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TIMER
OUTPUT-VOLTAGE SLEW-RATE CONTROL
dVs
dt
+
15 mA
C
gd
(1)
VREG CAPACITOR
GATE DRIVE CIRCUITRY
SLVS265G – FEBRUARY 2000 – REVISED NOVEMBER 2006
APPLICATION INFORMATION (continued)
Table 3. Some Available N-Channel MOSFETs
CURRENT RANGE
PART NUMBER
DESCRIPTION
MANUFACTURER
(A)
IRF7601
N-channel, rDS(on) = 0.035 , 4.6 A, Micro-8
International Rectifier
MTSF3N03HDR2
N-channel, rDS(on) = 0.040 , 4.6 A, Micro-8
ON Semiconductor
0 to 2
IRF7101
Dual N-channel, rDS(on) = 0.1 , 2.3 A, SO-8
International Rectifier
MMSF5N02HDR2
Dual N-channel, rDS(on) = 0.04 , 5 A, SO-8
ON Semiconductor
IRF7401
N-channel, rDS(on) = 0.022 , 7 A, SO-8
International Rectifier
MMSF5N02HDR2
N-channel, rDS(on) = 0.025 , 5 A, SO-8
ON Semiconductor
2 to 5
IRF7313
Dual N-channel, rDS(on) = 0.029 , 5.2 A, SO-8
International Rectifier
SI4410
N-channel, rDS(on) = 0.020 , 8 A, SO-8
Vishay Dale
IRLR3103
N-channel, rDS(on) = 0.019 , 29 A, d-Pak
International Rectifier
5 to 10
IRLR2703
N-channel, rDS(on) = 0.045 , 14 A, d-Pak
International Rectifier
For most applications, a minimum capacitance of 50 pF is recommended to prevent false triggering. This
capacitor should be connected between TIMER and ground. The presence of an overcurrent condition on either
channel of the TPS2300/01 causes a 50-
A current source to begin charging this capacitor. If the overcurrent
condition persists until the capacitor has been charged to approximately 0.5 V, the TPS2300/01 latches off the
offending channels and pulls the FAULT pin low. The timer capacitor can be made as large as desired to
provide additional time delay before registering a fault condition. The time delay is approximately:
dt(sec) = CTIMER(F) × 10,000().
When enabled, the TPS2300/01 controllers supply the gates of each external MOSFET transistor with a current
of approximately 15
A. The slew rate of the MOSFET source voltage is thus limited by the gate-to-drain
capacitance Cgd of the external MOSFET capacitor to a value approximating:
If a slower slew rate is desired, an additional capacitance can be connected between the gate of the external
MOSFET and ground.
The internal voltage regulator connected to VREG requires an external capacitor to ensure stability. A 0.1-
F or
0.22-
F ceramic capacitor is recommended.
The TPS2300/01 includes four separate features associated with each gate-drive terminal:
A charging current of approximately 15 A is applied to enable the external MOSFET transistor. This current
is generated by an internal charge pump that can develop a gate-to-source potential (referenced to DISCH1
or DISCH2) of 9 V–12 V. DISCH1 and DISCH2 must be connected to the respective external MOSFET
source terminals to ensure proper operation of this circuitry.
A discharge current of approximately 75 A is applied to disable the external MOSFET transistor. Once the
transistor gate voltage has dropped below approximately 1.5 V, this current is disabled and the UVLO
discharge driver is enabled instead. This feature allows the part to enter a low-current shutdown mode while
ensuring that the gates of the external MOSFET transistors remain at a low voltage.
During a UVLO condition, the gates of both MOSFET transistors are pulled down by internal PMOS
transistors. These transistors continue to operate even if IN1 and IN2 are both at 0 V. This circuitry also
helps hold the external MOSFET transistors off when power is suddenly applied to the system.
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