LTC3850EUF#PBF Linear Technology, LTC3850EUF#PBF Datasheet - Page 9

• Manufacturer Part Number: LTC3850EUF#PBF
• Description: IC CNTRLR STP DWN SYNC 28-QFN
• Manufacturer: Linear Technology
• Series: PolyPhase®r
• Type: Step-Down (Buck)r

Specifications of LTC3850EUF#PBF

• Internal Switch(s): No
• Synchronous Rectifier: Yes
• Number Of Outputs: 2
• Voltage - Output: 0.8 ~ 23.3 V
• Current - Output: 100mA
• Frequency - Switching: 250kHz ~ 780kHz
• Voltage - Input: 4 ~ 24 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 28-QFN
• Primary Input Voltage: 24V
• No. Of Outputs: 2
• Output Current: 100mA
• No. Of Pins: 28
• Operating Temperature Range: -40°C To +85°C
• Msl: MSL 1 - Unlimited
• Supply Voltage Range: 4V To 24V
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -

PIN FUNCTIONS
RUN1, RUN2 (Pins 1, 13/Pins 26, 9/Pins 27, 10): Run
Control Inputs. A voltage above 1.2V on either pin turns
on the IC. However, forcing either of these pins below 1.2V
causes the IC to shut down that particular channel. There
are 0.5µA pull-up currents for these pins. Once the RUN
pin rises above 1.2V, an additional 4.5µA pull-up current
is added to the pin.
SENSE1
Current Sense Comparator Inputs. The (+) inputs to the
current comparators are normally connected to DCR sens-
ing networks or current sensing resistors.
SENSE1
Current Sense Comparator Inputs. The (–) inputs to the
current comparators are connected to the outputs.
TK/SS1, TK/SS2 (Pins 4, 10/Pins 1, 6/Pins 2, 7): Output
Voltage Tracking and Soft-Start Inputs. When one channel
is configured to be master of the two channels, a capaci-
tor to ground at this pin sets the ramp rate for the master
channel’s output voltage. When the channel is configured
to be the slave of two channels, the V
master channel is reproduced by a resistor divider and
applied to this pin. Internal soft-start currents of 1.3µA
charge the soft-start capacitors.
I
Thresholds and Error Amplifier Compensation Points.
Each associated channels’ current comparator tripping
threshold increases with its I
V
Feedback Inputs. These pins receive the remotely sensed
feedback voltages for each channel from external resistive
dividers across the outputs.
SGND (Pin 7/Pin 29/Pin 29): Signal Ground. All small-
signal components and compensation components should
connect to this ground, which in turn connects to PGND
at one point. Pin 29 is the Exposed Pad, only available on
the UF package.
EXTV
Power Input to an Internal Switch Connected to INTV
This switch closes and supplies the IC power, bypassing
the internal low dropout regulator, whenever EXTV
higher than 4.7V. Do not exceed 6V on this pin and ensure
TH1
FB1
, I
, V
CC
TH2
FB2
(Pin 14, LTC3850-1 Only/Pin 11/Pin 12): External
+
–
, SENSE2
, SENSE2
(Pins 5, 9/Pins 2, 5/Pins 3, 6): Current Control
(Pins 6, 8/Pins 3, 4/Pins 4, 5): Error Amplifier
+
–
(Pins 2, 12/Pins 27, 8/Pins 28, 9):
(Pins 3, 11/Pins 28, 7/Pins 1, 8):
(GN/UF/UFD)
TH
control voltage.
FB
voltage of the
CC
CC
is
.
V
is the optional bonding in place of I
the LTC3850-1, I
I
Comparator Sense Voltage Range Inputs. Tying this pin to
SGND, FLOAT or INTV
threshold to three different levels for each comparator.
PGOOD (Pin 15/Pin 12/Pin 13): Power Good Indicator
Output. Open-drain logic out that is pulled to ground when
either channel output exceeds the ±7.5% regulation window,
after the internal 17µs power bad mask timer expires.
PGND (Pin 19/Pin 16/Pin 17): Power Ground Pin. Connect
this pin closely to the sources of the bottom N-channel
MOSFETs, the (–) terminal of CV
of C
INTV
The control circuits are powered from this voltage.
Decouple this pin to PGND with a 4.7µF low ESR tantalum
or ceramic capacitor.
V
this pin to PGND with a capacitor (0.1µF to 1µF). For ap-
plications where the main input power is 5V, tie the V
and INTV
BG1, BG2 (Pins 23, 20/Pins 20, 17/Pins 21, 18): Bottom
Gate Driver Outputs. These pins drive the gates of the
bottom N-Channel MOSFETs and swings between PGND
and INTV
BOOST1, BOOST2 (Pins 24, 18/Pins 21, 15/Pins 22, 16):
Boosted Floating Driver Supplies. The (+) terminal of the
boost-strap capacitors connect to these pins. These pins
swing from a diode voltage drop below INTV
+ INTV
TG1, TG2 (Pins 25, 17/Pins 22, 14/Pins 23, 15): Top Gate
Driver Outputs. These are the outputs of floating drivers
with a voltage swing equal to INTV
the switch nodes voltages.
SW1, SW2 (Pins 26, 16/Pins 23, 13/Pins 24, 14): Switch
Node Connections to Inductors. Voltage swing at these
pins are from a body diode voltage drop below ground
to V
LIM
IN
IN
(Pin 22/Pin 19/Pin 20): Main Input Supply. Decouple
> V
IN
IN
CC
(Pin 14, LTC3850 Only/Pin 10/Pin 11): Current
.
.
CC
(Pin 21/Pin 18/Pin 19): Internal 5V Regulator Output.
EXTVCC
.
CC
CC
.
pins together.
at all times. On the GN package, EXTV
LTC3850/LTC3850-1
LIM
will default to 50mV.
CC
sets the maximum current sense
CC
LIM
CC
and the (–) terminal
superimposed on
for LTC3850-1. In
CC
up to V
38501fc
9
CC
IN
IN