L6710 STMicroelectronics, L6710 Datasheet - Page 20

• 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
The worst condition depends on the input voltage available and the output voltage selected. Anyway the
worst case is the response time after removal of the load with the minimum output voltage programmed
and the maximum input voltage available.
MAIN CONTROL LOOP
The control loop is composed by the Current Sharing control loop and the Average Current Mode control
loop. Each loop gives, with a proper gain, the correction to the PWM in order to minimize the error in its
regulation: the Current Sharing control loop equalize the currents in the inductors while the Average Cur-
rent Mode control loop fixes the output voltage equal to the reference programmed by VID. Figure 13 re-
ports the block diagram of the main control loop.
Figure 13. Main Control Loop Diagram
Current Sharing (CS) Control Loop
Active current sharing is implemented using the information from Tran conductance differential amplifier
in an average current mode control scheme.
A current reference equal to the average of the read current (I
read current and this reference is converted to a voltage with a proper gain and it is used to adjust the duty
cycle whose dominant value is set by the error amplifier at COMP pin (See fig. 14).
The current sharing control is a high bandwidth control loop allowing current sharing even during load tran-
sients.
The current sharing error is affected by the choice of external components; choose precise Rg resistor
(±1% is necessary) to sense the current.
The current sharing error is internally dominated by the voltage offset of Tran conductance differential am-
plifier; considering a voltage offset equal to 2mV across the sense resistor, the current reading error is
given by the following equation
20/34
D02IN1392
+
+
t
app lic atio n
4/5
COMP
AMPLIFIER
PWM1
PWM2
ERROR
1/5
1/5
=
∆ I
------------------- -
I
----------------------------- -
V
MAX
REA D
IN
Z
L ∆ I
F(S)
–
+
-
⋅
V
CORRECTION
DUTY CYCLE
=
OUT
CURRENT
SHARING
PROGRAMMED
REFERENCE
-------------------------------------- -
R
SENSE
BY VID
FB
2mV
R
⋅
t
re mov al
I
FB
MAX
I
I
AVG
INFO2
INFO1
L 1
L 2
) is internally built; the error between the
C
=
O
--------------
V
L ∆ I
OUT
⋅
R
O