L6910 STMicroelectronics, L6910 Datasheet - Page 5

• Manufacturer Part Number: L6910
• Description: IC PWM BUCK BST VM 16SOIC
• Manufacturer: STMicroelectronics

Specifications of L6910

• Pwm Type: Voltage Mode
• Number Of Outputs: 1
• Frequency - Max: 230kHz
• Duty Cycle: 100%
• Voltage - Supply: 5 V ~ 12 V
• Buck: Yes
• Boost: Yes
• Flyback: No
• Inverting: No
• Doubler: No
• Divider: No
• Cuk: No
• Isolated: No
• Operating Temperature: -40°C ~ 150°C
• Package / Case: 16-SOIC (3.9mm Width)
• Frequency-max: 230kHz
• Output Voltage: 4 V
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: 497-3656-5; 497-4220-5; 497-4220-5

4
The device is an integrated circuit realized in BCD technology. The controller provides complete con-
trol logic and protection for a high performance step-down DC-DC converter. It is designed to drive N
Channel Mosfets in a synchronous-rectified buck topology. The output voltage of the converter can be
precisely regulated down to 900mV with a maximum tolerance of ±1.5% when the internal reference is
used (simply connecting together EAREF and VREF pins). The device allows also using an external
reference (0.9V to 3V) for the regulation. The device provides voltage-mode control with fast transient
response. It includes a 200kHz free-running oscillator that is adjustable from 50kHz to 1MHz. The er-
ror amplifier features a 10MHz gain-bandwidth product and 10V/ s slew rate that permits to realize
high converter bandwidth for fast transient performance. The PWM duty cycle can range from 0% to
100%. The device protects against over-current conditions entering in HICCUP mode. The device
monitors the current by using the r
rent sensing resistor. The device is available in SO16 narrow package.
4.1 Oscillator
The switching frequency is internally fixed to 200kHz. The internal oscillator generates the triangular waveform
for the PWM charging and discharging with a constant current an internal capacitor. The current delivered to the
oscillator is typically 50 A (F
OSC pin and GND or V
ied proportionally to the current sunk (forced) from (into) the pin.
In particular connecting R
following relationship:
Connecting R
to the following relationships:
Switching frequency variation vs. RT are repeated in Fig. 4.
Note that forcing a 50 A current into this pin, the device stops switching because no current is delivered to the
oscillator.
Figure 4.
DEVICE DESCRIPTION
T
to V
CC
= 12V or to V
CC
. Since the OSC pin is maintained at fixed voltage (typ. 1.235V), the frequency is var-
T
vs. GND the frequency is increased (current is sunk from the pin), according to the
sw
f
OSC,RT
= 200KHz) and may be varied using an external resistor (R
f
OSC,RT
10000
CC
1000
100
DS(ON)
f
10
OSC,RT
=
= 5V the frequency is reduced (current is forced into the pin), according
10
=
200KHz
200KHz
of the upper MOSFET(s) that eliminates the need for a cur-
=
200KHz
–
Frequency [kHz]
RT to GND
RT to VCC=12V
RT to VCC=5V
4.306 10
---------------------------- -
–
R
---------------------
R
15 10
T
T
100
K
K
+
4.94 10
-------------------------
R
6
7
T
K
V
V
6
CC
CC
= 5V
1000
= 12V
T
) connected between
L6910 - L6910A
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