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PDF RT9612A Data sheet ( Hoja de datos )
| Número de pieza | RT9612A | |
| Descripción | Synchronous-Rectified Buck MOSFET Driver | |
| Fabricantes | Richtek | |
| Logotipo |  |
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®
RT9612A/B
Synchronous-Rectified Buck MOSFET Driver
General Description
The RT9612A/B is a high frequency, synchronous rectified,
single phase dual MOSFET driver designed to adapt from
normal MOSFET driving applications to high performance
CPU VR driving capabilities.
The RT9612A/B can be utilized under both VCC = 5V or
VCC = 12V applications. The RT9612A/B also builds in an
internal power switch to replace external boot strap diode.
The RT9612A/B can support switching frequency efficiently
up to 500kHz. The RT9612A/B has the UGATE driving
circuit and the LGATE driving circuit for synchronous
rectified DC/DC converter applications. The driving rise/
fall time capability is designed within 30ns and the shoot
through protection mechanism is designed to prevent shoot
through of high side and low side power MOSFETs. The
RT9612A/B has PWM tri-state shut down function which
can force driver output into high impedance.
The difference of the RT9612A and the RT9612B is the
propagation delay, tUGATEpdh. The RT9612B has
comparatively large tUGATEpdh than RT9612B. Hence, the
RT9612A is usually recommended to be utilized in
performance oriented applications, such as high power
density CPU VR or GPU VR. The RT9612A/B comes in a
small footprint with SOP-8, SOP-8 (Exposed Pad) and
WDFN-8EL 3x3.
Features
Drive Two N-MOSFETs
Adaptive Shoot Through Protection
Embedded Bootstrap Diode
Support High Switching Frequency
Fast Output Rise Time
Tri-State Input for Bridge Shutdown
Small SOP-8, SOP-8 (Exposed Pad) and 8-Lead
WDFN Packages
RoHS Compliant and Halogen Free
Applications
Core Voltage Supplies for Desktop, Motherboard CPU
High Frequency Low Profile DC/DC Converters
High Current Low Voltage DC/DC Converters
Ordering Information
RT9612A/B
Package Type
S : SOP-8
SP : SOP-8 (Exposed Pad-Option1)
QW : WDFN-8EL 3x3 (W-Type)
Lead Plating System
G : Green (Halogen Free and Pb Free)
Z : ECO (Ecological Element with
Halogen Free and Pb free)
Note :
Long Dead Time
Short Dead Time
Richtek products are :
` 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.
Copyright ©2012 Richtek Technology Corporation. All rights reserved.
DS9612A/B-03 June 2012
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
1
1 page  
RT9612A/B
Absolute Maximum Ratings (Note 1)
Supply Voltage, VCC -------------------------------------------------------------------------------- −0.3V to 15V
BOOT to PHASE ------------------------------------------------------------------------------------- −0.3V to 15V
PHASE to GND
DC ------------------------------------------------------------------------------------------------------- −5V to 15V
< 200ns ------------------------------------------------------------------------------------------------ −10V to 30V
LGATE
DC ------------------------------------------------------------------------------------------------------- (GND − 0.3V) to (VCC + 0.3V)
< 200ns ------------------------------------------------------------------------------------------------ −2V to (VCC + 0.3V)
UGATE -------------------------------------------------------------------------------------------------- (VPHASE − 0.3V) to (VBOOT + 0.3V)
< 200ns ------------------------------------------------------------------------------------------------ (VPHASE − 2V) to (VBOOT + 0.3V)
PWM Input Voltage ---------------------------------------------------------------------------------- (GND − 0.3V) to 7V
Power Dissipation, PD @ TA = 25°C
SOP-8 --------------------------------------------------------------------------------------------------- 0.833W
SOP-8 (Exposed Pad) ------------------------------------------------------------------------------ 1.333W
WDFN-8EL 3x3 --------------------------------------------------------------------------------------- 1.429W
Package Thermal Resistance (Note 2)
SOP-8, θJA --------------------------------------------------------------------------------------------- 120°C/W
SOP-8 (Exposed Pad), θJA ------------------------------------------------------------------------- 75°C/W
SOP-8 (Exposed Pad), θJC ------------------------------------------------------------------------ 15°C/W
WDFN-8EL 3x3, θJA ---------------------------------------------------------------------------------- 70°C/W
WDFN-8EL 3x3, θJC --------------------------------------------------------------------------------- 8.2°C/W
Lead Temperature (Soldering, 10 sec.) ---------------------------------------------------------- 260°C
Junction Temperature -------------------------------------------------------------------------------- 150°C
Storage Temperature Range ----------------------------------------------------------------------- −65°C to 150°C
ESD Susceptibility (Note 3)
HBM (Human Body Model) ------------------------------------------------------------------------- 2kV
Recommended Operating Conditions (Note 4)
Supply Voltage, VCC -------------------------------------------------------------------------------- 12V ± 10%
Junction Temperature Range ----------------------------------------------------------------------- −40°C to 125°C
Ambient Temperature Range ----------------------------------------------------------------------- −40°C to 85°C
Copyright ©2012 Richtek Technology Corporation. All rights reserved.
DS9612A/B-03 June 2012
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
5
5 Page 
RT9612A/B
BOOT
VIN
UGATE
PHASE
VCC
CB
LGATE
GND
+
VCB
-
Figure 2. Part of Bootstrap Circuit of RT9612A/B
In practice, a low value capacitor CB will lead to the over
charging that could damage the IC. Therefore, to minimize
the risk of overcharging and to reduce the ripple on VCB,
the bootstrap capacitor should not be smaller than 0.1μF,
and the larger the better. In general design, using 1μF can
provide better performance. At least one low-ESR capacitor
should be used to provide good local de-coupling. It is
recommended to adopt a ceramic or tantalum capacitor.
Power Dissipation
To prevent driving the IC beyond the maximum
recommended operating junction temperature of 125°C,
it is necessary to calculate the power dissipation
appropriately. This dissipation is a function of switching
frequency and total gate charge of the selected MOSFET.
Figure 3 shows the power dissipation test circuit. CL and
CU are the UGATE and LGATE load capacitors,
respectively. The bootstrap capacitor value is 1μF.
10
12V
CBOOT
1µF
12V
1µF
PWM
BOOT
VCC UGATE
RT9612A/B
PHASE
PWN LGATE
GND
2N7002
CU
3nF
2N7002
CL
3nF
20
Figure 3. Test Circuit
Figure 4 shows the power dissipation of the RT9612A/B
as a function of frequency and load capacitance. The value
of CU and CL are the same and the frequency is varied
from 100kHz to 1MHz.
Power Dissipation vs. Frequency
1000
900
800 CU = CL = 3nF
700
600
CU = CL = 2nF
500
400
300
200 CU = CL = 1nF
100
0
0 200 400 600 800 1000
Frequency (kHz)
Figure 4. Power Dissipation vs. Frequency
The operating junction temperature can be calculated from
the power dissipation curves (Figure 4). Assume
VCC = 12V, operating frequency is 200kHz and CU = CL =
1nF which emulate the input capacitances of the high side
and low side power MOSFETs. From Figure 4, the power
dissipation is 100mW. Thus, for example, with the SOP-
8 package, the package thermal resistance θJA is 120°C/
W. The operating junction temperature is then calculated
as :
TJ = (120°C/W x 100mW) + 25°C = 37°C
where the ambient temperature is 25°C.
(11)
Thermal Considerations
For recommended operating condition specifications, the
maximum junction temperature is 125°C. The junction to
ambient thermal resistance, θJA, is layout dependent. For
SOP-8 packages, the thermal resistance, θJA, is
120°C/W on a standard JEDEC 51-7 four-layer thermal
test board. For SOP-8 (Exposed Pad) packages, the
thermal resistance, θJA, is 75°C/W on a standard JEDEC
51-7 four-layer thermal test board. For WDFN-8EL 3x3
packages, the thermal resistance, θJA, is 70°C/W on a
Copyright ©2012 Richtek Technology Corporation. All rights reserved.
DS9612A/B-03 June 2012
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
11
11 Page | ||
| Páginas | Total 15 Páginas | |
| PDF Descargar | [ Datasheet RT9612A.PDF ] | |
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