Datasheet LT1505 (Analog Devices) - 4

LT1505
ELECTRICAL CHARACTERISTICS The
●
denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25
°
C. VCC = 18V, VBAT = 12.6V, VCLN = VCC (LT1505), no load on any outputs unless otherwise noted. PARAMETER CONDITIONS MIN TYP MAX UNITS Voltage Amplifier VA
Transconductance (Note 3) Output Current from 50µA to 500µA 0.21 0.6 1.0 mho Output Source Current VFB = VPROG = VREF + 10mV 1.1 mA VFB Input Bias Current At 0.5mA VA Output Current, TA < 70°C – 10 25 nA (3 CELL, 4.1V, 4.2V Are Not Connected, VBAT2 = 0V)
Current Limit Amplifier CL1
Turn-On Threshold 0.5mA Output Current 87 92 97 mV Transconductance Output Current from 50µA to 500µA 0.5 1 3 mho CLP Input Current 0.5mA Output Current 1 3 µA CLN Input Current 0.5mA Output Current 0.8 2 mA
Input P-Channel FET Driver (INFET)
INFET “On” Clamping Voltage (VCC – VINFET) VCC ≥ 11V ● 6.5 7.8 9 V INFET “On” Driver Current VINFET = VCC – 6V ● 8 20 mA INFET “Off” Clamping Voltage (VCC – VINFET) VCC Not Connected, IINFET < – 2µA 1.4 V INFET “Off” Drive Current VCC Not Connected, (VCC – VINFET) ≥ 2V – 2.5 mA
Charging Completion Flag (Comparator E6)
Charging Completion Threshold (Note 6) Measured at VRS1, VCAP = 2V (Note 7) 14 20 28 mV Threshold On CAP Pin Low to High Threshold ● 3.3 4.2 V High to Low Threshold ● 0.6 V VCAP at Shutdown VSHDN = Low (Shutdown) ● 0.13 0.3 V FLAG (Open Collector) Output Low VCAP = 4V, IFLAG < 1mA ● 0.3 V FLAG Pin Leakage Current VCAP = 0.6V ● 3 µA
Gate Drivers (TGATE, BGATE)
VGBIAS 11V < VCC < 24V, IGBIAS ≤ 15mA ● 8.4 9.1 9.6 V VSHDN = Low (Shutdown) ● 1 3 V VTGATE High (VTGATE – VSW) ITGATE ≤ 20mA, VBOOST = VGBIAS – 0.5V ● 5.6 6.6 V VBGATE High IBGATE ≤ 20mA ● 6.2 7.2 V VTGATE Low (VTGATE – VSW) ITGATE ≤ 50mA ● 0.8 V VBGATE Low IBGATE ≤ 50mA ● 0.8 V Peak Gate Drive Current 10nF Load 1 A Gate Drive Rise and Fall Time 1nF Load 25 ns VTGATE, VBGATE at Shutdown VSHDN = Low (Shutdown) ● 1 V ITGATE = IBGATE = 10µA
Note 1:
Absolute Maximum Ratings are those values beyond which the life
Note 6:
See “Lithium-Ion Charging Completion” in the Applications of a device may be impaired. Information Section.
Note 2:
Tested with Test Circuit 1.
Note 7:
Tested with Test Circuit 3.
Note 3:
Tested with Test Circuit 2.
Note 8:
ISPIN keeps switching on to keep VBAT regulated when battery is not present to avoid high surge current from C
Note 4:
When V OUT when battery is CC and battery voltage differential is low, high duty factor inserted. is required. The LT1505 achieves a duty factor greater than 99% by skipping cycles. Only when VBOOST drops below the comparator A2
Note 9:
Above undervoltage threshold switching is enabled. threshold will TGATE be turned off. See Applications Information.
Note 10:
Do not connect VCC directly to VIN (see Figure 1). This connection
Note 5:
When the system starts, C2 (boost cap) has to be charged up to will cause the internal diode between VBAT and VCC to be forward-biased drive TGATE and to start the system. The LT1505 will keep TGATE off and and may cause high current to flow from VIN. When the adapter is turn BGATE on for 0.2µs at 200kHz to charge up C2. Comparator A2 removed, VCC will be held up by the body diode of M1. senses VBOOST and switches to the normal PWM mode when VBOOST is above the threshold. 1505fc 4