The Chargers (3-4) trailed 27-10 in the second quarter. They had lost 11 of their past 12 road games.
Linebacker Denzel Perryman delivered two key plays late in the game. Perryman's interception of Matt Ryan's pass for Julio Jones set up Lambo's tying 33-yard field goal with 18 seconds remaining in regulation.
Perryman's fourth-and-1 stop on running back Devonta Freeman gave San Diego the ball at Atlanta's 43 for the Chargers' winning drive. Perryman grabbed Freeman's feet behind the line for the key tackle on the Falcons' gamble.
Atlanta took the lead with three straight second-quarter touchdowns before San Diego launched its comeback.
Melvin Gordon ran for 68 yards and two touchdowns and added a 5-yard scoring catch early in the fourth quarter, cutting Atlanta's lead to 30-27.
Atlanta's Matt Bryant missed his attempt for a 58-yard field goal on the final play of regulation. The Falcons (4-3) have lost two straight.
Jones had nine catches for 174 yards.
PROTEST: Five San Diego players raised their clenched right fists as their protest during the national anthem. Standing together on the San Diego sideline, offensive linemen D.J. Fluker, Chris Hairston and Joe Barksdale and linebacker Joshua Perry held up their fists as they stood. Offensive tackle Tyreek Burwell, inactive and not in uniform, also raised his fist as part of the protest.
There were no demonstrations from Falcons players.
200 AGAIN: Ryan passed for 273 yards for his NFL-record 46th consecutive game with more than 200 yards passing. He threw a 17-yard scoring pass to tight end Jacob Tamme in the second quarter.
INJURIES: Chargers defensive tackle Caraun Reid was carted off with a left knee injury in the first quarter and did not return. Reid had a teammate fall on his leg on a Falcons completion to tight end Levine Toilolo.
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