ltc3528b-2 Linear Technology Corporation, ltc3528b-2 Datasheet - Page 9

• Manufacturer Part Number: ltc3528b-2
• Description: 1a, 2mhz Synchronous Step-up Dc/dc Converter In 2mm ? 3mm Dfn
• Manufacturer: Linear Technology Corporation

Current Sensing
Lossless current sensing converts the peak current signal
of the N-channel MOSFET switch into a voltage which
is summed with the internal slope compensation. The
summed signal is compared to the error amplifi er output to
provide a peak current control command for the PWM.
Current Limit
The current limit comparator shuts off the N-channel
MOSFET switch once its threshold is reached. The current
limit comparator delay to output is typically 60ns. Peak
switch current is limited to approximately 1.5A, indepen-
dent of input or output voltage, unless V
0.7V, in which case the current limit is cut in half.
Zero Current Comparator
The zero current comparator monitors the inductor cur-
rent to the output and shuts off the synchronous rectifi er
when this current reduces to approximately 20mA. This
prevents the inductor current from reversing in polarity,
improving effi ciency at light loads.
Synchronous Rectifi er
To control inrush current and to prevent the inductor
current from running away when V
P-channel MOSFET synchronous rectifi er is only enabled
when V
OPERATION
OUT
> (V
IN
+ 0.24V).
(Refer to Block Diagram)
OUT
is close to V
OUT
falls below
IN
, the
Anti-Ringing Control
The anti-ringing control connects a resistor across the
inductor to prevent high frequency ringing on the SW pin
during discontinuous current mode operation. The ringing
of the resonant circuit formed by L and C
on SW pin) is low energy, but can cause EMI radiation.
Output Disconnect
The LTC3528B-2 is designed to allow true output discon-
nect by eliminating body diode conduction of the internal
P-channel MOSFET rectifi er. This allows for V
zero volts during shutdown, drawing no current from the
input source. It also enables inrush current limiting at turn-
on, minimizing surge currents seen by the input supply.
Note that to obtain the advantages of output disconnect,
a Schottky diode cannot be connected between SW and
V
forced above the programmed regulation voltage, without
any reverse current into a battery on V
Thermal Shutdown
If the die temperature exceeds 160°C, the LTC3528B-2
enters thermal shutdown. All switches will be turned off
and the soft-start capacitor will be discharged. The device
will be enabled again when the die temperature drops by
approximately 15°C.
OUT
. The output disconnect feature also allows V
LTC3528B-2
IN
.
SW
(capacitance
OUT
OUT
to go to
to be
3528b2f
9