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PDF RT9625A Data sheet ( Hoja de datos )
| Número de pieza | RT9625A | |
| Descripción | Dual-Channel Synchronous Rectified MOSFET Driver | |
| Fabricantes | Richtek | |
| Logotipo |  |
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®
RT9625A
Dual-Channel Synchronous Rectified MOSFET Driver
General Description
The RT9625A is a high frequency, synchronous rectified,
two phase MOSFET driver designed for normal MOSFET
driving applications and high performance CPU VR driving
capabilities.
The RT9625A can be supplied from 4.5V to 13.2V. The
applicable power stage VIN range is from 5V to 23V. The
RT9625A also builds in internal power switches to replace
external bootstrap diodes.
The RT9625A can support switching frequency efficiently
up to 500kHz. The RT9625A has the 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 RT9625A has tri-state PWM
input with shutdown and EN shutdown functions, which
can force driver to output low UGATE and LGATE signals.
The RT9625 comes in a small footprint with WQFN-16L
4x4 package.
Features
z Drive Four N-MOSFETs for Two-Phase PWM Control
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 Small 16-Lead WQFN 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
06 : Product Code
06 YM
DNN
YMDNN : Date Code
Simplified Application Circuit
12V
PWM1
PWM2
Chip Enable
VCC
RT9625A
PWM1 PHASE1
PWM2
EN1
EN2 PHASE2
GND
VIN
L1
VOUT
L2
Copyright ©2013 Richtek Technology Corporation. All rights reserved.
DS9625A-03 June 2013
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
1
1 page  
RT9625A
Absolute Maximum Ratings (Note 1)
z Supply Voltage, VCC -------------------------------------------------------------------------------- −0.3V to 15V
z BOOTx to PHASEx ---------------------------------------------------------------------------------- −0.3V to 15V
z PHASEx to GND
DC -------------------------------------------------------------------------------------------------------- −0.3V to 30V
< 20ns --------------------------------------------------------------------------------------------------- −10V to 35V
z LGATEx to GND
DC -------------------------------------------------------------------------------------------------------- −0.3V to (VCC + 0.3V)
< 20ns --------------------------------------------------------------------------------------------------- −2V to (VCC + 0.3V)
z UGATEx to GND
DC -------------------------------------------------------------------------------------------------------- (VPHASE − 0.3V) to (VBOOT + 0.3V)
< 20ns --------------------------------------------------------------------------------------------------- (VPHASE − 2V) to (VBOOT + 0.3V)
z ENx, PWMx to GND --------------------------------------------------------------------------------- −0.3V to 7V
z POR to GND ------------------------------------------------------------------------------------------- −0.3V to 5V
z Power Dissipation, PD @ TA = 25°C
WQFN-16L 4x4 --------------------------------------------------------------------------------------- 1.852W
z Package Thermal Resistance (Note 2)
WQFN-16L 4x4, θJA ---------------------------------------------------------------------------------- 54°C/W
WQFN-16L 4x4, θJC --------------------------------------------------------------------------------- 7°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
Electrical Characteristics
(VCC = 12V, TA = 25°C unless otherwise specified)
Parameter
Symbol
Test Conditions
Power Supply Voltage
VCC
Power Supply Current
IVCC
VBOOTx = 12V, PWMx Floating
Power On Reset (POR)
POR Rising Threshold
VPOR_r
VCC Rising
POR Falling Threshold
VPOR_f
VCC Falling
POR Pin High Voltage
VPOR_H
POR Pin Low Voltage
VPOR_L
Min Typ Max Unit
4.5 -- 13.2 V
-- 180 -- μA
-- 4 4.4 V
3 3.5 --
V
-- 3.5 4
V
-- -- 0.5 V
Copyright ©2013 Richtek Technology Corporation. All rights reserved.
DS9625A-03 June 2013
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
5
5 Page 
RT9625A
However, the capacitance at the gate to source terminal
should be considered. It requires relatively large currents
to drive the gate up and down 12V (or 5V) rapidly. It is
also required to switch drain current on and off with the
required speed. The required gate drive currents are
calculated as follows.
d1
VIN
Cgd1
s1
Cgs1
VPHASEx
L
VOUT
Igd1 Igs1
Ig1
g1 g2
Ig2 Igd2
Igs2
Cgd2
d2
D2
Cgs2 s2
Vg1
VPHASEx +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)
Copyright ©2013 Richtek Technology Corporation. All rights reserved.
DS9625A-03 June 2013
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.
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)
(7)
500 x 10-12 x (12+12)
Igd2 =
30 x 10-9
= 0.4 (A)
(8)
the total current required from the gate driving source can
be calculated as following equations.
Ig1 = Igs1 + Igd1 = (1.428 + 0.326) = 1.754 (A)
(9)
Ig2 = Igs2 + Igd2 = (0.88 + 0.4) = 1.28 (A)
(10)
By a similar calculation, we can also get the sink current
required from the turned off MOSFET.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
11
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet RT9625A.PDF ] | |
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