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PDF RT8231A Data sheet ( Hoja de datos )
| Número de pieza | RT8231A | |
| Descripción | Complete DDR Memory Power Supply Controller | |
| Fabricantes | RICHTEK | |
| Logotipo |  |
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®
RT8231A/B
Complete DDR Memory Power Supply Controller
General Description
The RT8231A/B provides a complete power supply for
DDR2/DDR3/DDR3L/LPDDR3/DDR4 memory systems. It
integrates a synchronous PWM Buck controller with a
1.5A sink/source tracking linear regulator and buffered low
noise reference.
The PWM controller provides the low quiescent current,
high efficiency, excellent transient response, and high DC
output accuracy needed for stepping down high-voltage
batteries to generate low-voltage chipset RAM supplies
in notebook computers. The constant on-time PWM
control scheme handles wide input/output voltage ratios
with ease and provides 100ns “instant-on” response to
load transients while maintaining a relatively constant
switching frequency.
The RT8231A/B achieves high efficiency at a reduced cost
by eliminating the current-sense resistor found in
traditional current mode PWMs. Efficiency is further
enhanced by its ability to drive very large synchronous
rectifier MOSFETs. The Buck conversion allows this device
to directly step down high-voltage batteries for the highest
possible efficiency.
The 1.5A sink/source LDO maintains fast transient
response only requiring a 10μF ceramic output capacitor.
In addition, the LDO supply input is available externally
to significantly reduce the total power losses. The
RT8231A/B supports all of the sleep state controls placing
VTT at high-Z in S3 and discharging VDDQ, VTT and
VTTREF (soft-off) in S4/S5.
The RT8231A/B provides protections including OVP, UVP,
and thermal shutdown. The RT8231A/B is available in the
WQFN-20L 3x3 package.
Applications
DDR2/DDR3/DDR3L/LPDDR3/DDR4 Memory Power
Supplies
Notebook computers
SSTL18, SSTL15 and HSTL bus termination
Pin Configurations
(TOP VIEW)
VTTGND
VTTSNS
GND
VTTREF
VDDQ
20 19 18 17 16
1 15 LGATE
2 14 PGND
3
GND
13 CS
4 21 12 VDD
5 11 VID
6 7 8 9 10
WQFN-20L 3x3
Simplified Application Circuit
VVDD
PGOOD
VTT
VDD
TON
RT8231A/B
UGATE
PGOOD
BOOT
VTT
VTTSNS
PHASE
LGATE
CS FB
VTTREF
S3
S5 VDDQ
VID GND VLDOIN
VIN
VVDDQ
Copyright ©2015 Richtek Technology Corporation. All rights reserved.
DS8231A/B-05 March 2015
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
1
1 page  
Operation
The RT8231A/B is a constant on-time synchronous step-
down controller. In normal operation, the high-side
N-MOSFET is turned on when the output voltage is lower
than VREF, and is turned off after the internal one-shot
timer expires. While the high-side N-MOSFET is turned
off, the low-side N-MOSFET is turned on to conduct the
inductor current until next cycle begins.
Soft-Start (SS)
For internal soft-start function, an internal current source
charges an internal capacitor to build the soft-start ramp
voltage. The output voltage will track the internal ramp
voltage during soft-start interval.
PGOOD
The power good output is an open-drain architecture. When
the soft-start is finished, the PGOOD open-drain output
will be high impedance.
Current Limit
The current limit circuit employs a unique “valley” current
sensing algorithm. If the magnitude of the current sense
signal at PHASE is above the current limit threshold, the
PWM is not allowed to initiate a new cycle. The current
limit threshold can be set with an external voltage setting
resistor on the CS pin.
RT8231A/B
Over-Voltage Protection (OVP) & Under-Voltage
Protection (UVP)
The output voltage is continuously monitored for over-
voltage and under-voltage protection. When the output
voltage exceeds its set voltage threshold( 115% of VOUT),
UGATE goes low and LGATE is forced high. When the
feedback voltage is less than 0.45V, under-voltage
protection is triggered and then both UGATE and LGATE
gate drivers are forced low. The controller is latched until
VDD is re-supplied and exceeds the POR rising threshold
voltage or S5 is reset.
VTT Linear Regulator and VTTREF
This VTT linear regulator employs ultimate fast response
feedback loop so that small ceramic capacitors are enough
for keeping track of VTTREF within 40mV at all conditions,
including fast load transient. The VTTREF block consists
of on-chip 1/2 divider, LPF and buffer. This regulator also
has sink and source capability up to 10mA. Bypass
VTTREF to GND with a 33nF ceramic capacitor for stable
operation.
Copyright ©2015 Richtek Technology Corporation. All rights reserved.
DS8231A/B-05 March 2015
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
5
5 Page 
Typical Operating Characteristics
Switching Frequency vs. Load Current
500
450
DDR3L, VIN = 7.4V, VDDQ = 1.35V,
S3 = GND, S5 = 5V, RTON = 620kΩ
400
350
300
250
200
150
100
50
0
0.01
0.1 1
Load Current (A)
10
Switching Frequency vs. Load Current
500
DDR3L, VIN = 19V, VDDQ = 1.35V,
450 S3 = GND, S5 = 5V, RTON = 620kΩ
400
350
300
250
200
150
100
50
0
0.01
0.1 1
Load Current (A)
10
Switching Frequency vs. Load Current
500
DDR4, VIN = 12V, VDDQ = 1.2V,
450 S3 = GND, S5 = 5V, RTON = 620kΩ
400
350
300
250
200
150
100
50
0
0.01
0.1 1
Load Current (A)
10
Copyright ©2015 Richtek Technology Corporation. All rights reserved.
DS8231A/B-05 March 2015
RT8231A/B
Switching Frequency vs. Load Current
500
450
DDR3L, VIN = 12V, VDDQ = 1.35V,
S3 = GND, S5 = 5V, RTON = 620kΩ
400
350
300
250
200
150
100
50
0
0.01
0.1 1
Load Current (A)
10
Switching Frequency vs. Load Current
500
450
DDR4, VIN = 7.4V, VDDQ = 1.2V,
S3 = GND, S5 = 5V, RTON = 620kΩ
400
350
300
250
200
150
100
50
0
0.01
0.1 1
Load Current(A)
10
Switching Frequency vs. Load Current
500
450
DDR4, VIN = 19V, VDDQ = 1.2V,
S3 = GND, S5 = 5V, RTON = 620kΩ
400
350
300
250
200
150
100
50
0
0.01
0.1 1
Load Current (A)
10
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
11
11 Page | ||
| Páginas | Total 23 Páginas | |
| PDF Descargar | [ Datasheet RT8231A.PDF ] | |
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