L6710 STMicroelectronics, L6710 Datasheet - Page 14

• 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

L6710
output voltage reaches the under-voltage threshold (V
are turned off, the FAULT pin is driven high and the device stops working. Cycle the power supply to re-
start operation.
The maximum average current during the Constant-Current behavior results:
In this particular situation, the switching frequency results reduced. The ON time is the maximum allowed
(TonMAX) while the OFF time depends on the application:
Over current is set anyway when I
The full load value is only a convention to work with convenient values for I
threshold is fixed, to modify the percentage with respect to the load value, it can be simply considered that,
for example, to have on OCP threshold of 200%, this will correspond to I
full load current will then correspond to I
Figure 5. Constant Current operation
INTEGRATED DROOP FUNCTION
The device uses a droop function to satisfy the requirements of high performance microprocessors, re-
ducing the size and the cost of the output capacitor.
This method "recovers" part of the drop due to the output capacitor ESR in the load transient, introducing
a dependence of the output voltage on the load current: the regulated voltage decrease as the load in-
crease with a precise relationship.
As shown in figure 6, the ESR drop is present in any case, but using the droop function the total deviation
of the output voltage is minimized. A static error (V
a resistor between FB and GND allowing to exploit the all tolerance interval available. This additional re-
sistor is not required in application such as VRD10 since the nominal value is already set by the VID* and
the load regulation fixed by the specs.
Since the device has an average current mode regulation, the information about the total current delivered
14/34
TonMAX
a) Maximum current for each phase
T
O FF
I
TonMAX
MA X,TOT
=
L
INFOx
⋅
Ipeak I
------------------------------------- -
=
reaches 35µA (I
INFOx
V
2 I
OU t
⋅
–
MA X
OCPx
= 17.5µA (I
=
2
DROOP
⋅


I
outMIN
OCPx
FB
Ipeak
I
I
FB
MAX
OCPx
in figure 6) at zero load is simply introduced by
=70µA).
+
). When this threshold is crossed, all mosfets
= 35µA).
Ipeak I
------------------------------------- -
f
=
-----------------------------------------
T
ONm ax
2
–
UVP
Vout
OCPx
b) Output Characteristic
1
(I
+
FB
INFOx
=50µA)


T
FB
O FF
. Since the OCP intervention
= 35µA (I
Droop effect
2·I
OCPx
(I
FB
=70µA)
FB
I
MAX,TOT
= 70µA). The
Iout