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PDF RT9624E Data sheet ( Hoja de datos )
| Número de pieza | RT9624E | |
| Descripción | Single Phase Synchronous Rectified Buck MOSFET Driver | |
| Fabricantes | Richtek | |
| Logotipo |  |
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RT9624E
Single Phase Synchronous Rectified Buck MOSFET Driver
General Description
The RT9624E is a high frequency, synchronous rectified,
single phase MOSFET driver designed for normal MOSFET
driving applications and high performance CPU VR driving
capabilities.
The RT9624E can be supplied from 4.5V to 13.2V. The
applicable power stage VIN range is from 5V to 24V. The
RT9624E also builds in an internal power switch to replace
external bootstrap diode.
The RT9624E can support switching frequency efficiently
up to 500kHz. The RT9624E has both UGATE and LGATE
driving circuits for synchronous rectified DC/DC converter
applications. The shoot through protection mechanism is
designed to prevent shoot through between high-side and
low-side power MOSFETs. The RT9624E has tri-state
PWM input with shutdown and EN input shutdown
functions, which can force driver to output low UGATE
and LGATE signals.
The RT9624E is available in a small footprint WDFN-8L
3x3 package.
Features
z Drive Two N-MOSFETs
z Shoot Through Protection
z Embedded Bootstrap Diode
z Support High Switching Frequency
z Fast Output Rising Time
z Tri-State PWM Input for Output Shutdown
z Enable Control
z 8-Lead WDFN Package
z RoHS Compliant and Halogen Free
Applications
z Core Voltage Supplies for Desktop, Motherboard CPU
z High Frequency Low Profile DC/DC Converters
z High Current Low Voltage DC/DC Converters
z Core Voltage Supplies for GFX Card
Marking Information
4Q= : Product Code
4Q=YM
DNN
YMDNN : Date Code
Simplified Application Circuit
R1
12V
C1
Chip Enable
PWM
Controller
RT9624E
VCC
BOOT
R2
UGATE
EN PHASE
PWM LGATE
GND
CBOOT
R3
R4
C5 C6
VIN
Q1
L1
VOUT
R5
Q2
C2
C3 C4
Copyright ©2014 Richtek Technology Corporation. All rights reserved.
DS9624E-00 January 2014
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
1
1 page  
RT9624E
Absolute Maximum Ratings (Note 1)
z Supply Voltage, VCC -------------------------------------------------------------------------------- −0.3V to 15V
z BOOT to PHASE ------------------------------------------------------------------------------------- −0.3V to 15V
z PHASE to GND
DC -------------------------------------------------------------------------------------------------------- −0.3V to 30V
< 20ns --------------------------------------------------------------------------------------------------- −10V to 35V
z LGATE to GND
DC -------------------------------------------------------------------------------------------------------- −0.3V to (VCC + 0.3V)
< 20ns --------------------------------------------------------------------------------------------------- −2V to (VCC + 0.3V)
z UGATE to GND
DC -------------------------------------------------------------------------------------------------------- (VPHASE − 0.3V) to (VBOOT + 0.3V)
< 20ns --------------------------------------------------------------------------------------------------- (VPHASE − 2V) to (VBOOT + 0.3V)
z EN, PWM to GND ------------------------------------------------------------------------------------ −0.3V to 7V
z Power Dissipation, PD @ TA = 25°C
WDFN-8L 3x3 ----------------------------------------------------------------------------------------- 3.22W
z Package Thermal Resistance (Note 2)
WDFN-8L 3x3, θJA ------------------------------------------------------------------------------------ 31°C/W
WDFN-8L 3x3, θJC ------------------------------------------------------------------------------------ 8°C/W
z Lead Temperature (Soldering, 10 sec.) ---------------------------------------------------------- 260°C
z Junction Temperature -------------------------------------------------------------------------------- 150°C
z Storage Temperature Range ----------------------------------------------------------------------- −65°C to 150°C
z ESD Susceptibility (Note 3)
HBM (Human Body Model) ------------------------------------------------------------------------- 2kV
Recommended Operating Conditions (Note 4)
z Supply Voltage, VCC -------------------------------------------------------------------------------- 4.5V to 13.2V
z Input Voltage, (VIN + VCC) ------------------------------------------------------------------------- < 35V
z Junction Temperature Range ----------------------------------------------------------------------- −40°C to 125°C
z Ambient Temperature Range ----------------------------------------------------------------------- −40°C to 85°C
Copyright ©2014 Richtek Technology Corporation. All rights reserved.
DS9624E-00 January 2014
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
5
5 Page 
RT9624E
d1
VIN
Cgd1
D1
s1
Cgs1
VPHASE L
VOUT
Igd1 Igs1
Ig1
g1 g2
Ig2 Igd2
Igs2
Cgd2
d2
D2
Cgs2 s2
Vg1
VPHASE +12V
GND
Vg2 12V
t
t
Figure 1. Equivalent Circuit and Waveforms (VCC = 12V)
In Figure 1, the current Ig1 and Ig2 are required to move the
gate up to 12V. The operation consists of charging Cgd1,
Cgd2 , Cgs1 and Cgs2. Cgs1 and Cgs2 are the capacitors from
gate to source of the high-side and the low-side power
MOSFETs, respectively. In general data sheets, the Cgs1
and Cgs2 are referred as “Ciss” which are the input
capacitors. Cgd1 and Cgd2 are the capacitors from gate to
drain of the high-side and the low-side power MOSFETs,
respectively and referred to the data sheets as “Crss” the
reverse transfer capacitance. For example, tr1 and tr2 are
the rising time of the high-side and the low-side power
MOSFETs respectively, the required current Igs1 and Igs2,
are shown as below :
dVg1 Cgs1 x 12
Igs1 = Cgs1 dt =
tr1
(1)
dVg2 Cgs1 x 12
Igs2 = Cgs1 dt =
tr2
(2)
Before driving the gate of the high-side MOSFET up to
12V, the low-side MOSFET has to be off; and the high-
side MOSFET will be turned off before the low-side is
turned on. From Figure 1, the body diode “D2” will be
turned on before high-side MOSFETs turn on.
Copyright ©2014 Richtek Technology Corporation. All rights reserved.
DS9624E-00 January 2014
Igd1
= Cgd1
dV
dt
= Cgd1
12
tr1
(3)
Before the low-side MOSFET is turned on, the Cgd2 have
been charged to VIN. Thus, as Cgd2 reverses its polarity
and g2 is charged up to 12V, the required current is
Igd2
= Cgd2
dV
dt
=
Cgd2
VIN + 12
tr2
(4)
It is helpful to calculate these currents in a typical case.
Assume a synchronous rectified Buck converter, input
voltage VIN = 12V, Vgs1 = 12V, Vgs2 = 12V. The high-side
MOSFET is PHB83N03LT whose Ciss = 1660pF,
Crss = 380pF, and tr = 14ns. The low-side MOSFET is
PHB95N03LT whose Ciss = 2200pF, Crss = 500pF and
tr = 30ns, from the equation (1) and (2) we can obtain
Igs1
= 1660 x 10-12 x 12
14 x 10-9
= 1.428
(A)
(5)
Igs2
= 2200 x 10-12 x 12 = 0.88
30 x 10-9
(A)
(6)
from equation. (3) and (4)
Igd1
=
380 x 10-12 x 12
14 x 10-9
= 0.326
(A)
500 x 10-12 x (12+12)
Igd2 =
30 x 10-9
= 0.4 (A)
(7)
(8)
the total current required from the gate driving source can
be calculated as the following equations.
Ig1 = Igs1 + Igd1 = (1.428 + 0.326) = 1.754 (A)
Ig2 = Igs2 + Igd2 = (0.88 + 0.4) = 1.28 (A)
(9)
(10)
By a similar calculation, we can also get the sink current
required from the turned off MOSFET.
Select the Bootstrap Capacitor
Figure 2 shows part of the bootstrap circuit of the
RT9624E. The VCB (the voltage difference between BOOT
and PHASE on RT9624E) provides a voltage to the gate
of the high-side power MOSFET. This supply needs to be
ensured that the MOSFET can be driven. For this, the
capacitance CBOOT has to be selected properly. It is
determined by the following constraints.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
11
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet RT9624E.PDF ] | |
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