L6710 STMicroelectronics, L6710 Datasheet - Page 11

• 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

Figure 2. Drivers peak current: High Side (left) and Low Side (right).
CURRENT READING AND OVER CURRENT
The current flowing trough each phase is read using the voltage drop across the low side mosfets R
or across a sense resistor (R
issued by the external resistor Rg placed outside the chip between ISENx and PGNDS pins toward the
reading points.
The differential current reading rejects noise and allows to place sensing element in different locations
without affecting the measurement's accuracy. The current reading circuitry reads the current during the
time in which the low-side mosfet is on (OFF Time). During this time, the reaction keeps the pin ISENx
and PGNDS at the same voltage while during the time in which the reading circuitry is off, an internal clamp
keeps these two pins at the same voltage sinking from the ISENx pin the necessary current (Needed if
low-side mosfet R
The proprietary current reading circuit allows a very precise and high bandwidth reading for both positive
and negative current. This circuit reproduces the current flowing through the sensing element using a high
speed Track & Hold transconductance amplifier. In particular, it reads the current during the second half
of the OFF time reducing noise injection into the device due to the mosfet turn-on (See fig. 3). Track time
must be at least 200ns to make proper reading of the delivered current.
This circuit sources a constant 100µA current from the PGNDS pin: it must be connected through two
equal Rg resistors to the groundside of the sensing element (See Figure 3). The two current reading cir-
cuitry uses this pin as a reference keeping the ISENx pin to this voltage.
The current that flows in the ISENx pin is then given by the following equation:
Where R
ductance resistor used between ISENx and PGNDS pins toward the reading points; I
carried by the relative phase. The current information reproduced internally is represented by the second
term of the previous equation as follow:
SENSE
CH3 = HGATE1; CH4 = HGATE2
is an external sense resistor or the R
dsON
sense is implemented to avoid absolute maximum rating overcome on ISENx pin).
SENSE
I
ISENx
) and internally converted into a current. The transconductance ratio is
=
50µA
I
INFO x
+
R
----------------------------------------------- -
SENSE
=
R
----------------------------------------------- -
SENSE
R
⋅
g
dsON
I
PHAS Ex
R
⋅
g
I
PHAS Ex
of the low side mosfet and Rg is the transcon-
=
CH3 = LGATE1; CH4 = LGATE2
50µA
+
I
INFO x
PHASEx
is the current
L6710
11/34
dsON