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MAX4959 Datasheet(PDF) 5 Page - Maxim Integrated Products |
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MAX4959 Datasheet(HTML) 5 Page - Maxim Integrated Products |
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Detailed Description The MAX4959/MAX4960 provide up to +28V overvoltage protection for low-voltage systems. When the input volt- age exceeds the overvoltage trip level, the MAX4959/ MAX4960 turn off an external pFET to prevent damage to the protected components. The MAX4959/MAX4960 feature a control bit (CB) pin that controls an external battery-switchover function that switches in the battery when the adapter is unconnect- ed. The host system detects when the battery switchover must take place and pulls CB high to turn on P2. The load current is not interrupted during battery switchover as the body diode of P2 conducts until the CB line is dri- ven high (see the MAX4959 Typical Operating Circuit 1, Figure 4). An additional safety feature latches off pFET P1 when a low-power adapter is plugged in. This protects the sys- tem from seeing repeated adapter insertions and removals when an incorrect low-power adapter is plugged in that cannot provide sufficient current. Undervoltage Lockout (UVLO) The MAX4959/MAX4960 have an adjustable undervolt- age lockout threshold ranging from +5V to +28V. When VIN is less than the VUVLO, the device waits for a blank- ing time, tBLANK, to see if the fault still exists. If the fault does not exist at the end of tBLANK, P1 remains on. If VIN is less than VUVLO for longer than the blanking time, the device turns P1 off and P1 does not turn on again until VIN < 0.75V. See Figure 1. Overvoltage Lockout (OVLO) The MAX4959/MAX4960 have an adjustable overvolt- age lockout threshold ranging from +6V to +28V. When VIN is greater than the VOVLO, the device turns P1 off immediately. When VIN drops below VOVLO, P1 turns on again after the debounce time has elapsed. Device Operation High-Voltage Adapter (VIN > VOVLO) If an adapter with a voltage higher than VOVLO is plugged in, the MAX4959/MAX4960 is in an OVP condi- tion, so P1 is kept off or immediately turned off. There is High-Voltage OVP with Battery Switchover _______________________________________________________________________________________ 5 Pin Description PIN MAX4959 MAX4960 NAME FUNCTION 1 1 GATE1 pFET Gate Drive Output Open Drain. GATE1 is actively driven low, except during fault (OVP or UVP) condition (the external PFET is turned off). When VUVLO < VIN < VOVLO, GATE1 is driven low (the external PFETP1 is turned on). 2, 9 9 N.C. No Connection. Not internally connected. (Connect to ground or leave unconnected.) —2 SOURCE1 pFET Source Output. An internal resistor is connected between SOURCE1 and GATE1. 33 IN Voltage Input. IN is both the power-supply input and the overvoltage/undervoltage sense input. Bypass IN to GND with a 1µF ceramic capacitor to get a ±15kV protected input. A minimum 0.1µF ceramic capacitor is required for proper operation. 4 4 UVS Undervoltage Threshold Set Input. Connect UVS to an external resistive divider from IN to GND to set the undervoltage lockout threshold. (See Typical Operating Circuits.) 5 5 OVS Overvoltage Threshold Set Input. Connect OVS to an external resistive divider from IN to GND to set the overvoltage lockout threshold. (See Typical Operating Circuits.) 66 VDD Internal Power-Supply Output. Bypass VDD to GND with a 0.1µF minimum capacitor. VDD powers the internal power-on reset circuits. (See the VDD Capacitor Selection section.) 77 CB Battery Switchover Control Input. When CB is high, GATE1 is high (P1 is off), and GATE2 is low (P2 is on). When CB is low, GATE1 is controlled by internal logic and GATE2 is high (P2 is off). GATE1 is controlled by CB only if VULO < VIN < VOVLO. 8 8 GND Ground 10 10 GATE2 pFET Gate Drive Output, Open Drain. When CB is high, GATE2 is low (P2 is on). When CB is low, GATE2 is high impedance (P2 is off). |
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