RT6210
Functional Block Diagram
VIN
EN
HV
Protection
-
1.2V
1µA
Thermal
Shutdown
UVLO
Internal
Regulator
+
Shutdown
Comparator
Current
Sense
BOOT
UVLO
BOOT
HS
SW
LS
HS Switch
Current
Comparator
0.4V
+
-
UV
Comparator
-
+ EA
+
Logic &
Clamp
Control
Gate Driver
with Dead
Time Control
FB
0.8V
6µA
LS Switch
Current
Comparator
Oscillator
Current
Sense
SS
COMP
Slope
Compensation
GND
Operation
The RT6210 is a synchronous step-down converter,
integrated with both high-side (HS) and low-side (LS)
MOSFETs to reduce external component count and a gate
driver with dead-time control logic to prevent shoot-through
condition from happening. The RT6210 also features
constant frequency and peak current-mode control with
slope compensation. During PWM operation, output
voltage is regulated down, and is sensed from the FB pin
to be compared with an internal 0.8V reference voltage
V
REF
. In normal operation, the high-side N-MOSFET is
turned on when an S-R latch is set by the rising edge of
an internal oscillator output as the PWM clock, and is
turned off when the S-R latch is reset by the output of a
(high-side) current comparator, which compares the high-
side sensed current signal with the current signal related
to the COMP voltage. While the high-side N-MOSFET is
turned off, the low-side N-MOSFET will be turned on. If
the output voltage is not established, the high-side power
switch will be turned on again and another cycle begins.
Pulse Skipping Operation
At very light-load condition, the RT6210 provides pulse
skipping technique to decrease switching loss for better
efficiency. When load current decreases, the FB voltage
V
FB
will increase slightly. With V
FB
1% higher than V
REF
,
the COMP voltage will be clamped at a minimum value
and the converter will enter into pulse skipping mode. When
the converter operates in pulse skipping mode, the internal
oscillator will be stopped, which makes the switching period
being extended. In pulse skipping mode, as the load
current decreases, V
FB
will be discharged more slowly,
which in turn will extend the switching period even more.
Error Amplifier
The RT6210 adopts a transconductance amplifier as the
error amplifier. The error amplifier of a typical 970μA/V
transconductance (gm) compares the feedback voltage
V
FB
with the lower one of the soft-start voltage or the
internal reference voltage V
REF
, 0.8V. As V
FB
drops due
to the load current increase, the output voltage of the error
Copyright
©
2019 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS6210-01 February 2019
www.richtek.com
3
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