold
OCPx
characteristic
OCPx
ON
I
OUT
L6710
ON
limited
(I
INFOx
13/34
OCPx
lim-