View RT9602_201922.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

RT9602
Dual Channel Synchronous-Rectified Buck MOSFET Driver
General Description
The RT9602 is a dual power channel MOSFET driver specifically designed to drive four power N-Channel MOSFETs in a synchronous-rectified buck converter topology. These drivers combined with RT9237/A and RT9241A/B series of Multi-Phase Buck PWM controllers provide a complete core voltage regulator solution for advanced microprocessors. The RT9602 can provide flexible gate driving for both high side and low side drivers. This gives more flexibility of MOSFET selection. The output drivers in the RT9602 have the capability to drive a 3000pF load with a 40nS propagation delay and 80nS transition time. This device implements bootstrapping on the upper gates with only a single external capacitor required for each power channel. This reduces implementation complexity and allows the use of higher performance, cost effective, NChannel MOSFETs. Adaptive shoot-through protection is integrated to prevent both MOSFETs from conducting simultaneously. The RT9602 can detect high side MOSFET drain-tosource electrical short at power on and pull the 12V power by low side MOS and cause power supply to go into over current shutdown to prevent damage of CPU.
Features
Drives Four N-Channel MOSFETs Adaptive Shoot-Through Protection Internal Bootstrap Devices Small 14-Lead SOIC Package 5V to 12V Gate-Drive Voltages for Optimal Efficiency Tri-State Input for Bridge Shutdown Supply Under-Voltage Protection Power ON Over-Voltage Protection
Applications
Core Voltage Supplies for Intel Pentium 4 and AMD AthlonTM Microprocessors High Frequency Low Profile DC-DC Converters High Current Low Voltage DC-DC Converters
Pin Configurations
Part Number RT9602CS (Plastic SOP-14)
PWM1 PWM2 GND LGATE1 PVCC PGND LGATE2
1 2 3 4 5 6 7
Pin Configurations
TOP VIEW
14 13 12 11 10 9 8
VCC PHASE1 UGATE1 BOOT1 BOOT2 UGATE2 PHASE2
Ordering Information
RT9602 Package Type S : SOP-14 Operating Temperature Range C: Commercial Standard
DS9602-02 November 2002
www.richtek.com
1
RT9602
Pin Description
Pin No. Pin Name 1 2 3 4 5 6 7 8 9 10 11 12 13 14 PWM1 PWM2 GND LGATE1 PVCC PGND LGATE2 PHASE2 UGATE2 BOOT2 BOOT1 UGATE1 PHASE1 VCC Channel 1 PWM Input Channel 2 PWM Input Ground Pin Lower Gate Drive of Channel 1 Upper and Lower Gate Driver Power Rail Lower Gate Driver Ground Pin Lower Gate Drive of Channel 2 Connect this pin to phase point of channel 2. Phase point is the connection point of high side MOSFET source and low side MOSFET drain Upper Gate Drive of Channel 2 Floating Bootstrap Supply Pin of Channel 2 Floating Bootstrap Supply Pin of Channel 1 Upper Gate Drive of Channel 1 Connect this pin to phase point of channel 1. Phase point is the connection point of high side MOSFET source and low side MOSFET drain Control Logic Power Supply Pin Function
www.richtek.com
DS9602-02 November 2002
2
RT9602
Function Block Diagram
VCC Internal 5V 40K PWM1 40K Shoot-through Protection Pow er-on OVP PVCC
BOOT1 UGATE1 PHASE1 PVCC LGATE1 PGND PVCC Shoot-through Protection Pow er-on OVP PGND BOOT2 UGATE2 PHASE2 PVCC LGATE2
Shoot-through Protection
Control Logic
Internal 5V 40K PWM2 40K Shoot-through Protection GND
PGND
DS9602-02 November 2002
www.richtek.com
3
RT9602
Absolute Maximum Ratings
Supply Voltage (VCC) Supply Voltage (PVCC) BOOT Voltage (VBOOT-VPHASE) Input Voltage (VPWM) UGATE LGATE Package Thermal Resistance SOP-14, JA Ambient Temperature Junction Temperature Storage Temperature Range Lead Temperature (Soldering, 10 sec.) ESD Level (Note) HBM MM 15V VCC + 0.3V 15V GND - 0.3V to 7V VPHASE - 0.3V to VBOOT + 0.3V GND - 0.3V to VPVCC + 0.3V 127.67C /W 0C to 70C 0C to 125C -40C to 150C 260C 2KV 200V
Electrical Characteristics
Parameter VCC Supply Current Bias Supply Current Power Supply Current Power-On Reset VCC Rising Threshold Hysteresis PWM Input Maximum Input Current PWM Floating Voltage PWM Rising Threshold PWM Falling Threshold UGATE Rise Time LGATE Rise Time UGATE Fall Time LGATE Fall Time UGATE Turn-Off Propagation Delay LGATE Turn-Off Propagation Delay Shutdown Window VPVCC = VVCC = 12V, 3nF load VPVCC = VVCC = 12V, 3nF load VPVCC = VVCC = 12V, 3nF load VPVCC = VVCC = 12V, 3nF load VVCC = VPVCC = 12V, 3nF load VVCC = VPVCC = 12V, 3nF load VPWM = 0 or 5V Vcc = 12V 80 1.1 3.3 1.0 ------1.26 127 2.1 3.7 1.26 30 30 40 30 60 45 -150 3.7 4.3 1.5 ------3.7 A V V V ns ns ns ns ns ns V 8.6 0.6 9.9 1.35 10.7 -V V IVCC IPVCC fPWM = 250kHz, VPVCC = 12V, CBOOT = 0.1F, RPHASE = 20 fPWM = 250kHz, VPVCC = 12V, CBOOT = 0.1F, RPHASE = 20 --5.5 5.5 8 10 mA mA Symbol Test Conditions Min Typ Max Units
To be continued
www.richtek.com
DS9602-02 November 2002
4
RT9602
Parameter Output Upper Drive Source Upper Drive Sink Lower Drive Source Lower Drive Sink RUGATE VVCC = 12V, VPVCC = 12V RUGATE VVCC = 12V, VPVCC = 12V RLGATE VVCC = 12V, VPVCC = 12V RLGATE VVCC = VPVCC = 12V ----1.75 2.8 1.9 1.6 3.0 5.0 3.0 3.0 Symbol Test Conditions Min Typ Max Units
Note: Devices are ESD sensitive, especially for PHASE and LGATE pins. Handling precaution recommended. The human
body model is a 100pF capacitor discharged through a 1.5K resistor into each pin.
Operation Descriptions
The RT9602 has power on protection function which held UGATE and LGATE low before VCC up cross the rising threshold voltage. After the initialization, the PWM signal takes the control. The rising PWM signal first forces the LGATE signal turns low then UGATE signal is allowed to go high just after a nonoverlapping time to avoid shoot-through current. The falling of PWM signal first forces UGATE to go low. When UGATE and PHASE signal reach a predetermined low level, LGATE signal is allowed to turn high. The non-overlapping function is also presented between UGATE and LGATE signal transient. The PWM signal is recognized as high if above rising threshold and as low if below falling threshold. Any signal level in this window is considered as tri-state, which causes turn-off of both high side and low-side MOSFET. When PWM input is floating (not connected), internal divider will pull the PWM to 1.9V to give the controller a recognizable level. The maximum sink/source capability of internal PWM reference is 60A. The PVCC pin provides flexibility of both high side and low side MOSFET gate drive voltages. If 8V, for example, is applied to PVCC, then high side MOSFET gate drive is 8V to 1.5V (approximately, internal diode plus series resistance voltage drop). The low side gate drive voltage is exactly 8V. The RT9602 implements a power on over-voltage protection function. If the PHASE voltage exceeds 1.5V at power on, the LGATE would be turn on to pull
DS9602-02 November 2002 www.richtek.com
the PHASE low until the PHASE voltage goes below 1.5V. Such function can protect the CPU from damage by some short condition happened before power on, which is sometimes encountered in the M/B manufacturing line.
5
6
+5V
www.richtek.com
RT9602
optional
1F 12V 1.2H 1000F 1F 12 PHB83N03LT 2H 3K 12 x1500F 3K 14 13 PHB95N03LT 13 PHASE1 UGATE1 PVCC 5 PGOOD 1F 10K VID4 VDD PGOOD PWM1 ISP1 ISN1 VSEN GND 15 3K 11 3K 16 2H x1500F 1F PHB83N03LT 7 1000F 1F 18 17 19 VID3 VID2 VID1 VID0 COMP FB 20 11 BOOT1 14 VCC 10 1F 12V
VID4
1
Typical Application Circuit
+5V
VID3
2
VID2
3
VID1
4
PWM1 1
2.4K
15K
VID0
5
RT9602
4 LGATE 1 PWM2 9 UGATE2 GND 2
6
66pF
7
8 ADJ
2.4K DVD SS PWM2 ISN2 ISP2 8 PHASE2
3 6 PGND LGATE 2 BOOT2 10
12V
9
18K
10
3K
0.1F
RT9241A/B
optional
PHB95N03LT
DS9602-02 November 2002
VCORE
RT9602
Application Information
Driving power MOSFETs The DC input impedance of the power MOSFET is extremely high. When Vgs at 12V (or 5V), the gate draws the current only few nanoamperes. Thus once the gate has been driven up to "ON" level, the current could be negligible. 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 also required to switch drain current on and off with the required speed. The required gate drive currents are calculated as follows.
D1 Vi d1 s1 L Vo
In Figure 1, the current Ig1 and Ig2 are required to move the gate up to 12V.The operation consists of charging Cgd and Cgs. Cgs1 and Cgs2 are the capacitances from gate to source of the high side and the low side power MOSFETs, respectively. In general data sheets, the Cgs is referred as "Ciss" which is the input capacitance. Cgd1 and Cgd2 are the capacitances 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 showed below
Igs1 = Cgs1
dV Cgs1x12 g1 = dt tr1
(1) (2)
Cgd1 Igd1 Ig1 g1 g2 Igs1
Cgs1
Igs2 = C gs2
Cgd2 d2
dVg2 dt
=
C gs1 x 12 t r2
Ig2
Igd2 D2 Igs2
Cgs2
s2 GND
According to the design of RT9602, before driving the gate of the high side MOSFET up to 12V (or 5V), the low side MOSFET has to be off; and the high side MOSFET is turned off before the low side is turned on. From Figure 1, the body diode "D2" had been turned on before high side MOSFETs turned on
I gd1 = C gd1
dV 12V = C gd1 dt t r1
(3)
Before the low side MOSFET is turned on, the Cgd2 have been charged to Vi. Thus, as Cgd2 reverses its polarity and g2 is charged up to 12V, the required current is
Igd2 = C gd2
dV Vi + 12V = C gd2 dt t r2
(4)
Figure 1. The gate driver must supply Igs to Cgs and Igd to Cgd
DS9602-02 November 2002
www.richtek.com
7
RT9602
It is helpful to calculate these currents in a typical case. Assume a synchronous rectified BUCK converter, input voltage Vi = 12V, Vg1 = Vg2 = 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
1660 x 10 -12 x 12 1.428(A) = 14 x 10 -9
2200 x 10 -12 x 12 0.88(A) = 30 x 10 -9
Vin
12V
L1
1.2 uH 1000uF
D1
R1
10 12V
C1
1uF
C2
Cb1
1uF
11 BOOT1
14 VCC PVCC 5
1uF
C7
Q1 L2 PHB83N03LT
2uH 1500uF
12 13
UGATE1 PHASE1
PWM1 1
PWM1
C5
Q2
PHB95N03LT
RT9602
4 LGATE1 PWM2 9 UGATE2 GND 8 2
PWM2
Igs1 =
(5)
C3
1000uF
3
C4
1uF
PHASE2 PGND 6
Igs 2 =
(6)
C6
1500uF
L3
2uH
Q3
PHB83N03LT
7 LGATE2 BOOT2 10
Cb2
1uF
from equation. (3) and (4)
Q4
PHB95N03LT
D2
Igd1 =
380 x 10 -12 x 12 = 0.326(A) 14 x 10 - 9
500 x 10 -12 x (12 + 12) 0.4(A) = 30 x 10 -9
(7)
VCORE
I gd2 =
(8)
Figure 2. Two- Phase Synchronous-Buck Converter Circuit
the total current required from the gate driving source is
Ig1 = Igs1 + I gd1 = (1.428 + 0.326 ) = 1.745(A) (9)
Ig2 = Igs 2 + 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. Layout Consider Figure 2. shows the schematic circuit of a two-phase synchronous-buck converter to implement the RT9602. The converter operates for the input rang from 5V to 12V.
When layout the PC board, it should be very careful. The power-circuit section is the most critical one. If not configured properly, it will generate a large amount of EMI. The junction of Q1, Q2, L2 and Q3, Q4, L4 should be very close. The connection from Q1, and Q3 drain to positive sides of C1, C2, C3, and C4; the connection from Q2, and Q4 source to the negative sides of C1, C2, C3, and C4 should be as short as possible. Next, the trace from Ugate1, Ugate2, Lgate1, and Lgate2 should also be short to decrease the noise of the driver output signals. Phase1 and phase2 signals from the junction of the power MOSFET, carrying the large gate drive current pulses, should be as heavy as the gate drive trace. The bypass capacitor C7 should be connected to PGND directly. Furthermore, the bootstrap capacitors (Cb1, Cb2) should always be placed as close to the pins of the IC as possible.
www.richtek.com
DS9602-02 November 2002
8
RT9602
Select the Bootstrap Capacitor Figure 3. shows part of the bootstrap circuit of RT9602. The VCB (the voltage difference between BOOT1 and PHASE1 on RT9602) 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 CB has to be selected properly. It is determined by following constraints.
PVCC BOOT1
+5V OR +12V
Power Dissipation For not exceeding the maximum allowable power dissipation to drive the IC beyond the maximum recommended operating junction temperature of 125C, it is necessary to calculate power dissipation appropriately. This dissipation is a function of switching frequency and total gate charge of the selected MOSFET. Figure 4. shows the power dissipation test circuit. CL and CU are the UGATE and LGATE load capacitors, respectively. The bootstrap capacitor value is 0.01F.
Vin
+
UGATE1 CB VCB
+5V OR +12V
0.01 uF
+12V UGATE1 1uF PHASE1
2N7000
PHASE1
CU
PVCC
1uF LGATE1 PWM1 CL 2N7000 33
LGATE1
0.01 uF PWM2 RT9602 UGATE2 CU PGND PHASE2 LGATE2 GND 2N7000 CL 33 2N7000
PGND
Figure 3. Part of Bootstrap Circuit of RT9602
In practice, a low value capacitor CB will lead the overcharging that could damage the IC. Therefore to minimize the risk of overcharging and reducing the ripple on VCB, the bootstrap capacitor should not be smaller than 0.1F, and the larger the better. In general design, using 1F can provide better performance. At least one low-ESR capacitor should be used to provide good local de-coupling. Here, to adopt either a ceramic or tantalum capacitor is suitable.
Figure 4. RT9602 Power Dissipation Test Circuit
Figure 5. shows the power dissipation of the RT9602 as a function of frequency and load capacitance. The value of the Cu and CL are the same and the frequency is varied from 100kHz to 600kHz. PVCC and VCC is 12V and connected together. Figure 6. shows the same characterization for PVCC tied to 5V instead of 12V.
DS9602-02 November 2002
www.richtek.com
9
RT9602
Power Dissipation vs. Frequency
800
CU=CL 700 =5nF
POWER (mW)
600 500 400 300 200 100 0 0 100 200 300 400 500 600
CU = CL=4nF CU = CL=3nF CU = CL=2nF CU= CL= 1nF PVCC = VCC = 12V
The method to improve the thermal transfer is to increase the PC board copper area around the RT9602, first. Then, adding a ground pad under IC to transfer the heat to the peripheral of the board. Power on Over-Voltage Protection Function The RT9602 provides a protect function which can avoid some short condition happened before power on. The following discussion about the power on overvoltage protection function of RT9602 is based on the experiments of the high side MOSFET directly shorted to 12V. The test circuit as shown in the typical application circuit (with RT9241A/B dual-channel synchronous-rectified buck controller) the VCC and the phase signals are measured on the VCC pin and the phase pin of RT9602. The LGATE signal is measured on the gate terminal of MOSEFET.
FREQUENCY (kHz)
Figure 5. Power Dissipation vs. Frequency (RT9602)
Power Dissipation vs. Frequency
250 240 230
CU=CL =5nF
CU = CL=4nF CU = CL=2nF
POWER(mW)
220 210 200 190 180 170 50 100 150 200 250 300 350 400 450
CU = CL=3nF
CU= CL= 1nF
VCC PHASE
PVCC = 5V, VCC = 12V
LGATE Current Through 12V 10A/Div
FREQUENCY(kHz)
Figure 6. Power Dissipation vs. Frequency, PVCC = 5V
The operating junction temperature can be calculated from the power dissipation curves (Figure 5 and Figure 6). Assume the RT9602's PVCC = VCC=12V, operating frequency is 200kHz, and the CU=CL=1.5nF which emulate the input capacitances of the high side and low side power MOSFETs. From Figure 5, the power dissipation is 500mW. In RT9602, the package thermal resistance JA is 127.67C/W, the operating junction temperature is calculated as: TJ = 127.67C/W x 500mW+ 25C = 88.84C (11)
Time (50mS) Figure 7.. High Side Direct Short
VCC
PHASE
LGATE VCORE
where the 25C is the ambient temperature.
Time (50mS) Figure 8. High Side Direct Short
www.richtek.com
DS9602-02 November 2002
10
RT9602
VCC
PHASE
LGATE PWM1
Time (25mS) Figure 9. High Side Direct Short
Referring to Figure 7, when VCC exceeds 1.5V, RT9602 turns on the LGATE to clamp the Phase through the low side MOSFET. During the turn-on of the low side MOSFET, the current of ATX 12V is limited at 25A although the maximum current of ATX 12V listed on the case of ATX is 15A. After the ATX 12V shuts down, the VCC falls slowly. Please note that the trigger point of RT9602 is at 1.5V VCC, and the clamped value of phase is at about 2.4V. Next, reference to Figure 8, it is obvious that since the Phase voltage increases during the power-on, the VCORE increases correspondingly, but is gradually decreased as LGATE and VCC decrease. In Figure 9, during the turn-on of the low side MOSFET, the VCC is much less than 12V, thus the RT9241A/B keeps the PWM signal at high impedance state.
DS9602-02 November 2002
www.richtek.com
11
RT9602
Package Information
H M
B
B
J
A C F D
I
Symbol A B C D F H I J M
Dimensions In Millimeters Min 8.534 3.810 1.346 0.330 1.194 0.178 0.102 5.791 0.406 Max 8.738 3.988 1.753 0.508 1.346 0.254 0.254 6.198 1.270
Dimensions In Inches Min 0.336 0.150 0.053 0.013 0.047 0.007 0.004 0.228 0.016 Max 0.344 0.157 0.069 0.020 0.053 0.010 0.010 0.244 0.050
14-Lead SOP Plastic Package
www.richtek.com
DS9602-02 November 2002
12
RT9602
DS9602-02 November 2002
www.richtek.com
13
RT9602
RICHTEK TECHNOLOGY CORP.
Headquarter
5F, No. 20, Taiyuen Street, Chupei City Hsinchu, Taiwan, R.O.C. Tel: (8863)5526789 Fax: (8863)5526611
RICHTEK TECHNOLOGY CORP.
Taipei Office (Marketing)
8F-1, No. 137, Lane 235, Paochiao Road, Hsintien City Taipei County, Taiwan, R.O.C. Tel: (8862)89191466 Fax: (8862)89191465 Email: marketing@richtek.com
www.richtek.com
DS9602-02 November 2002
14

▲Up To Search▲

Price & Availability of RT9602

	To Download RT9602 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .