®
RTQ2132B-QT
1.2A, 36V, 2.1MHz Synchronous Step-Down Converter
General Description
The RTQ2132B is a 1.2A, high-efficiency, current mode
synchronous step-down converter which is optimized for
automotive applications. The device operates with input
voltages from 3V to 36V and is protected from load dump
transients up to 42V, eases input surge protection design.
The device can program the output voltage between 0.8V
to V
IN
. The integrated low R
DS(ON)
power MOSFETs
achieves high efficiency over the wide load range. The peak
current mode control with simple external compensation
allows the use of small inductors and results in fast
transient response and good loop stability.
The RTQ2132B provides complete protection functions
such as input under-voltage lockout, output-under voltage
protection, over-current protection, and thermal shutdown.
Cycle-by-cycle current limit provides protection against
shorted outputs and soft-start eliminates input current
surge during start-up. The RTQ2132B is available in
TSSOP-14 (Exposed Pad) package.
Features
AEC-Q100 Grade 1 Qualified
Wide Input Voltage Range
½
3V to 36V
Tight Switching Frequency Variation 2.1MHz
±
10%
Over Operating Ambient Temperature
Wide Output Voltage Range : 0.8V to V
IN
5V Fixed Output Voltage (see Ordering Information
for availability)
Maximum Output Current : 1.2A
Peak Current Mode Control
Ω
Ω
Integrated 200mΩ Switch and 160mΩ Synchronous
Rectifier
Built-In Spread-Spectrum Frequency Modulation for
Low EMI
Externally Adjustable Soft-Start
Power Good Indication
Enable Control
0.8V
±
1.5% CV Reference Accuracy
Adjacent Pin-Short Protection
Built-In UVLO, UVP, OTP
Ordering Information
RTQ2132B (-
)
-QT
Grade
QT : AEC-Q100 Qualified
Package Type
CP : TSSOP-14 (Exposed Pad-Option 2)
Lead Plating System
G : Green (Halogen Free and Pb Free)
Fixed Output Voltage
50 : 5V
Applications
Automotive Systems
Car Camera Module and Car Cockpit Systems
Connected Car Systems
Point of Load Regulator in Distributed Power Systems
Digital Set Top Boxes
Broadband Communications
Note :
Richtek products are :
½
Pin Configuration
(TOP VIEW)
VIN
NC
BOOT
SW
NC
PGND
SS
14
2
3
4
5
6
7
15
13
12
RoHS compliant and compatible with the current require-
ments of IPC/JEDEC J-STD-020.
Suitable for use in SnPb or Pb-free soldering processes.
½
PAD
11
10
9
8
VCC
PGOOD
EN
NC
FB/VS
COMP
AGND
TSSOP-14 (Exposed Pad)
Copyright
©
2018 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DSQ2132B-QT-01 August 2018
www.richtek.com
1
RTQ2132B-QT
Marking Information
RTQ2132BGCP-QT
RTQ2132BGCP-QT : Product Number
RTQ2132B-50GCP-QT
RTQ2132B50GCP-QT : Product Number
YMDNN : Date Code
RTQ2132B
GCP-QTYMDNN
RTQ2132B50
GCP-QTYMDNN
YMDNN : Date Code
Functional Pin Description
Pin No.
1
2, 5, 11
3
4
6
7
8
9
Pin Name
VIN
NC
BOOT
SW
PGND
SS
AGND
COMP
Pin Function
Power input. The input voltage range is from 3V to 36V after soft-start is
finished. Connect input capacitors between this pin and PGND. It is
recommended to use a 2.2F, X7R and a 0.1F, X7R capacitors.
No internal connection.
Bootstrap capacitor connection node to supply the high-side gate driver.
Connect a 0.1F, X7R ceramic capacitor between this pin and SW pin.
Switch node. SW is the switching node that supplies power to the output and
connect the output LC filter from SW to the output load.
Power ground.
Soft-start capacitor connection node. Connect an external capacitor between
this pin and ground to set the soft-start time.
Analog ground.
Compensation node. Connect external compensation elements to this pin to
stabilize the control loop.
Output voltage sense. There are two output voltage setting options : one is
that trimmed output voltage options for a fixed output voltage are available for
the VS pin, and the other is through a resistive divider to sense the output
voltage at the FB pin. The feedback reference voltage is 0.8V typically.
Enable control input. A logic-high enables the converter; a logic-low forces
the device into shutdown mode.
Open-drain power-good indication output. Once soft-start is finished,
PGOOD will be pulled low to ground if any internal protection is triggered.
Linear regulator output. VCC is the output of the internal 5V linear regulator
powered by VIN. Decouple with a 1F, X7R ceramic capacitor from VCC to
ground for normal operation.
Exposed pad. The exposed pad is internally unconnected and must be
soldered to a large PGND plane. Connect this PGND plane to other layers
with thermal vias to help dissipate heat from the device.
10
FB/VS
12
13
14
EN
PGOOD
VCC
15 (Exposed Pad)
PAD
Copyright
©
2018 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
2
DSQ2132B-QT-01 August 2018
RTQ2132B-QT
Functional Block Diagram
Adjustable Output Voltage
PGOOD
VIN
VCC
EN
-
Enable
Threshold
+
Enable
Comparator
UVLO
Internal
Regulator
BOOT
UVLO
Power
Stage &
Dead-time
Control
HS Switch
Current
Comparator
Oscillator
Slope
Compensation
Current
Sense
PGND
Current
Sense
BOOT
+
PGOOD
-
Threshold PGOOD Logic &
Comparator Protection
Control
Fold-back
Control
FB
VCC
AGND
I
SS
6µA
0.8V
-
+
EA
+
SW
LS Switch
Current
Comparator
SS
COMP
Fixed 5V Output Voltage
PGOOD
VIN
VCC
EN
Enable
Threshold
-
+
Enable
Comparator
UVLO
Internal
Regulator
BOOT
UVLO
Power
Stage &
Dead-time
Control
HS Switch
Current
Comparator
Oscillator
Slope
Compensation
Current
Sense
PGND
Current
Sense
BOOT
+
PGOOD
-
Logic &
Threshold
PGOOD
Protection
Comparator
Control
VS
Fold-back
Control
0.8V
VCC
AGND
I
SS
6µA
-
+
EA
+
SW
LS Switch
Current
Comparator
SS
COMP
Copyright
©
2018 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DSQ2132B-QT-01 August 2018
www.richtek.com
3
RTQ2132B-QT
Operation
Control Loop
The RTQ2132B is a high efficiency step down converter
utilizes the peak current mode control. An internal
oscillator initiates turn-on of the high-side MOSFET switch.
At the beginning of each clock cycle, the internal high-
side MOSFET switch turns on, allowing current to ramp-
up in the inductor. The inductor current is internally
monitored during each switching cycle. The output voltage
is sensed on the FB pin via the resistor divider, R1 and
R2, and compared with the internal reference voltage
(V
REF
) to generate a compensation signal (V
COMP
) on the
COMP pin. A control signal derived from the inductor
current is compared to the voltage at the COMP pin,
derived from the feedback voltage. When the inductor
current reaches its threshold, the high-side MOSFET
switch is turned off and inductor current ramps-down. While
the high-side switch is off, inductor current is supplied
through the low-side MOSFET switch. This cycle repeats
at the next clock cycle. In this way, duty-cycle and output
voltage are controlled by regulating inductor current.
Input Voltage Range
The minimum on-time, t
ON_MIN
, is the smallest duration of
time in which the high-side MOSFET switch can be in its
“on”
state. Considering the minimum on-time, the allowed
maximum input voltage, V
IN_MAX
, is calculated by :
V
OUT
V
IN_MAX
t
ON_MIN
f
SW
where the minimum on-time of the RTQ2132B is 60ns
(typically) ; f
SW
is the maximum operating frequency. The
maximum operating frequency of the RTQ2132B is
2.3MHz.
In contrast, the minimum off-time determines the allowed
minimum operating input voltage, V
IN_MIN
, to maintain the
fixed frequency operation. The minimum off-time, t
OFF_MIN
,
is the smallest amount of time that the RTQ2132B is
capable of turning on the low-side MOSFET switch, tripping
the current comparator and turning the MOSFET switch
back off. Below shows minimum off-time calculation that
considers the loss terms,
V
IN_MIN
V
OUT
+ I
OUT_MAX
R
DS(ON)_L
+ DCR
1
t
OFF_MIN
fsw
+ I
OUT_MAX
R
DS(ON)_H
R
DS(ON)_L
where the minimum off-time of the RTQ2132B is 65ns
(typically) ; R
DS(ON)_H
is the on resistance of the high-side
MOSFET switch; R
DS(ON)_L
is the on resistance of the
low-side MOSFET switch; DCR is the DC resistance of
inductor.
Maximum Duty Cycle Operation
The RTQ2132B is designed to operate in dropout at the
high duty cycle approaching 100%. If the operational duty
cycle is large and the required off time becomes smaller
than minimum off time, the RTQ2132B starts to enable
skip off time function and keeps high-side MOSFET switch
on continuously. The RTQ2132B implements skip off time
function to achieve high duty approaching 100%. Therefore,
the maximum output voltage is near the minimum input
supply voltage of the application. The input voltage at which
the devices enter dropout changes depending on the input
voltage, output voltage, switching frequency, load current,
and the efficiency of the design.
BOOT UVLO
The BOOT UVLO circuit is implemented to ensure a
sufficient voltage of BOOT capacitor for turning on the high-
side MOSFET switch at any condition. The BOOT UVLO
usually actives at extremely high conversion ratio. With
such conditions, the low-side MOSFET switch may not
have sufficient turn-on time to charge the BOOT capacitor.
The device monitors BOOT pin capacitor voltage and force
to turn on the low-side MOSFET switch when the BOOT
to SW voltage falls below V
BOOT_UVLO_L
(typically, 2.3V).
Meanwhile, the minimum off time is extended to 100ns
(typically) hence prolong the BOOT capacitor charging
time. The BOOT UVLO is sustained until the V
BOOT−SW
is
higher than V
BOOT_UVLO_H
(typically, 2.4V).
Internal Regulator
The device integrates a 5V linear regulator (V
CC
) that is
supplied by VIN and provides power to the internal circuitry.
is a registered trademark of Richtek Technology Corporation.
Copyright
©
2018 Richtek Technology Corporation. All rights reserved.
www.richtek.com
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DSQ2132B-QT-01 August 2018
RTQ2132B-QT
The internal regulator operates in low dropout mode when
V
VIN
is below 5V. The V
CC
can be used as the PGOOD
pull-up supply but it is
“NOT”
allowed to power other
device or circuitry. In many applications, a 1μF, X7R is
recommended and it needs to be placed as close as
possible to the VCC pin. Be careful to account for the
voltage coefficient of ceramic capacitors when choosing
the value and case size. Many ceramic capacitors lose
50% or more of their rated value when used near their
rated voltage.
VCC
the converter can have a monotonic smooth start-up. For
soft-start control, the SS pin should never be left
unconnected. After the SS pin voltage rises above 2V
(typically), the PGOOD pin will be in high impedance and
V
PGOOD
will be held high. The typical start-up waveform
shown in Figure 1 indicate the sequence and timing
between the output voltage and related voltage.
VIN = 12V
VIN
VCC = 5V
Enable Control
The RTQ2132B provides an EN pin, as an external chip
enable control, to enable or disable the device. If V
EN
is
held below a logic-low threshold voltage (V
IL
), switching
is inhibited even if the VIN voltage is above VIN under-
voltage lockout threshold (V
UVLO
). If V
EN
is held below
0.4V, the converter will enter into shutdown mode, that
is, the converter is disabled. During shutdown mode, the
supply current can be reduced to I
SHDN
(lower than 10μA).
If the EN voltage rises above the logic-high threshold
voltage (V
IH
) while the VIN voltage is higher than V
UVLO
,
the device will be turned on, that is, switching being enabled
and soft-start sequence being initiated. When VCC
exceeds 5V, the current source typically sinks 1.2μA for
V
EN
< 4V and up to 70μA for V
EN
> 4V.
Soft-Start
The soft-start function is used to prevent large inrush
currents while the converter is being powered up. The
RTQ2132B provides an SS pin so that the soft-start time
can be programmed by selecting the value of the external
soft-start capacitor C
SS
connected from the SS pin to
AGND. During the start-up sequence, the soft-start
capacitor is charged by an internal current source I
SS
(typically, 6μA) to generate a soft-start ramp voltage as a
reference voltage to the PWM comparator. If the output is
for some reasons pre-biased to a certain voltage during
start-up, the device will not start switching until the voltage
difference between SS pin and FB pin is larger than 400mV
( i.e. V
SS
−
V
FB
> 400mV, typically). And only when this
ramp voltage is higher than the feedback voltage V
FB
, the
switching will be resumed. The output voltage can then
ramp up smoothly to its targeted regulation voltage, and
Copyright
©
2018 Richtek Technology Corporation. All rights reserved.
EN
0.2ms
0.4 x t
SS
t
SS
2V
SS
90% x V
OUT
VOUT
PGOOD
Figure 1. Start-Up Sequence
Power Good Indication
The RTQ2132B features an open-drain power-good output
(PGOOD) to monitor the output voltage status. The output
delay of comparator prevents false flag operation for short
excursions in the output voltage, such as during line and
load transients. Pull-up PGOOD with a resistor to V
CC
or
an external voltage below 5.5V. The power-good function
is activated after soft start is finished and is controlled by
a comparator connected to the feedback signal V
FB
. If
V
FB
rises above a power-good high threshold (V
TH_PGLH1
)
(typically 90% of the reference voltage), the PGOOD pin
will be in high impedance and V
PGOOD
will be held high
after a certain delay elapsed. When V
FB
fall short of power-
good low threshold (V
TH_PGHL2
) (typically 85% of the
reference voltage) or exceeds V
TH_PGHL1
(typically 120%
of the reference voltage), the PGOOD pin will be pulled
low. For V
FB
higher than V
TH_PGHL1
, V
PGOOD
can be pulled
high again if V
FB
drops back by a power-good high
threshold (V
TH_PGLH2
) (typically 117% of the reference
voltage). Once being started-up, if any internal protection
is triggered, PGOOD will be pulled low to GND. The internal
open-drain pull-down device (1kΩ, typically) will pull the
is a registered trademark of Richtek Technology Corporation.
DSQ2132B-QT-01 August 2018
www.richtek.com
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